PCF8885TS/1,118 - NXP Semiconductors

1. General description

The integrated circuit PCF8885 is a capacitive 8-channel touch and proximity sensor that

uses a patented (EDISEN) method to detect a change in capacitance on remote sensing

plates. Changes in the st atic cap acit ances (as opposed to dynamic capacit ance changes)

are automatically compensated using continuous auto-calibration. Remo te sensing plates

(for example, cond ucti ve fo ils ) can be conn ected to the IC 1 using coaxial cable. The eight

input channels operate independently of each other. There is also a built-in option for a

matrix arrangement of the sensors: interrupt generation only when two channels are

activated simultaneously, suppression of additional channel outputs when two channels

are already active.

2. Features and benefits

Dynamic touch and proximity sensor with 8 sensor channels

Support for matrix arrangement of sensors

Sensing plates can be connected remotely

Adjustable response time

Adjustable sensitivity

Continuous auto-calibration

Digital processing meth od

Can cope with up to 6 mm of acrylic glass

Direct and latching switch modes

I2C Fast-mode Plus (Fm+) compatible interface

Two I2C-bus addresses

Cascading of two ICs possible

Interrupt signaling over I2C-bus

Interrupt output

Large voltage operating range (VDD = 2.5V to 5.5V)

Sleep mode (IDD < 100 nA)

Low-power battery operation possible (IDD ~10A)

Operating temperature range (Tamb = 40 C to +85 C)

Available in TSSOP28 and SOIC28 package

PCF8885

Capacitive 8-channel touch and proximity sensor with

auto-calibration and very low power consumption

Rev. 3 — 17 March 2014 Product data sheet

1. The definition of the abbreviations and acronyms used in this data sheet can be found in Section 22 on page 38.

Product data sheet Rev. 3 — 17 March 2014 2 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

3. Applications

Replacing mechanical switches

Hermetically sealed keys on a keyboard

Switches for medical applications

Switches for use in explosive environments

Audio control: on/off, channel, volume

Sliders and wheel-switches

Vandal proof switches

Switches in or under the upholstery, leather, handles, mats, carpets, tiles and glass

Switches for home automation

Use of standard metal sanitary parts (for example a tap) as switch

Portable communication and entertainment units

White goods control panel

4. Ordering information

4.1 Ordering options

5. Marking

Table 1. Ordering information

Type number Package

Name Description Version

PCF8885TS TSSOP28 plastic small outline package; 28 leads;

body width 4.4 mm PCF8885TS

Table 2. Ordering options

Product type number Orderable part number Sales item

(12NC) Delivery form IC

revision

PCF8885TS/1 PCF8885TS/1,118 935296171118 tape and reel, 13 inch 1

Table 3. Marking codes

Type number Marking code

PCF8885TS/1 PCF8885TS

Product data sheet Rev. 3 — 17 March 2014 3 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

6. Block diagram

Fig 1. Block diagram of PCF8885

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Product data sheet Rev. 3 — 17 March 2014 4 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

7. Pinning information

7.1 Pinning

7.2 Pin description

Top view. For mechanical details, see Figure 26 on page 35.

Fig 2. Pin configuration for TSSOP28 (PCF8885TS)

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Table 4. Pin description

Input or input/output pins must always be at a defined level (VSS or VDD) unless otherwise specified.

Symbol Pin Type Description

PCF8885TS

CLK_OUT 1 output clock output for chip cascading and

synchronization

VDD(INTREGD)[1] 2 supply internal regulated supply reference voltage

IN7 to IN0 3 to 10 analog

input/output sensor input, channel 0 to 7[2]

CPC7 to CPC0 11 to 18 analog

input/output reservoir capacitor, channel 0 to 7[2]

VSS 19[3] supply ground supply voltage

SCL 20 input serial clock line

SDA 21 input/output serial data line

TEST 22 input test pin;

must be connected to VSS

A0 23 input I2C subaddress LSB[4]

SLEEP 24 input sleep mode;

connect to VDD to force the circuit into

low-power sleep mode

INT 25 output interrupt output

Product data sheet Rev. 3 — 17 March 2014 5 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

[1] The internal regulated supply voltage output must be decoupled with a decoupling capacitor to VSS.

[2] If a channel is not used, the apropriate sensor input line has to be left open, the corresponding CPCn has to

be connected to VSS and the channel should be disabled in the MASK register (see Table 11 on page 15).

[3] The die paddle (exposed pad) is connected to VSS and should be electrically isolated.

[4] Used to address two devices, for example: low address 3Ah, high address 3Bh.

VDD 26 supply supply voltage

INT_IN 27 input interrupt input for chip cascading;

connect to VDD if not used

CLK_IN 28 input clock input;

for the secondary chip when the primary

chip provides the clock signal

Table 4. Pin description …continued

Input or input/output pins must always be at a defined level (VSS or VDD) unless otherwise specified.

Symbol Pin Type Description

PCF8885TS

Product data sheet Rev. 3 — 17 March 2014 6 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

8. Functional description

The sensing plates have to be connected to the sensor input pins IN0 to IN7. The

discharge times (tdch) on the sensor input pins, are compared to the discharge time

(tdch(ref)) of an internal RC timing element. The comparison is done sequen tially for each

sensor input pin. The RC timing circuits are periodically charged from VDD(INTREGD) and

then discharged via a resistor to VSS. The charge-discharge cycle for each channel is

governed by the samp lin g ra te (fs). The channels are sampled sequentially, while the

reference element is activated at the sampling point of each channel (see timing diagram

in Figure 3).

When the voltage of an RC combination falls below the level Vref, the appropriate

comparator output changes. The logic following the comparators determines which

comparator switched first. If the reference comparator switched first, then a pulse is given

on CUP. If the sensor comparator switched first, then a pulse is given on CDN. Figure 4

illustrates the functional principle of the PCF8885.

The pulses control the charge on the external capacitors CCPC on pins CPC0 to CPC7.

Every time a pulse is given on CUP, the capacitor CCPC is charged through a current

source (Isource) from VDD(INTREGD) for a fixed tim e causing th e volt age on CCPC to rise by a

small increment. Likewise when a pulse occurs on CDN, capacitor CCPC is discharged

through a current sink (Isink) towards ground for a fixed time, cau s ing the vo ltage on CCPC

to fall by a small d ecrement. The volt age on CCPC controls an additional current sink (ICPC)

that causes the capacitance attached to the input pins IN[0:7] to be discharged more

quickly. This arrangemen t constitutes a closed loop control system, that constantly tr ies to

equalize the discharge time (tdch) with the reference discharge time (tdch(ref)). In the

equilibrium state, the discharge times are nearly equal and the pulses alternate between

CUP and CDN.

For this example, the oscillator frequency and the clock division factor have been set to result in a 1 kHz sampling frequency.

Fig 3. Timing diag ram of se ns o r sa mpling

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Product data sheet Rev. 3 — 17 March 2014 7 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

The counter following this logic counts the pulses CUP or CDN respectively. The counter

is reset every time the pulse sequence changes from CUP to CDN or the other way round .

The outputs OUT0 to OUT7 are only activated when 64 cons ecu tive pulses occur re d on

CUP. Low-level interference or slow changes in the input capacitance do not cause the

output to switch.

Various measures, such as asymmetrical charge and discharge steps, are taken to

ensure that the output switches off correctly. A special st art-up circuit ensures that the

device reaches equilibrium quickly when the supply is attached.

The sampling rate (fs) is derived from the internally generated oscillator frequency. The

oscillator frequency can be adjusted within a specified range by programming the

CLKREG register (see Table 10 on p age 14).

The status of the output signals OUT0 to OUT7 is stored in the SENS register (see

Table 9 on page 13). An interrupt is generated on changes of the sensor states.

Fig 4. Functional diag ram of se ns or operation

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Product data sheet Rev. 3 — 17 March 2014 8 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

9. Commands

The operation of the PCF88 85 can be controll ed by 12 commands and four co nfiguration-

and status-registers (see Section 10 on page 10). Several configuration settings can be

programmed using single commands without associated data transfer. The configuration

registers can only be programmed using the write-clock and write-mask commands.

9.1 Command overview

9.2 Command: soft-reset

Reset takes place during power-on of the circuit. There is no external hardware reset

input.

