WM0831CD - Wolfson Microelectronics Co., Ltd.

Lutton Court, Bernard T errace, Edinburgh EH8 9NX, UK

Tel: +44 (0) 131 667 9386 Fax: +44 (0) 131 667 5176

email: admin@wolfson.co.uk

www: http://www.wolfson.co.uk

W olfson Microelectronics

Production Data data sheets contain final

specifications current on publication date. Supply

of products conforms to W olfson Microelectronics

standard terms and conditions.

Production Data

Sept 1996 Rev 2.1

8-Bit ADCs with Serial Interface and

Differential or Dual Inputs

Description

WM0831 and WM0832 are 8-bit analogue to digital

converters (ADC) with serial I/O interfaces, providing a

choice of input configurations in 8-pin SO or DIP packages.

WM0831 has a differential input, also configurable as a

single ended input. A-D conversion results are serially

output on Data Out (DO) under the control of clock and chip

select inputs. The device has a separate voltage reference

input.

WM0832's two input multiplexer is configurable via the Data

In (DI) serial input, as two single ended inputs or a single

differential input. The voltage reference operates

ratiometrically and is internally connected to the VCC pin.

Conversion is initiated by bringing and holding chip select

low while providing a clock input. With WM0831's fixed

input configuration, the conversion result is output at DO on

the clock's falling edges in MSB to LSB order .

With WM0832's configurable input multiplexer, data is input

to DI on the rising edges of the clock to setup the Mux and

initiate conversion. Conversion results appear serially at

DO on the falling edges of the clock, first in MSB to LSB

order , and then repeated in LSB to MSB order.

WM0831/2 operate on 5V or 3.3V supply voltages and are

available in small outline and DIP packages for commercial

(0 to 70oC) and industrial (-40 to 85oC) temperature ranges.

Features

• Functionally Equivalent to National Semiconduc-

tor ADC0831 and ADC0832

• WM0831: Differential or single ended input

• WM0832: Two single ended inputs or a single

differential input

• Ratiometric reference input (fixed for WM0832)

• Serial I/O interface

• Input range 0 to Vcc with Vcc Reference

• 8 pin package, SO or DIP

• 5V and 3.3V variants

• Total Unadjusted Error: ± 1 LSB

• 8-bit resolution

• 32 µµ

µµ

µs conversion time at fclock = 250 kHz

Applications

• Embedding with remote sensors

• Equipment health monitoring

• Automotive

• Industrial control

Block Diagrams

WM0831 WM0832

GND

CH0

CH1

CLK

Vcc

REF

Start Conv

Mux Select

Input Latch

Internal CS

Control

Logic

Output Shift

Comparator

WM0832

DAC

SAR

Logic

Input

MUX

Control

Logic

Output

Latch

Comparator

WM0831

DAC

SAR

Logic

Differential

Input

IN+

IN-

REF

WM0831, WM0832

W olfson Microelectronics

WM0831, WM0832

Ordering InformationPin Configuration

Top View

8 pin P (DIP) and D (SO) packages

WM0831 WM0832

Absolute Maximum Ratings (note 1)

Supply Voltage, Vcc (note 2) . . . . . . . . . . . 6.5 V

Input voltage range:

Digital Inputs . . . . GND - 0.3 V, VCC + 0.3 V

Analogue inputs . . . GND - 0.3 V, VCC + 0.3 V

Input current, any pin (note 3) . . . . . . ± 5 mA

Total Input current for package . . . . . . ± 20 mA

Operating temperature range, TA . . . . TMIN to TMAX

WM083_C_ (C suffix) . . . . . . . . . 0oC to +70oC

WM083_I_ (I suffix) . . . . . . . . . . -40oC to +85oC

Storage Temperature . . . . . . . . - 65oC to +150oC

Soldering Information:

Lead Temperature 1.6 mm (1/16) from case

for 10 seconds: D or P package . . . . . . . 260oC

Recommended Operating Conditions (5V)