During operation, the device can be reset using the soft-reset command. The sensor

channels and all registers are reset to the default values and the int-over-I2C mode is

terminated. It does not af fect the st ate of the analog section except fo r those functions that

are controlled by configuration bits.

9.3 Commands: Sleep and wake-up

Sleep mode is implemented to save power during periods where no sensor activity is

expected or supported.

In sleep mode, most of the circuit parts are put in power-down mode, in particular all

analog blocks consuming static and dynamic power. This includes the oscillator, thus no

internal activity remains. Also the voltage regulator is powered down, to reduce its

standalone power consu m pt ion .

Table 5. Commands of PCF8885

Command Operation

code Description Transfer

type Reference

soft-reset 00000000 brings chip to reset state command Section 9.2,

Section 10.2.2.2

clear-INT 00000011 deactivates interrupt generation on pin

INT command Section 10.2.2.1

sleep 0000010 1 enter sleep mode command Section 9.3

wake-up 00000110 enter active mode command

write-config 00110000 write configuration register write 1 byte Section 10.2

read-config 00110011 read configuration register read 1 byte

write-clock 00110101 write clock setting register write 1 byte Section 10.4

read-clock 00110110 read clock setting register read 1 byte

write-mask 00111001 write the mask register write 1 byte Section 10.5

read-mask 00111010 read the mask register read 1 byte

int-over-I2C 00111100 put the device in int-over-I2C mode command Section 10.2.2.1

read-sensor - read sensor state register and clears

the INT line direct read Section 9.4,

Section 10.2.2.1

Product data sheet Rev. 3 — 17 March 2014 9 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

During sleep mode, the register configuration is maintained and the device remains

responsive to I2C commands. The charges in the CPC capacitors however cannot be

guaranteed, as there is no limitation on the duration of the sleep mode. Therefore the

analog part has to perform a normal start-up phase, including the fast start procedure for

the CPC capacitor charging.

Sleep mode is entered wh en the sleep command is received from the system co ntroller or

when the SLEEP pin is set to HIGH. Resume is done by the wake-up command, or by

setting the SLEEP pin to LOW.

The hardware sleep mechanism using the SLEEP pin and the software sleep mechanism

using the sleep or wake-up commands are independent of each other:

•If the device was put to sleep using the sleep command, a wake-up command

resumes the operation. It cannot be resumed by activating the SLEEP pin.

•If the device was put to sleep by setting pin SLEEP to HIGH, then pin SLEEP must be

set to LOW to resume operation. It cannot be resumed with the wake-up command.

9.4 Command: read-sensor

The read-sensor command is the main transaction to read the actual state information of

the sensor state register SENS.

If the R/W bit (LSB of the I2C slave address byte, see Table 12 on page 20) is set logic 1

the PCF8885 regards the transaction as the read-sensor command. The read-sensor

command transaction su pports a repeated r eading of the SENS register (see Section 10.3

on page 13). When two circuits are used in a cascaded configuration, they alternately

return their SENS register content in a single transaction

The protocol s fo r the re peated read mode and the alterna ting read mode are de scribed in

Section 13.7 on page 21.

Product data sheet Rev. 3 — 17 March 2014 10 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

10. Registers

The PCF8885 h as four registers storing the configuration and the status information of the

device.

10.1 Register overview

10.2 Register: CONFIG

Table 6. Register overview

The bit position labeled as x is not relevant; if read, it can be either logic 0 or logic 1.

name Bit Default

value

76543210

CONFIG OPM[1:0] SWM KM[1:0] VROF INTM MSKMODE 00000000

SENS CH[7:0] 00000000

CLKREG CLO CLI x FRQC[1:0] FRQF[2:0] 00x01100

MASK MSK[7:0] 11111111

Table 7. CONFIG - configuration register bit description

Bit Symbol Value Description Reference

7 to 6 OPM[1:0] main operation mode Section 10.2.1.1

00[1] stand-alone device

01 secondary-chip in a

cascade

10 primary-chip in a cascade

11 unused

5 SWM switching mode Section 10.2.1.2

0[1] direct switching mode:

sensor release clears the

corresponding bit in the

SENS register

1 latching mode :

reading SENS register

clears bits in the SENS

4 to 3 KM[1:0] key-press mode Section 10.2.1.3

00[1] N-key mode:

each sensor activity is

reflected in the SENS

01 2-key mode:

only first two keys are

visible in the SENS register

10 1-key mode:

only first key-press is visible

in the SENS register

11 unused

Product data sheet Rev. 3 — 17 March 2014 11 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

[1] Default value.

All bits in this register can be written and read with the write-config and read -config

commands.

10.2.1 Operating modes

10.2.1.1 Main operating modes

The PCF8885 can operate in three operating modes: as a stand-alone device or in a

cascade as a primary-chip or a secondary-chip (see Table 8).

[1] Default operating mode after power-on.

The operating modes are implemented to support the application of two PCF8885 in the

system (see Section 13.8 on page 22).

10.2.1.2 Switching modes

There is a one to one relationship between the channels IN[0:7] and the bits in the SENS

switching modes supported:

2 VROF voltage regulation Section 11

0[1] voltage regulation on

1 voltage regulation off

1 INTM interrupt generation mode Section 10.2.2

0[1] an interrupt is generated by

each bit changed in the

SENS register (press and

release)

1 an interrupt is generated by

each bit set in the SENS

0 MSKMODE channel maski ng mode Section 10.5.1

0[1] normal power:

masked out channels

remain operational

1 low power:

masked out chann els are

powered do w n

Table 7. CONFIG - configuration register bit description …continued

Bit Symbol Value Description Reference

Table 8. Main operatin g modes

Conditions of Main operating modes

Stand-alone[1] Primary-chip Secondary-chip

clock source internal oscillator internal oscillator clock input

oscillator enabled enabled disabled

clock output pin CLK_OUT disabled enabled disabled

clock input pin CLK_IN disabled disabled enabled

Product data sheet Rev. 3 — 17 March 2014 12 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

Direct mode — In direct mode, the sensor state is directly reflected in the SENS register.

When the sensor is activated, the corresponding bit in the SENS register is immediately

set logic 1. When the sensor is released, the bit is cleared (set logic 0) agai n. The bits are

even cleared if the SENS register has not yet been read by the system controller.

Latching mode — In latching mode , ever y activated sensor sets the correspon ding bit in

the SENS register logic 1. When the sensor is released, the SENS register is unaffected.

Reading the SENS regi st er clears (se t log i c 0) thos e bits, whose se nsor is not activated

anymore.

After reset, the PCF8885 is set to direct switching mode.

10.2.1.3 Key-press modes

There are three key-press modes implemented in the PCF8885: N-key, 1-key, and 2-key

mode.

N-key mode — In N-key mode, each sensor activity is reflected in register SENS

according to the configured switching mode. The N-key mode is the default key-press

mode after reset.

1-key mode — In 1-key mode, only the first sensor activation sets the corresponding bit

in register SENS. All further activations of the other sensors are su ppressed at the SENS

accidentally because they are arranged next to the activated sensor.

The 1-key mode supports sensor matrix arrangements with two PCF8885, where one chip

is attached to the co lumns and one to the rows (primar y-chip and secondary-chip). Sensor

activation sets 1 bit for the column and 1 bit for the row in the SENS register of the

appropriate chip. Each activation of a sensor raises an interrupt. The system controller

must handle the situation where the INT is raised before the second sensor in the matrix

has been activated.

2-key mode — In 2-key mode, only the two first sensor activations set the corresponding

bits in register SENS. All further activations of the other sensors are suppressed at the

SENS register boundary. This mode supports in particular the matrix arrangement of

sensors using only one PCF8885, as illustrated in Figure 25 on page 33. In this way,

sensors in a matrix are masked out, which are activated accidentally because they are

arranged next to the intended sensors. This mode properly handles a delay in sensor

activation due to unequal sensor capacitance or area (non-centric sensor touching, and

so on) as long as the intended sensors react befo re sensors which are activated

accidentally. In 2-key mode, the INT output is only activated after 2 bits have been set in

the SENS register.

10.2.2 Interrupt generation

The PCF8885 provides two mechanisms to inform the system controller that a sensor

activity has been detected.

10.2.2.1 Interrupt output INT

The PCF8885 has an interrupt output, INT, to flag to the system controller that a

capacitive event has been detected. The controller can then fetch the sensor state by

reading the SENS register over the I2C-bus.

The interrupt generation is con trolled by th e INTM bit in th e CONFIG r egister (see Table 7

on page 10).

Product data sheet Rev. 3 — 17 March 2014 13 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

•If INTM is logic 0 (default), then the change (s et or clear) of ea ch bit in re giste r SENS

activates the INT output.

•If INTM is logic 1, then only sensor press events, resulting in bits being set logic 1 in

the SENS register, activate the INT output. Sens or release events, which cause the

corresponding bit in SENS to be cleared (set logic 0), do not activate the INT output.

In 2-key mode, the INT output is only activated after 2 bits have been set in the SENS

The interrupt is automatically cleared when the system controller read s the SENS register .

Alternatively the INT can be cleared by using th e clear-INT command, without readin g the

actual sensor state.

10.2.2.2 Interrupt over the I2C-bus

In applications where the sensing plates are re mote from the microc ontroller, the interrupt

line can be saved by enabling the interrupt over I2C-bus.

The PCF8885 provides the feature of interrupt over the I2C-bus. The PCF8885 then

behaves l ike an I2C master with restricted functionality . The interrupt is signaled by setting

a START condition immediately followed by a STOP condition. It is illustrated in Figure 5.

No further I2C master capabilities are supported.

The system controller has to detect the START-STOP condition and react accordingly.

The interrupt over the I2C-bus can be enabled with the int-over-I2C command and

disabled with the soft-reset command.

In interrupt over the I2C-bus mode, the functionality of the INT output continues to work as

described in Section 10.2.2.1.

10.3 Register: SENS

[1] Default value.

All bits in this register are read-only and can be read with the re ad-sensor co mma nd (se e

Section 9.4).

Fig 5. Interrupt over the I2C-bus

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Table 9. SENS - sensor state register bit description

Bit Symbol Value Description

7 to 0 CH[7:0] 00000000[1] to

11111111 sensor state of the respective channels IN7 to

IN0

Product data sheet Rev. 3 — 17 March 2014 14 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

10.4 Register: CLKREG

[1] Default value.

[2] Should always be written with logic 0 and if read, it can be either logic 0 or logic 1.

All bits in this register can be written and read with the write-clock and read-clock

commands.

10.4.1 Clock generation and frequency adjustment

The PCF8885 contains an integrated oscillator as main clock source. With the values of

FRQF[2:0], the oscillator frequency can be tuned (see Equation 1).

(1)

Table 10. CLKREG - clock setting register bit description

Bit Symbol Value Description

7 CLO CLK_OUT switch

0[1] CLK_OUT disabled (unless IC is in

primary-chip mode)

1 CLK_OUT enabled

6 CLI CLK_IN switch

0[1] CLK_IN disabled (unless IC is in

secondary-chi p mode)

1 CLK_IN enabled, internal oscillator is

powered do w n

5- -

[2] unused

4 to 3 FRQC[1:0] clock frequency, coarse setting

01[1]

2 to 0 FRQF[2:0] oscillator tuning

000

001

010

011

100[1]

101

110

111

fclk fosc 64=

fclk fosc 16=

fclk fosc 4=

fclk fosc

fosc 0.5 fosc nom

=

fosc 0.625 fosc nom

=

fosc 0.75 fosc nom

=

fosc 0.875 fosc nom

=

fosc 1f

osc nom

=

fosc 1.25 fosc nom

=

fosc 1.5 fosc nom

=

fosc 1.75 fosc nom

=

fosc mf

osc nom

=

Product data sheet Rev. 3 — 17 March 2014 15 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

The values of m can be varied in the ra nge 0.5 m1.75, where m = 1.0 corresponds to

the default value of F R QF[ 2:0 ] = 100.

The internal clock frequency (fclk) is derived from the oscillator frequency with Equation 2:

(2)

where the values for n are 1, 4, 16, or 64 and can be selected with FRQC[1:0]. The sensor

sampling frequency (fs) is derived from the internal clock frequency with Equation 3:

(3)

The eight sensors are sampled sequentially, which results in a default sensor sampling

rate fs.

In secondary-chip mode, the inter nal clock generator is stopped , and the circuit is clocked

from the CLK_IN input pin.

The tuning of the oscillator frequency and the programmable clock divider (see Figure 6)

allows changing the sen so r samp ling rat e, th e ad jus tm en t of the re ac tio n tim e and th e

power consumption of the PCF8885 over a wide range.

10.5 Register: MASK

[1] Default value.

All bits in this register can be written and read with the write-mask and read-mask

commands.

10.5.1 Channel masking

The channel masking register MASK allows individual sensor channels to be enabled or

disabled for particular applications or certain modes (for example only the on/off sensor

should be active).

Fig 6. Oscillator block diagram

fclk fosc n=

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Table 11. MASK - channel enable mask register bit description

Bit Symbol Value Description

7 to 0 MSK[7:0] 00000000 to

11111111[1] enable or disable the respective sensor

channels IN0 to IN7

0 sensor channel is disabled

1 sensor channel is enabled

Product data sheet Rev. 3 — 17 March 2014 16 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

•When bit MSKMODE in register CONFIG (see Table 7) is set logic 0, then the

disabled channels are continuo usly sampled, but switching event s are not refle cted in

•When bit MSKMODE in register CONFIG (see Table 7) is set logic 1, only channels

which are enabled are sampled. Reducing the number of sampled channels also

reduces the power consumption.

When a channel becomes newly enabled, the fast start-up method (see Section 12) is

used to reach the functional state quickly.

Product data sheet Rev. 3 — 17 March 2014 17 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

11. Power architecture

The circuit has an integrated voltage regulator, supplied by pin VDD. The regulator

provides an inte rn al VDD(INTREGD) supply of nominally 2.8 V.

If a stable and noise free external supply voltage with 2.5 V < VDD(ext) < 3.3 V is available

in the system, VDD(INTREGD) can be provided from an external source (see Figure 7). In

this ca se VDD and VDD(INTREGD) must both be connecte d to VDD(ext). To reduce the current

consumption, the internal voltage regulator should be shut down by setting bit VROF

logic 1 (see Table 7 on page 10).

While the analog p art of the circuit is power ed from VDD(INTREGD), the I2C interface and the

registers are powered from VDD. Therefore the I2C interface remains accessible in sleep

mode, and the register values are maintained when VDD(INTREGD) is powered off.

Figure 8 illustrates the behavior of the integrated voltage regulator. The gray area covers

the operational range of the PCF8885. The analog part of the circuit and the switch logic is

powered from VDD(INTREGD). The I2C interface and the registers are powered from VDD.

Therefore the I 2C interface remains accessible in sleep mod e, and the r egister va lues are

maintained when VDD(INTREGD) is powered off.

2.5 V < VDD(ext) <3.3V.

Fig 7. Connection of VDD(ext)

Fig 8. Integrated voltage regulator behavior

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Product data sheet Rev. 3 — 17 March 2014 18 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

12. Start-up procedure

After power-on the registers in the VDD domain are reset, which includes the VROF bit

controlling the voltage regulator. The regulator is therefore enabled, and the VDD(INTREGD)

domain is powered on. As soon as a sufficient VDD(INTREGD) level is reached, the

Power-On Reset (POR) is released.

After release of the POR in the VDD(INTREGD) domain, the circuit starts with the sensor

sampling in the fast start mode (increased charge-pump currents quickly charge the CPC

capacitors close to their target value). As soon as the capacitor voltages are close to the

target value, the fast start phase is terminated, and the capacitors are charged in fine

steps to the final value. When this state is reached, the logic enables the up and down

counters, and the sensors are operational.

This start-up mechanism is executed independently for each channel.

13. Characteristics of the I2C-bus

The PCF8885 has an I2C serial interface which operates as a slave receiver or

transmitter. SDA and SCL are the data I/O and clock lines for the se rial I2C Interface. SDA

is used as an input or as an open-drain output. SDA is actively pulled LOW and is

passively held HIGH by the external pull-up resistor on the I2C-bus.