SYMBOL MIN NOMINAL MAX UNIT

Supply voltage VCC 4.5 5 5.5 V

High level input voltage VIH 2V

Low level input voltage VIL 0.8 V

Clock frequency fclock 10 600 KHz

Clock duty cycle (see Note 4) D clk 40 60 %

Pulse duration CS high twH(CS) 220 ns

Operating free-air temperature C suffix TA070

I Suffix TA-40 85

DEVICE TEMP. RANGE PACKAGE

WM0831CP 0oC to 70oC 8 pin plastic DIP

WM0831CD 0oC to 70oC 8 pin plastic SO

WM0831IP -40oC to 85oC 8 pin plastic DIP

WM0831ID -40oC to 85oC 8 pin plastic SO

WM0832CP 0oC to 70oC 8 pin plastic DIP

WM0832CD 0oC to 70oC 8 pin plastic SO

WM0832IP -40oC to 85oC 8 pin plastic DIP

WM0832ID -40oC to 85oC 8 pin plastic SO

DEVICE TEMP. RANGE P ACKAGE

WM0831LCP 0oC to 70oC 8 pin plastic DIP

WM0831LCD 0oC to 70oC 8 pin plastic SO

WM0831LIP -40oC to 85oC 8 pin plastic DIP

WM0831LID -40oC to 85oC 8 pin plastic SO

WM0832LCP 0oC to 70oC 8 pin plastic DIP

WM0832LCD 0oC to 70oC 8 pin plastic SO

WM0832LIP -40oC to 85oC 8 pin plastic DIP

WM0832LID -40oC to 85oC 8 pin plastic SO

5V devices

3.3V devices

W olfson Microelectronics 3

WM0831, WM0832

P ARAMETER SYMBOL TEST CONDITIONS MIN TYP MA X UNIT

Digital Inputs

High level output voltage VOH VCC = 4.75 V , IOH = -360 µA2.4 V

VCC = 4.75 V , IOH = -10 µA4.5 V

Low level output voltage VOL VCC = 5.25 V , IOH = 1.6 mA 0.4 V

High level input current IIH VIH = 5 V 0.005 1 µA

Low level input current IIL VIL = 0 V -0.005 -1 µA

High level output (source) IOH VOH = 0 V -6.5 -24 mA

current

Low level output (sink) current IOL VOL = VCC 826 mA

High impedance-state I OZ VO = 5 V 0.01 3 µA

output current (DO) VO = 0 V -0.01 -3 µA

Input capacitance CI5pF

Output capacitance Co5pF

Converter and Multiplexer

T otal unadjusted error TUE VREF = 5 V . (note 7) ±1 LSB

Differential Linearity (note 8) 8 Bits

Supply voltage variation error Vs(error) VCC = 4.75 V to 5.25 V ±1/16 ±1/4 LSB

Common mode error Differential mode ±1/16 ±1/4 LSB

Common mode input voltage VICR (note 9) GND-0.05 V

range VCC+0.05

Standby input leakage II(stdby) On-channel VI = 5 V at ON ch. 1 µA

current (note 10) Off-channel VI = 0 V at OFF ch. -1 µA

On-channel VI = 0 V at ON ch. -1 µA

Off-channel VI = 5 V at OFF ch. 1 µA

Conversion time tconv Excluding MUX addressing time 8 clock

periods

Reference Inputs

Input resistance to Ri(REF) Can only be tested for WM0831 1.3 2.4 5.9 kΩ

reference ladder

Total device

Supply current WM0831 ICC 0.6 1.25 mA

Supply current WM0832 ICC ( note 1 1) 2.5 4.7 mA

Timing Parameters

Setup time, CS low or tsu 350 ns

WM0832 data valid before

clock

Hold time, WM0832 data t h90 ns

valid after clock

Propagation delay time, MSB data first. CL = 100 pF 1500 ns

output data after clock tpd LSB data first. CL = 100 pF 600 n s

Output disable time, DO tdis CL = 10 pF, RL = 10 kΩ125 250 ns

after CS CL = 100 pF, RL = 2 kΩ500 ns

Electrical Characteristics (5V)

Vcc = 5V , VREF = 5V,fCLK = 250KHz, TA = T MIN to TMAX, tr = tf = 20 ns, unless otherwise stated.

W olfson Microelectronics

WM0831, WM0832

Recommended Operating Conditions (3.3V)