In order to provide high link robustness, the I2C interface of the PCF8885 is Fast-mode

compatible and provides a robust addressing and command scheme.

13.1 Bit transfer

One data bi t is transferred durin g each clock pulse . The data o n the SDA line must remain

stable during the HIGH period of the clock pulse as changes in the data line at this time

are interpreted as a control signal (see Figure 9).

13.1.1 START and STOP conditions

Both data and clock lines remain HIGH when the bus is not busy.

A HIGH-to-LOW change of the data line, while the clock is HIGH, is defined as the START

condition (S).

A LOW-to-HIGH change of the data line, while the clock is HIGH, is defined as the STOP

condition (P).

Fig 9. Bit transfer

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Product data sheet Rev. 3 — 17 March 2014 19 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

The START an d STOP conditions are shown in Figure 10.

13.2 System configuration

A device generating a message is a transmitter; a device receiving a message is the

receiver. The device that controls the message is the master; and the devices which are

controlled by the master are the slaves. The system configuration is shown in Figure 11.

13.3 Acknowledge

The number of data bytes tran sf er re d be tween the START and STOP conditions from

transmitter to receiver is unlimited. Each byte of 8 bits is followed by an acknowledge

cycle.

•A slave receiver, which is addressed, must generate an acknowledg e after the

reception of each byte.

•A master receiver must generate an acknowledge after the reception of each byte that

has been clocke d ou t of th e sl av e tra n sm i tte r.

•The device that acknowledges must pull-down the SDA line during the acknowledge

clock pulse, so that the SDA line is stable LOW during the HIGH period of the

acknowledge related clock pulse (set-up and hold times must be considered).

•A master receiver must signal an end of data to the transmitter by not generating an

acknowledge on the last byte that has been clocked out of the slave. In this event, the

transmitter mus t leave the data line HIGH to enable the master to generate a STOP

condition.

Acknowledgement on the I2C-bus is shown in Figure 12.

Fig 10. Defin itio n of START and STO P condition s

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Product data sheet Rev. 3 — 17 March 2014 20 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

13.4 I2C-bus subaddress

Device selection depends on the I2C-bus slave address, on the transferred command

data, and on the hardware subaddress.

Two I2C-bus slave addresses are used to address the PCF8885 (see Table 12).

The least significant bit of the slave address is bit R/W (see Table 13).

Bit 1 of the slave address is defined by connecting input A0 to either V SS (logic 0) or VDD

(logic 1). Therefor e, two instance s of PCF8885 can be distinguish ed on the same I2C-bus.

13.5 I2C-bus protocol

The I2C-bus protocol is shown in Figure 13. The sequence is initiated with a START

condition (S) from the I2C-bus master which is followed by the slave address.

Fig 12. Acknowledgem ent on the I2C-bus

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Table 12. I2C slave address byte

Bit Slave address

MSB 6543210

LSB

Slave address 010000A0R/W

Table 13. R/W-bit description

R/W Description

0 write data

1 read data

Fig 13. I2C-bus protocol write mode

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Product data sheet Rev. 3 — 17 March 2014 21 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

After acknowledgement, a command is sent, and after a further acknowledge a data byte

is transmitted. After the last data byte, the I2C-bus master issues a STOP condition (P).

Alternatively a START may be asserted to RESTART an I2C-bus access.

13.6 Fast-mode Plus (Fm+) support

The Fast-mode Plus specification is suppo r ted . Bes i de s pr ov idin g a hig h tran sm issio n

speed, the main characteristic of Fast-mode Plus is th e increased drive strength , allowing

lower impedance buses to be driven, and therefore less noise sensitive. Details on the

Fast-mode Plus specification are given in Ref. 15 “UM10204”.

13.7 Reading sensor data

The PCF8885 support s direct r eading of the sensor state fr om the SENS register. If - after

sending the address - the R/W bit is immediately set to logic 1 without sending a

command, the circ uit recognizes that it mu st imm e dia te ly re tu rn the cont en t of th e SENS

When the transaction, after reading the SENS register, is not terminated with a STOP bit,

the PCF8885 repeatedly sends the content of SENS again. This provides a facility to

observe the sensor activity continuously. This transaction is illustrated in Figure 15.

Using two PCF8885 in a cascade (see Section 13.8), one has to be the primary-chip and

the other the seco ndary-chi p. When the dir ect re ad transactio n is executed in a cascade d

configuration, the primary-chip transmits its SENS content register immediately after the

address byte, followed by the secondary-chip transmitting its SENS register content.

If the transaction - after reading the two SENS registers - is not terminated with a STOP

bit, the primary-chip and the secondary-chip continue sending the content of the SENS

registers alternately. Such a transaction is illustrated in Figure 16.

Fig 14. Reading sensor data

Fig 15. Continuously reading sensor data

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Product data sheet Rev. 3 — 17 March 2014 22 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

It must be noted, that for this alternate data transfer only one PCF8885 has to be

addressed. By definition the primary-chip mu st be a ddr essed (A0 bit in the add re ss set to

logic 0). In this particular case, the secondary-chip reacts on the address of the

primary-chip. For all other transactions targeting the secondary-chip, it must be properly

addressed with A0 set to logic 1.

13.8 Device cascading

T wo PCF8885 device s can be connected to the same I2C-bus, which facilit ates up to 8 8

keypads.

The device provides the following features to guarantee robust operation and to simplify

the system design using two devices:

•The 7-bit I2C addres s consists of 6 fixed bits an d 1 selectable bit. The level exte rn ally

applied to pin A0 (VDD or VSS) defines the LSB of the I2C slave address. In this way,

two PCF8885 can be addressed on the same bus without the need for different hard

coded I2C addresses.

•The sensor activity can be sy nchronized, so that interference between the sensors of

the different chips is avoided. One chip is considered to be the primary-chip. It

provides the sample clock on pin CLK_OUT. The other chip is considered to be the

secondary-chip. It uses the clock provided by the primary-chip instead of the internal

clock. The primary-chip samples the sensors on the rising edge of the internal sample

clock. The CLK_IN signal is inverted to derive the sample clock in the secondary-chip.

Therefore the secondary-chip samples its sensors on the negative ed ge of the sample

clock of the primary-chip. In this way, no s imu ltaneous se nso r sam pling occurs.

Primary-chip or secondary-chip modes are e nabled by programming the configuration

•The interrupt signal can be cascaded. The INT output of the primary-chip can be

connected to the INT_IN input of the secondary-chip. The INT output of the

secondary-chip is then an OR’ed combination of the two interrupts.

•If two devices are cascaded and the int-over-I2C mode is desired, then it is suf ficient

to put the secondary-chip in int-over-I2C mode. The primary-chip still signals an

interrupt over the INT output to the INT_IN input of the secondary-chip.

Figure 25 on page 33 illustrates a typical example of an application using two PCF8885

circuits.

Fig 16. Reading sensor data, alternately from primary-chip and secondary-chip

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Product data sheet Rev. 3 — 17 March 2014 23 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

14. Internal circuitry

15. Safety notes

Fig 17. Device protection diagram

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This device is sensitive to ElectroStatic Discharge (ESD). Observe precautions for handling

electrostatic sensitive devices.

Such precautions are described in the ANSI/ESD S20.20, IEC/ST 61340-5, JESD625-A or

equivalent standards.

Product data sheet Rev. 3 — 17 March 2014 24 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

16. Limiting values

[1] Pass level; Human Body Model (HBM) according to Ref. 10 “ JESD22-A114”.

[2] Pass level; Charged-Device Model (CDM), according to Ref. 11 “JESD22-C101”.

[3] Pass level; latch-up testing, according to Ref. 12 “JESD78” at maximum ambient temperature (Tamb(max)).

[4] According to the store and transport requirements (see Ref. 17 “UM10569”) the devices have to be stored at a temperature of +8 C to

+45 C and a humidity of 25 % to 75 %.

Table 14. Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter Conditions Min Max Unit

VDD supply voltage 0.5 +8.0 V

VDD(INTREGD) internal regulated supply voltage 0.5 +6.5 V

VIinput voltage on all input pins 0.5 +6.5 V

ISS ground supply current 50 +50 mA

ISDA current on pin SDA 30 +30 mA

II/O(n) input/output current on any other pin 10 +10 mA

Ptot total power dissipation - 100 mW

VESD electrostatic discharge voltage HBM [1] -2000 V

CDM [2] -750 V

Ilu latch-up current [3] - 100 mA

Tstg storage temperature [4] 60 +125 C

Tamb ambient temperature op erating device 40 +85 C

Product data sheet Rev. 3 — 17 March 2014 25 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

17. Static characteristics

[1] See Figure 8 for an illustration of the voltage regulation behavior and the related parameters.

[2] Idle state is the steady state after completed power-on, without any mode change and without any activity on the sensor plates, and the

voltages on the reservoir capacitors CCPC are settled.

[3] In case of an ESD event, the value may increase slightly.

[4] The insulation resistance of the capacitor should be at least 5 G.

Table 15. Static characteristics

VDD = 2.5V to 5.5V, V

SS =0V, T

amb =





C to +85



C; unless otherwise specified; min and max values are not production

tested, but verified on sampling basis.

Symbol Parameter Conditions Min Typ Max Unit

VDD supply voltage 2.5 - 5.5 V

VDD(ext) external supply voltage VDD connected to

VDD(INTREGD); internal

regulator disabled

2.5 - 3.3 V

VDD(INTREGD) internal regulated supply

voltage [1]

2.5 2.9 3.3 V

external supplied 2.5 - 3.3 V

IDD supply current idle state; fs= 1 kHz [2] -1020 A

IDD(sleep) sleep mode supply current - 100 500 nA

Digital inputs (CLK_IN, A0, INT_IN, TEST)

VIL LOW-level input voltage VSS -0.3V

DD V

VIH HIGH-level input voltage 0.7VDD -V

DD V

Digital outputs (INT, CLK_OUT)

VOL LOW-level output voltage IO=0.5mA V

SS -0.2V

DD V

VOH HIGH-level output voltage IO= 0.5 mA 0.8VDD -V

DD V

Analog pins (IN0 to IN7 and CPC0 to CPC7)

VCPC voltage on pin CPC usable control range VSS +0.5 - V

DD(INTREGD) 0.5 V

Cin input capacitance sensing plate and parasitic 10 - 40 pF

I2C interface pins (SDA, SCL)

VIL LOW-level input voltage 0.5 - 0.3VDD V

VIH HIGH-level input voltage 0.7VDD -5.5 V

IOL LOW-level output current VDD =5.0V; V

OL =0.4V 20 - - mA

ILleakage current [3] -0- A

Cicapacitance for each I/O pin - - 10 pF

External component s

CCPC capacitance on pin CPC [4] 22 100 470 nF

Cdec decoupling capacitance on pins VDD(INTREGD) and

VDD; ceramic chip capacitor -100- nF

Product data sheet Rev. 3 — 17 March 2014 26 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

fs=1kHz.

(1) VDD =2.5V.

(2) VDD =3.3V.

(3) VDD =5.5V.

Fig 18. IDD with respect to temperature

(1) VDD =2.5V.

(2) VDD =3.3V.

(3) VDD =5.5V.

Fig 19. IDD with respect to sampling frequency (internal clock)

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Product data sheet Rev. 3 — 17 March 2014 27 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

(1) VDD =2.5V.

(2) VDD =3.3V.

(3) VDD =5.5V.

Fig 20. IDD with respect to sampling frequency (external clock)

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Product data sheet Rev. 3 — 17 March 2014 28 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

18. Dynamic characteristics

[1] Default value.

[2] For switching, 64 consecutive CUP pulses are needed.

Table 16. Dynamic characteristics

VDD = 2.5V to 5.5V, V

SS =0V, T

amb =



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

C; unless otherwise specified; min and max values are not production

tested, but verified on sampling basis.

Symbol Parameter Conditions Min Typ Max Unit

System timing

tstartup start-up time CCPC =100nF; f

s= 1 kHz;

Cin =40pF -200-ms

fosc oscillator frequency in ternal RC oscillator;

FRQF[2:0] = 100 [1] 58 80 112 kHz

tsw switching time fs = 1 kHz [2] -64-ms

I2C interface characteristics (SDA, SCL)

tSP pulse width of spikes that must be

suppressed by the input filter 0- 50ns

fSCL SCL clock frequency 0 - 1000 kHz

tHD;STA hold time (repeated) START condition 0.26 - - s

tSU;STA set-up time for a repeated STAR T condition 0.26 - - s

tLOW LOW period of the SCL clock 0.5 - - s

tHIGH HIGH period of the SCL clock 0.26 - - s

tHD;DAT data hold time 0 - - ns

tSU;DAT data set-up time 50 - - ns

trrise time of both SDA and SCL signals - - 120 ns

tffall time of both SDA and SCL signals - - 120 ns

tSU;STO set-up time for STOP condition 0.26 - - s

tBUF bus free time between a STOP and START

condition 0.5 - - s

Cbcapacitive load for each bus line - - 550 pF

tVD;DAT data valid time - - 0.45 s

tVD;ACK data valid acknowledge time - - 0.45 s

tw(int) interrupt pulse width interrupt over I2C-2-s

Product data sheet Rev. 3 — 17 March 2014 29 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

18.1 I2C interface timing

(1) VDD = 2.5 V; Ci=41pF.

(2) VDD = 3.3 V; Ci=41pF.

(3) VDD = 5.5 V; Ci=41pF.

(4) VDD = 3.3 V; Ci=10pF.

Fig 21. Start-up time with respect to CCPC

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Product data sheet Rev. 3 — 17 March 2014 30 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

19. Application information

19.1 Single device application

(1) Pin CLK_IN can be tied to VSS or left open.

Fig 23. Single device application diagram

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Product data sheet Rev. 3 — 17 March 2014 31 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

19.2 28 sensor grid application in 2-key mode

Fig 24. Application diagram for 28 sensors in 2-key mode

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Product data sheet Rev. 3 — 17 March 2014 32 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

Table 17. Input combinations for a 28 sensor grid in 2-key mode

Sensor Inputs

IN7 IN6 IN5 IN4 IN3 IN2 IN1 IN0

100000011

200000101

300001001

400010001

500100001

601000001

710000001

800000110

900001010

10 00010010

11 00100010

12 01000010

13 10000010

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16 00100100

17 01000100

18 10000100

19 00011000

20 00101000

21 01001000

22 10001000

23 00110000

24 01010000

25 10010000

26 01100000

27 10100000

28 11000000

Product data sheet Rev. 3 — 17 March 2014 33 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

19.3 Cascaded application

(1) If the SLEEP pin is not used, it must be connected to VSS.

(2) Pin CLK_IN can be tied to VSS or left open.

(3) Instead of the INT pin, interrupt over I2C-bus can be used. If the INT pin is not used, it must be left open.

Fig 25. Cascaded application diagram

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Product data sheet Rev. 3 — 17 March 2014 34 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

Figure 25 shows the typical connections for a general application using two chips. For

simplicity, the sensors attached to the secondary-chip are not shown in this diagram. The

sensors of the secondary-chip can be arranged independently of the sensors of the

primary-chip or combined in a common larger matrix.

Both chips use different I2C addresse s programmed by the voltage le vel applied to pin A0.

The primary-chip has A0 connected to ground; the secondary-chip has A0 connected to

VDD(ext). In this way, each circuit is addressed individually.

In this case, the primary-chip is programmed to use the internal oscillator as clock

reference. The primary-chip is also programmed to enable the clock output. The

secondary-chip is programmed to use the clock output from the primary-chip as input

clock. The internal oscillator of the secondary-chip is shut down to save power in this

mode.

The interrupt output INT of the pr im ar y-c hip is rout ed to th e INT _I N input of the

secondary-chip, where it is OR’ed with the interrupt state of the secondary-chip.

The sensing plate cap acit ances ma y consist of a small met al area , for example be hind an

isolating layer. Illustrated in Figure 25 is a 4 4 sensor arrangement. In this configuration,

a sensor touch always excites two sensor plates at the same time.