SYMBOL MIN NOMINAL MAX UNIT

Supply voltage VCC 2.7 3.3 3.6 V

High level input voltage VIH 2V

Low level input voltage VIL 0.8 V

Clock frequency (Vcc = 3.3V) fclock 10 600 KHz

Clock duty cycle (see Note 4) D clk 40 60 %

Pulse duration CS high twH(CS) 220 ns

Operating free-air temperature C suffix TA070

I Suffix TA-40 85

W olfson Microelectronics 5

WM0831, WM0832

P ARAMETER SYMBOL TEST CONDITIONS MIN TYP MA X UNIT

Digital Inputs

High level output voltage VOH VCC = 3V , IOH = -360 µA 2.4 V

VCC = 3 V , IOH = -10 µA 2.8 V

Low level output voltage VOL VCC = 3V, IOH = 1.6 mA 0.4 V

High level input current IIH VIH = 3.6 V 0.005 1 µA

Low level input current IIL VIL = 0 V -0.005 -1 µA

High level output (source) IOH VOH = 0 V, TA = 25oC6.515 mA

current

Low level output (sink) current IOL VOL = 0V, TA = 25oC816 mA

High impedance-state I OZ VO = 3.3V , TA = 25 oC 0.01 3 µA

output current (DO) VO = 0 V, TA = 25oC -0.01 -3 µA

Input capacitance CI5pF

Output capacitance Co5pF

Converter and Multiplexer

T otal unadjusted error TUE VREF = 3.3 V . (note 7) ± 1 LSB

Differential Linearity (note 8) 8 Bits

Supply voltage variation error Vs(error) VCC = 3 V to 3.6 V ±1/16 ±1/4 LSB

Common mode error Differential mode ±1/16 ±1/4 LSB

Common mode input voltage VICR (note 9) GND-0.05 V

range VCC+0.05

Standby input leakage II(stdby) On-channel VI =3.3V at ON ch. 1 µA

current (note 10) Off-channel VI =0 V at OFF ch. -1 µA

On-channel VI =0 V at ON ch. -1 µA

Off-channel VI =3.3V at OFF ch. 1 µA

Conversion time tconv Excluding MUX addressing time 8 clock

periods

Reference Inputs

Input resistance to Ri(REF) Can only be tested for WM0831 1.3 2.4 5.9 kΩ

reference ladder

Total device

Supply current WM0831 ICC 0.2 0.75 mA

Supply current WM0832 ICC ( note 1 1) 1.5 2.5 mA

Timing Parameters

Setup time, CS low or tsu 350 ns

WM0832 data valid before

clock

Hold time, WM0832 data t h90 ns

valid after clock

Propagation delay time, MSB data first. CL = 100 pF 200 500 n s

output data after clock tpd LSB data first. CL = 100 pF 80 200 ns

Output disable time, DO tdis CL = 10 pF, RL = 10 kΩ80 125 ns

after CS CL = 100 pF, RL = 2 kΩ250 ns

Electrical Characteristics (3.3V)

Vcc = 3.3V, fCLK = 250KHz, T A = TMIN to TMAX, tr = tf = 20 ns, unless otherwise stated.

W olfson Microelectronics

WM0831, WM0832

Notes:

1. Absolute Maximum Ratings are stress ratings only.

Permanent damage to the device may be caused by

continuously operating at or beyond these limits. De-

vice functional operating range limits are given under

Recommended Operating Conditions. Guaran-

teed performance specifications are given under Elec-

trical Characteristics at the test conditions specified.

2. All voltage values, except differential voltages are with

respect to the ground.

3. When the input voltage VIN at any pin exceeds the

power supply rails (GND > VIN > VCC) the absolute value

of current at that pin should be limited to 5 mA or less.

The 20 mA package input current limits the number of

pins that can exceed the power supply boundaries

with a 5 mA supply current to four .

4. A clock duty cycle range of 40% to 60% ensures

correct operation at all clock frequencies. For a clock

with a duty cycle outside these limits, the minimum time

the clock is high or low must be at least 666 ns, with

the maximum time for clock high or low being 60 ms.

5. All typical values are at VCC = 5 V, TA = 25oC for 5V

devices and VCC = 3.3V, TA = 25oC.

6. All parameters are measured under open-loop

conditions with zero common mode input voltage

(unless otherwise stated).

Electrical Characteristics (continued)

7. Total Unadjusted Error (TUE) is the sum of integral

linearity error , zero code error and full scale error over

the output code range.

8. A Differential linearity of "n" bits ensures a code width

exists to "n" bits. Hence a Differential Linearity of 8

bits for an 8 bit ADC guarantees no missing codes.

9 . For V IN(-) greater than or equal to VIN(+) the digital out-

put code will be 00 Hex. Connected to each analogue

input are two diodes which will forward conduct for a

diode drop outside the supply rails, V CC and GND. If an

analogue input voltage does not exceed the supply volt-

age by more than 50 mV, the output code will be cor-

rect. To use an absolute input voltage range of 0 to VCC

a minimum VCC - 0.05 V is required for all variations of

temperature. Care should be exercised when testing at

low VCC levels with a maximum analogue voltage as

this can cause the input diode to conduct, especially at

high temperature, and cause errors for analogue inputs

near full scale.

10. Standby input leakage currents, are currents going in

or out of the on or off channels when the ADC is not

performing conversion and the clock input is in a high

or low steady-state condition.

11. For WM0832 the reference current is included in the

supply current as VREF is internally connected to VCC.