The sensing plates are connected to a coaxial cable (for remote sensors) or a shielded

connection, which in turn is connected to the input pin IN. The connection capacitance

contributes to the input cap acit ance an d must not be neglected. An internal low pass filter

(not shown) is used to reduce RF interferen ce. An additional l ow pass filter con sisting of a

resistor RF and capacitor CF can be added to the input to improve RF immunity further

than required. For good performance, the total amount of capacitance on the input

(Cs+C

CABLE +C

F) should b e in th e p ro per r an ge, the op timum poin t bein g a round 30 pF.

Even if the external filtering is not required, placing CF can help to bring the input

capacitance to an optimal value. These conditions allow the control loop to adapt to the

static capacitance on CS and to compensat e fo r slow changes in the sensin g pl ate

capacitance. A higher capacitive input loading is possible, if an additional discharge

resistor RC is used. Resistor RC simply reduces the discharge time su ch that th e inter nal

timing requirements can be fulfilled.

The sensitivity of the sensors can be influenced by the sensing plate area and capacitors

CCPC. The sensitivity is redu ce d wh en C CPC is reduced. When maximum sensitivity is

desired, CCPC can be increased, but it also increases sensitivity to interference. The

CPC[0:7] pins have high impedance and are sensitive to leakage currents.

Remark: CCPC should be a high-quality foil or ceramic capacitor, for example an

X7R type.

For the choice of proper component values for a given application, the component

specifications in Section 17 on p age 25 must be followed.

Product data sheet Rev. 3 — 17 March 2014 35 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

20. Package outline

Fig 26. Package outline PCF8885TS (TSSOP28)

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Product data sheet Rev. 3 — 17 March 2014 36 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

21. Soldering of SMD packages

This text provides a very brief insight into a complex technology. A more in-depth account

of soldering ICs can be found in Application Note AN10365 “Surface mount reflow

soldering description”.

21.1 Introduction to soldering

Soldering is one of the most common methods through which packages are attached to

Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both

the mechanical and the electrical connection. There is no single soldering method that is

ideal for all IC packages. Wave soldering is often preferred when through-hole and

Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not

suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high

densities that come with increased miniaturization.

21.2 Wave and reflow soldering

W ave soldering is a joinin g technology in which the joint s are made by solder coming from

a standing wave of liquid solder. The wave soldering process is suitable for the following:

•Through-hole components

•Leaded or leadless SMDs, which are glued to the surface of the printed circuit board

Not all SMDs can be wave soldered. Packages with solder balls, and some leadless

packages which have solder lands underneath the body, cannot be wave soldered. Also,

leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,

due to an increased probability of bridging.

The reflow soldering process involves applying solder paste to a board, followed by

component placement and exposure to a temperature profile. Leaded packages,

packages with solder balls, and leadless packages are all reflow solderable.

Key characteristics in both wave and reflow soldering are:

•Board specifications, including the board finish, solder masks and vias

•Package footprints, including solder thieves and orientation

•The moisture sensitivity level of the packages

•Package placement

•Inspection and repair

•Lead-free soldering versus SnPb soldering

21.3 Wave soldering

Key characteristics in wave soldering are:

•Process issues, such as application of adhesi ve and flux, clinching of leads, board

transport, the solder wave parameters, and the time during which components are

exposed to the wave

•Solder bath specifications, including temperature and impurities

Product data sheet Rev. 3 — 17 March 2014 37 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

21.4 Reflow soldering

Key characteristics in reflow soldering are:

•Lead-free ve rsus SnPb soldering; note th at a lead-free reflow process usua lly leads to

higher minimum peak temperatures (see Figure 27) than a SnPb process, thus

reducing the process window

•Solder paste printing issues including smearing, release, and adjusting the process

window for a mix of large and small components on one board

•Reflow temperature profile; this profile includes preheat, reflow (in which the board is

heated to the peak temperature) and cooling down. It is imperative that the peak

temperature is high enoug h for the solder to make reliable solder joint s (a solder paste

characteristic). In addition, the peak temperature must be low enough that the

packages and/or boards are not damaged. The peak temperature of the package

depends on package thickness and volume and is classified in accordance with

Table 18 and 19

Moisture sensitivity precautions, as indicated on the packing, must be respected at all

times.

Studies have shown that small packages reach higher temperatures during reflow

soldering, see Figure 27.

Table 18. SnPb eutectic process (from J-STD-0 20D)

Package thickness (mm) Package reflow temperature (C)

Volume (mm3)

< 350  350

< 2.5 235 220

 2.5 220 220

Table 19. Lead-free process (from J-STD-020D)

Package thickness (mm) Package reflow temperature (C)

Volume (mm3)

< 350 350 to 2000 > 2000

< 1.6 260 260 260

1.6 to 2.5 260 250 245

> 2.5 250 245 245

Product data sheet Rev. 3 — 17 March 2014 38 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

For further information on temperature profiles, refer to Application Note AN10365

“Surface mount reflow soldering description”.

22. Abbreviations

MSL: Moisture Sensitivity Level

Fig 27. Temperature profiles for large and small components

001aac844

temperature

time

minimum peak temperature

= minimum soldering temperature

maximum peak temperature

= MSL limit, damage level

peak

temperature

Table 20. Abbreviations

Acronym Description

CMOS Complementary Metal Oxide Semiconductor

HBM Human Body Model

IC Integrated Circuit

MM Machine Model

MOS Metal Oxide Semiconductor

MOSFET Metal–Oxide–Semiconductor Field-Effect Transistor

MSL Moisture Sensitivity Level

PCB Printed-Circuit Board

RC Resistance-Capacitance

RF Radio Frequency

SMD Surface Mount Device

Product data sheet Rev. 3 — 17 March 2014 39 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

23. References

[1] AN10365 — Surface mount reflow soldering description

[2] AN10832 — PCF8883 - capacitive proximity switch with auto-calibration

[3] AN10853 — Handling precautions of ESD sensitive devices

[4] AN11122 — Water and cond en sa tio n sa fe touc h se ns in g with the NX P

capacitive touch sensors

[5] AN11157 — Capacitive touch sensin g with high EMC performance, Application Note

[6] AN11155 — General design guidelines for the NXP capacitive sensors

[7] IEC 60134 — Rating syst ems for electronic tubes and valves and analogous

semiconductor devices

[8] IEC 61340-5 — Protection of electronic devices from electrostatic phenomena

[9] IPC/JEDEC J-STD-020D — Moisture/Reflow Sensitivity Classification for

Nonhermetic Solid State Surface Mount Devices

[10] JESD22-A114 — Electrostatic Discharge (ESD) Sensitivity Testing Human Body

Model (HBM)

[11] JESD22-C10 1 — Field-Induced Charged-Device Model Test Method for

Electrostatic-Discharge-Withstand Thresholds of Microelectronic Components

[12] JESD7 8 — IC Latch-Up Test

[13] JESD625-A — Requirements for Handling Electrostatic-Discharge-Sensitive

(ESDS) Devices

[14] SNV-FA-01-02 — Marking Formats Integrated Circuits

[15] UM102 04 — I2C-bus specification and user manual

[16] UM105 05 — OM11057 quick start guide

[17] UM105 69 — Store and transport requirements

[18] UM106 64 — PCA8885 and PCF8885 evaluation board OM11056

[19] UM107 20 — User manual for the TFT touch demo board OM11058

Product data sheet Rev. 3 — 17 March 2014 40 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

24. Revision history

Table 21. Revision history

Document ID Release date Data sheet status Chang e notice Supersedes

PCF8885 v.3 20140317 Product data sheet - PCF8885 v.2

Modifications: •The format of this data sheet has been redesigned to comply with the new identity

guidelines of NXP Semiconductors.

•Legal texts have been adapted to the new company name where appropriate.

•Emphasized the X7R statement

•Changed product and ordering information Section 4

•Adjusted Figure 3, Figure 4, Figure 13, Figure 15

•Added Table 13

•Added Section 15

PCF8885 v.2 20121025 Product data sheet - PCF8885 v.1

PCF8885 v.1 20120221 Product data sheet - -

Product data sheet Rev. 3 — 17 March 2014 41 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

25. Legal information

25.1 Data sheet status

[1] Please consult the most recently issued document before initiating or completing a design.

[2] The term ‘short data sheet’ is explained in section “Definitions”.

[3] The product status of de vice(s) descr ibed in th is docume nt may have cha nged since this docume nt was publis hed and ma y dif fer in case of multiple devices. The latest product status

information is available on the Internet at URL http://www.nxp.com.

25.2 Definitions

Draft — The document is a draft version only. The content is still under

internal review and subject to formal approval, which may result in

modifications or additions. NXP Semiconductors does not give any

representations or warranties as to the accuracy or completeness of

information included herein and shall have no liab ility for the consequences of

use of such information.

Short data sheet — A short data sheet is an extract from a full data sheet

with the same product type number(s) and tit le. A short data sh eet is intended

for quick reference only and shou ld not be rel ied u pon to cont ain det ailed and

full information. For detailed and full information see the relevant full data

sheet, which is available on request via the local NXP Semiconductors sales

office. In case of any inconsistency or conflict with the short data sheet, the

full data sheet shall pre vail.

Product specificat ion — The information and data provided in a Product

data sheet shall define the specification of the product as agreed between

NXP Semiconductors and its customer, unless NXP Semiconductors and

customer have explicitly agreed otherwise in writing. In no event however,

shall an agreement be valid in which the NXP Semiconductors product is

deemed to off er functions and qualities beyond those described in the

Product data sheet.

25.3 Disclaimers

Limited warr a nty and liability — Information in this document is believed to

be accurate and reliable. However, NXP Semiconductors does not give any

representations or warranties, expressed or implied, as to the accuracy or

completeness of such information and shall have no liability for the

consequences of use of such information. NXP Se miconductors takes no

responsibility for the content in this document if provided by an inf ormation

source outside of NXP Semiconductors.

In no event shall NXP Semiconductors be liable for any indirect, incident al,

punitive, special or consequ ential damages (including - wit hout limitatio n - lost

profits, lost savings, business interruption, costs related to the removal or

replacement of any products or rework charges) whethe r or not such

damages are based on tort (including negligence), warranty, breach of

contract or any other legal theory.

Notwithstanding any damages that customer might incur for any reason

whatsoever, NXP Semiconductors’ aggregate and cumulat ive liability toward s

customer for the products described herein shall be limited in accordance

with the Terms and conditions of commercial sale of NXP Semiconductors.

Right to make changes — NXP Semiconductors reserves the right to make

changes to information published in this document, including without

limitation specifications and product descriptions, at any time and without

notice. This document supersedes and replaces all informa tion supplied prior

to the publication hereof .

Suitability for use — NXP Semiconductors products are not designed,

authorized or warranted to be suitable for use in life support, life-critical or

safety-critical systems or equipment, nor in applicat ions where failure or

malfunction of an NXP Semiconductors product can reasonably be expected

to result in perso nal injury, death or severe property or environmental

damage. NXP Semiconductors and its suppliers accept no liability for

inclusion and/or use of NXP Semiconducto rs products in such equipment or

applications and ther efore such inclu sion and/or use is at the cu stomer’s own

risk.

Applications — Applications that are described herein for any of these

products are for illustrative purposes only. NXP Semiconductors makes no

representation or warranty tha t such application s will be suitable for the

specified use without further testing or modification.

Customers are responsible for the design and ope ration of their applications

and products using NXP Semiconductors product s, and NXP Semiconductors

accepts no liability for any assistance with applications or cu stomer product

design. It is customer’s sole responsibility to determine whether the NXP

Semiconductors product is suit able and fit for the custome r’s applications and

products planned, as well as fo r the planned application and use of

customer’s third party customer(s). Customers should provide appropriate

design and operating safeguards to minimize the risks associated with their

applications and products.

NXP Semiconductors does not accept any liability related to any default,

damage, costs or problem which is based on any weakness or default in the

customer’s applications or products, or the application or use by custo mer’s

third party customer(s). Customer is responsible for doing all necessary

testing for th e customer’s applications and product s using NXP

Semiconductors products in order to avoid a default of the applications and

the products or of the application or use by customer’s third p arty

customer(s). NXP does not accept any liability in this respect.

Limiting values — Stress above one or more limiting values (as defined in

the Absolute Maximum Ratings System of IEC 60134) will cause permanent

damage to the device. Limiting values are stress ratings only and (proper)

operation of the device at these or any other conditions above those given in

the Recommended operating conditions section (if present) or the

Characteristics sections of this document is not warranted. Constant or

repeated exposure to limiting values will permanent ly and irreversibly affect

the quality and reliability of the device.

Terms and conditions of commercial sale — NXP Semiconductors

products are sold subject to the general terms and conditions of commercial

sale, as published at http://www.nxp.com/profile/terms, unless otherwise

agreed in a valid written individua l agreement. In case an individual

agreement is concluded only the ter ms and conditions of the respective

agreement shall apply. NXP Semiconductors hereby expressly objects to

applying the customer’s general terms and conditions with regard to the

purchase of NXP Semiconductors products by customer.

No offer to sell or license — Nothing i n this document may be interpreted or

construed as an of fer t o sell product s that is open for accept ance or t he grant,

conveyance or implication of any license under any copyrights, patents or

other industrial or intellectual property rights.

Document status[1][2] Product status[3] Definition

Objective [short] data sheet Development This document contains data from the objective specif ication for product development.

Preliminary [short] dat a sheet Qualification This document contains data from the preliminary specification.

Product [short] dat a sheet Production This document contains the prod uct specification.

Product data sheet Rev. 3 — 17 March 2014 42 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

Export control — This document as well as the item(s) described herein

may be subject to export control regulations. Export might require a prior

authorization from competent authorities.

Quick reference data — The Quick reference data is an extract of the

product data given in the Limiting values and Characteristics se ctions of this

document, and as such is not complete, exhaustive or legally binding.

Non-automotive qualified products — Unless this data sheet expressly

states that this specific NXP Semiconductors product is a utomotive qualified,

the product is not suitable for automotive use. It i s neither qua lified nor test ed

in accordance with automotive testing or application requirements. NXP

Semiconductors accepts no liability for inclusion and/or use of

non-automotive qualified products in automotive equipment or applications.

In the event that customer uses the product for design-in and use in

automotive applications to automot ive specifications and standard s, customer

(a) shall use the product without NXP Semiconductors’ warranty of the

product for such automotive applicat ions, use and specifications, and (b)

whenever customer uses the product for automotive applications beyond

NXP Semiconductors’ specifications such use shall be solely at customer’s

own risk, and (c) customer fully indemnifies NXP Semiconductors for any

liability, damages or failed product claims resulting fr om customer design and

use of the product for automotive applications beyond NXP Semiconductors’

standard warranty and NXP Semiconductors’ product specifications.

Translations — A non-En glish (translated) version of a document is for

reference only. The English version shall prevail in case of any discrepancy

between the translated and English versions.

25.4 Trademarks

Notice: All referenced b rands, produc t names, service names and trademarks

are the property of their respect i ve ow ners.

I2C-bus — logo is a trademark of NXP Semi conductors N.V.