W olfson Microelectronics 7

WM0831, WM0832

Test Circuits and Waveforms

Output Disable Time Voltage Waveforms and Test Circuits

Standby Leakage Current Test Circuit

Detailed Timing Diagrams

WM0832 Data Input Timing Data Output Timing

W olfson Microelectronics

WM0831, WM0832

Performance Data (typical)

Test conditions: VCC = 5V . VREF = 5V, Temp = 25oC, FCLK = 250KHz

WM0831: Total Unadjusted E rror

-1

-0.75

-0.5

-0.25

0.25

0.5

0.75

0 32 64 96 128 160 192 224 256

Code

Error (lsbs)

WM0832: Total Unadjusted E rror

-1

-0.75

-0.5

-0.25

0.25

0.5

0.75

0 32 64 96 128 160 192 224 256

Code

Error (lsbs)

W olfson Microelectronics 9

WM0831, WM0832

Functional Timing Diagrams

WM0831 Timing

WM0832 Timing

W olfson Microelectronics

WM0831, WM0832

Pin Descriptions

WM0831

Pin Name T y p e Function

1 CS Digital Chip Select

(active low)

2 I N+ Analogue input Positive differential

input

3 I N - Analogue input Negative differential

input

4 GND Supply Analogue and digital

ground

5VREF Analogue input Voltage reference

input

6 DO Digital input Data Output

7 CLK Digital input Clock input

8VCC Supply Positive supply

voltage

WM0832

Pin Name T y p e Function

1 CS Digital Chip Select

(active low)

2 CH0 Analogue input Channel 0 input to

multiplexer (MUX)

3 CH1 Analogue input Channel 1 input to

multiplexer (MUX)

4 GND Supply Analogue and

digital ground

5 D I Digital input Data input

6 DO Digital input Data Output

7 CLK Digital input Clock input

8VCC/VREF Supply/Analogue I/P Positive supply

voltage and

voltage(ratiometric)

reference input

Multiplexer / Package Options

Device Number of Analogue Channels Number of

No Single Ended Differential Package Pins

WM0831 1 1 8

WM0832 2 1 8

Functional Description

Input and Multiplexer Operation and Addressing

WM0831 has two inputs IN+ and IN- configured for

differential operation, single ended operation is achieved

by grounding IN- to an analogue common or GND.

WM0832 uses an input multiplexer scheme with two input

channels, configurable for single-ended or differential

operation. The single ended input uses the GND pin as its

analogue ground reference.

WM0831/2 uses a successive approximation routine to

perform A/D conversion and employs a sample data

comparator structure which always performs conversion

on a differential voltage. Conversion takes place on the

voltage difference between assigned “+” and “-” inputs and

the converter expects the “+” input to be the most positive,

if the “+” input is more negative than “-” then the converter

gives an all zeros output. Assignment of WM0832 inputs

is made for a single-ended signal between an “+” input

and (analogue) ground (GND), or for a differential input

between CH0 and CH1 inputs of either polarity.

For WM0832 prior to the start of every conversion the input

configuration is assigned during the MUX addressing

sequence by serially shifting data into the Data Input (DI) on

the second and third rising edges of the clock input. The

MUX address selects which analogue inputs are enabled,

either single-ended or differential. For differential inputs the

polarity of the inputs are also assigned. The MUX

addressing table gives full details of input assignments.

Because WM0831 has only one differential input of fixed

polarity it does not require addressing.

WM0832 MUX Addressing

MUX Address Channel Number

SGL/DIF ODD/EVEN 0 1

Differential MUX Mode

00+-

01-+

Single Ended MUX Mode

10+

11 +

W olfson Microelectronics 11

WM0831, WM0832

Initiating Conversion and the Digital Interface

WM0831 and WM0832 are controlled from a processor

via a Chip Select (CS) input and a serial interface

comprising Data Out (DO) and additionally for WM0832 a

Data In (DI) input.

For WM0831 conversion is initiated by pulling chip select

low and inputting a clock signal. On the clock's first falling

edge after CS is brought low, DO output comes out of

high impedance mode. On the second and subsequent

clock falling edges, to a total of nine, the conversion

result is output on DO in MSB to LSB order . WM0831 only

provides output data in MSB first order.

For WM0832 conversion is also initiated by pulling the chip

select (CS) line low and inputting a clock signal but MUX

addressing information has also to be input on DI. The

start bit and the MUX assignment bits on DI are clocked

in on the first three rising edges of the clock input which

may be generated by the processor or run continuously.

WM0832 uses two MUX assignment bits.