26. Contact information

For more information, please visit: http://www.nxp.com

For sales office addresses, please send an email to: salesaddresses@nxp.com

Product data sheet Rev. 3 — 17 March 2014 43 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

27. Tables

Table 1. Ordering information . . . . . . . . . . . . . . . . . . . . .2

Table 2. Ordering options. . . . . . . . . . . . . . . . . . . . . . . . .2

Table 3. Marking codes . . . . . . . . . . . . . . . . . . . . . . . . . .2

Table 4. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . .4

Table 5. Commands of PCF8885. . . . . . . . . . . . . . . . . . .8

Table 6. Register overview . . . . . . . . . . . . . . . . . . . . . .10

Table 7. CONFIG - configuration register

bit description . . . . . . . . . . . . . . . . . . . . . . . . .10

Table 8. Main operating modes . . . . . . . . . . . . . . . . . .11

Table 9. SENS - sensor state register

bit description . . . . . . . . . . . . . . . . . . . . . . . . . .13

Table 10. CLKREG - clock setting register

bit description . . . . . . . . . . . . . . . . . . . . . . . . .14

Table 11. MASK - channel enable mask register

bit description . . . . . . . . . . . . . . . . . . . . . . . . .15

Table 12. I2C slave address byte . . . . . . . . . . . . . . . . . . .20

Table 13. R/W-bit description . . . . . . . . . . . . . . . . . . . . . .20

Table 14. Limiting values . . . . . . . . . . . . . . . . . . . . . . . . .24

Table 15. Static characteristics . . . . . . . . . . . . . . . . . . . .25

Table 16. Dynamic characteristics . . . . . . . . . . . . . . . . . .28

Table 17. Input combinations for a 28 sensor

grid in 2-key mode . . . . . . . . . . . . . . . . . . . . . .32

Table 18. SnPb eutectic process (from J-STD-020D) . . .37

Table 19. Lead-free process (from J-STD-020D) . . . . . .37

Table 20. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .38

Table 21. Revision history . . . . . . . . . . . . . . . . . . . . . . . .40

Product data sheet Rev. 3 — 17 March 2014 44 of 45

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

28. Figures

Fig 1. Block diagram of PCF8885 . . . . . . . . . . . . . . . . . .3

Fig 2. Pin configuration for TSSOP28 (PCF8885TS). . . .4

Fig 3. Timing diagram of sensor sampling. . . . . . . . . . . .6

Fig 4. Functional diagram of sensor operation. . . . . . . . .7

Fig 5. Interrupt over the I2C-bus . . . . . . . . . . . . . . . . . .13

Fig 6. Oscillator block diagram. . . . . . . . . . . . . . . . . . . .15

Fig 7. Connection of VDD(ext) . . . . . . . . . . . . . . . . . . . . .17

Fig 8. Integrated voltage regulator behavior . . . . . . . . .17

Fig 9. Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Fig 10. Definition of START and STOP conditions. . . . . .19

Fig 11. System configuration. . . . . . . . . . . . . . . . . . . . . .19

Fig 12. Acknowledgeme nt on the I2C-bus . . . . . . . . . . . .20

Fig 13. I2C-bus protocol write mode . . . . . . . . . . . . . . . .20

Fig 14. Reading sensor data . . . . . . . . . . . . . . . . . . . . . .21

Fig 15. Continuously reading sensor data . . . . . . . . . . . .21

Fig 16. Reading sensor data, alternately from

primary-chip and secondary-chip. . . . . . . . . . . . .22

Fig 17. Device protection diagram. . . . . . . . . . . . . . . . . .23

Fig 18. IDD with respect to temperature . . . . . . . . . . . . . .26

Fig 19. IDD with respect to sampling frequency

(internal clock) . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Fig 20. IDD with respect to sampling frequency

(external clock) . . . . . . . . . . . . . . . . . . . . . . . . . .27

Fig 21. Start-up time with respect to CCPC. . . . . . . . . . . .29

Fig 22. I2C interface timing . . . . . . . . . . . . . . . . . . . . . . .29

Fig 23. Single device application di agram . . . . . . . . . . . .30

Fig 24. Application diagram for 28 sensors

in 2-key mode . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Fig 25. Cascaded application diagram . . . . . . . . . . . . . .33

Fig 26. Package outline PCF8885TS (TSSOP28). . . . . .35

Fig 27. Temperature profiles for large and small

components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

NXP Semiconductors PCF8885

Capacitive 8-channel touch and proximity sensor with auto-calibration

For more information, please visit: http://www.nxp.co m

For sales office addresses, please send an email to: salesaddresses@nxp.com

Date of release: 17 March 2014

Document identifier: PCF8885

Please be aware that important notices concerning this document and the product(s)

described herein, have been included in section ‘Legal information’.

29. Contents

1 General description. . . . . . . . . . . . . . . . . . . . . . 1

2 Features and benefits . . . . . . . . . . . . . . . . . . . . 1

3 Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

4 Ordering information. . . . . . . . . . . . . . . . . . . . . 2

4.1 Ordering options. . . . . . . . . . . . . . . . . . . . . . . . 2

5 Marking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

6 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3

7 Pinning information. . . . . . . . . . . . . . . . . . . . . . 4

7.1 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

7.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 4

8 Functional description . . . . . . . . . . . . . . . . . . . 6

9 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

9.1 Command overview . . . . . . . . . . . . . . . . . . . . . 8

9.2 Command: soft-reset . . . . . . . . . . . . . . . . . . . . 8

9.3 Commands: Sleep and wake-up . . . . . . . . . . . 8

9.4 Command: read-sensor . . . . . . . . . . . . . . . . . . 9

10 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

10.1 Register overview. . . . . . . . . . . . . . . . . . . . . . 10

10.2 Register: CONFIG . . . . . . . . . . . . . . . . . . . . . 10

10.2.1 Operating modes . . . . . . . . . . . . . . . . . . . . . . 11

10.2.1.1 Main operating modes . . . . . . . . . . . . . . . . . . 11

10.2.1.2 Switching modes . . . . . . . . . . . . . . . . . . . . . . 11

10.2.1.3 Key-press modes . . . . . . . . . . . . . . . . . . . . . . 12

10.2.2 Interrupt generation . . . . . . . . . . . . . . . . . . . . 12

10.2.2.1 Interrupt output INT . . . . . . . . . . . . . . . . . . . . 12

10.2.2.2 Interrupt over the I2C-bus. . . . . . . . . . . . . . . . 13

10.3 Register: SENS . . . . . . . . . . . . . . . . . . . . . . . 13

10.4 Register: CLKREG . . . . . . . . . . . . . . . . . . . . . 14

10.4.1 Clock generation and frequency adjustment . 14

10.5 Register: MASK . . . . . . . . . . . . . . . . . . . . . . . 15

10.5.1 Channel masking . . . . . . . . . . . . . . . . . . . . . . 15

11 Power architecture . . . . . . . . . . . . . . . . . . . . . 17

12 Start-up procedure. . . . . . . . . . . . . . . . . . . . . . 18

13 Characteristics of the I2C-bus . . . . . . . . . . . . 18

13.1 Bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

13.1.1 START and STOP conditions . . . . . . . . . . . . . 18

13.2 System configuration . . . . . . . . . . . . . . . . . . . 19

13.3 Acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . 19

13.4 I2C-bus subaddress . . . . . . . . . . . . . . . . . . . . 20

13.5 I2C-bus protocol . . . . . . . . . . . . . . . . . . . . . . . 20

13.6 Fast-mode Plus (Fm+) support . . . . . . . . . . . 21

13.7 Reading sensor data. . . . . . . . . . . . . . . . . . . . 21

13.8 Device cascading . . . . . . . . . . . . . . . . . . . . . . 22

14 Internal circuitry. . . . . . . . . . . . . . . . . . . . . . . . 23

15 Safety notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

16 Limiting values . . . . . . . . . . . . . . . . . . . . . . . . 24

17 Static characteristics . . . . . . . . . . . . . . . . . . . 25

18 Dynamic characteristics. . . . . . . . . . . . . . . . . 28

18.1 I2C interface timing. . . . . . . . . . . . . . . . . . . . . 29

19 Application information . . . . . . . . . . . . . . . . . 30

19.1 Single device application . . . . . . . . . . . . . . . . 30

19.2 28 sensor grid ap plication in 2-key mode . . . 31

19.3 Cascaded application. . . . . . . . . . . . . . . . . . . 33

20 Package outline. . . . . . . . . . . . . . . . . . . . . . . . 35

21 Soldering of SMD packages. . . . . . . . . . . . . . 36

21.1 Introduction to soldering. . . . . . . . . . . . . . . . . 36

21.2 Wave and reflow soldering. . . . . . . . . . . . . . . 36

21.3 Wave soldering . . . . . . . . . . . . . . . . . . . . . . . 36

21.4 Reflow soldering . . . . . . . . . . . . . . . . . . . . . . 37

22 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . 38

23 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

24 Revision history . . . . . . . . . . . . . . . . . . . . . . . 40

25 Legal information . . . . . . . . . . . . . . . . . . . . . . 41

25.1 Data sheet status. . . . . . . . . . . . . . . . . . . . . . 41

25.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

25.3 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . 41

25.4 Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . 42

26 Contact information . . . . . . . . . . . . . . . . . . . . 42

27 Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

28 Figures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

29 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

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Authorized Distributor

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PCF8885TS/1,118