When the logic “1” start bit is clocked into the start

conversion location of the multiplexer input register the

analogue MUX inputs are selected. After 1/2 a clock

period delay to allow for the selected MUX output to settle

the conversion commences using the successive

approximation technique.

When conversion begins the A/D conversion result from

the output of the SARS comparator appears at the DO

output on each falling edge of the clock (see Functional

Timing Diagrams).

With the successive approximation A/D conversion

routine the analogue input is compared with the output of

a digital to analogue converter (DAC) for each bit by the

SARS comparator and a decision made on whether the

analogue input is higher or lower than the DAC output.

Successive bits, MSB to LSB, are input to the DAC and

remain in its input if the analogue comparison decides

the analogue input is higher than the DAC output, if not

the bit is removed from the DAC input. There is no sample

and hold. The input needs to be stable during Tconv period

(see Functional T iming Diagrams).

The output from the SARS comparator forms the

resulting input to the DAC and the A/D conversion output

on DO, and is read by the processor as conversion takes

place in MSB to LSB order. After 8 clock periods the

conversion is complete.

Functional Description (continued)

For WM0832 the 8 bits of the conversion are stored in an

output shift register , after a conversion has completed and

MSB first data has been output WM0832 automatically

shifts out LSB first data on the DO output.

CS must be held low through an entire conversion, all

internal registers are cleared when CS is high. To initiate

another conversion CS must make a high to low transition

and for WM0832 MUX address assignments input to DI.

For WM0832 the DI input and DO output can be tied

together and controlled via a bidirectional processor I/O

bit line.

Reference Input

The analogue input voltage range, Vmax to Vmin for

differential inputs is defined by the voltage applied to the

reference input with respect to GND. WM0832 is fixed in a

ratiometric mode with VREF internally tied to Vcc, WM0832

has a separate VREF pin and can be used in either

ratiometric applications or those requiring absolute

accuracy.

A ratiometric reference input, typically the Vcc, is the same

supply used to power analogue input circuitry and

sensors. In such systems under a given input condition

the same code will be output with variations in supply

voltage because the same ratio change occurs in both the

analogue and reference input to the A/D. When used in

applications requiring absolute accuracy a suitable time

and temperature stable voltage reference source should

be used.

The voltage source used to drive the reference input should

be capable of driving the 2.4 kΩ typical of the SAR

resistor ladder. The maximum input voltage to the

reference input is the Vcc supply voltage. The minimum

for WM0832 can be at least as low as 1 V to allow for

direct conversion of sensor outputs with output voltage

ranges less than 5 V.

W olfson Microelectronics

WM0831, WM0832

Functional Description (continued)

Analogue Inputs.

While sampling the analogue inputs short spikes of

current enter a “+” input and flow out of the corresponding

“-” input at the clock edges during conversion. This

current does not cause errors as it decays rapidly and the

internal comparator is strobed at the end of a clock

period. Care should be exercised if bypass capacitors are

used at the inputs, as an apparent offset error can be

caused by the capacitor averaging the input current and

developing a voltage across the source resistance.

Bypass capacitors should not be used with a source

resistance greater than 1kΩ.

In considering error sources, input leakage current will also

cause a voltage drop across the source resistance and

hence high impedance sources should be buffered.

In differential mode there is a 1/2 clock period interval be-

tween sampling the “+” and the “-” inputs. If there is a change

in common mode voltage during this interval an error could

notionally result.

For a sinusoidal common mode signal the error is given

b y: VERROR = VPEAK (2πfCM) (1/(2fCLK))

Where VPEAK = Peak common mode voltage

fCM = Common mode signal frequency

f CLK = Clock frequency .

W olfson Microelectronics 13

WM0831, WM0832

Package Descriptions

Plastic Small-Outline Package

Notes:

A. Dimensions in millimeters.

B. Complies with Jedec standard MS-012.

C. This drawing is subject to change without notice.

D. Body dimensions do not include mold flash or protrusion.

E. Dimension A, mould flash or protrusion shall not exceed 0.15mm. Body width, interlead flash or protrusions shall

not exceed 0.25mm.

NMinMax

8 4.80 5.00

14 8.55 8.75

16 9.80 10.00

Dimension 'A' Variations

D - 8 pins shown

0.51

0.33

1.75

1.35

0.25

0.10 Pin spacing

1.27 B.S.C.

1.27

0.40

0 to 8

0.25

0.19

0.50

0.25 x 45 NOM

6.20

5.80

4.00

3.80

Rev . 1 November 96

W olfson Microelectronics

WM0831, WM0832

Package Descriptions

Notes:

A. Dimensions are in inches

B. Falls within JEDEC MS-001( 20 pin package is shorter than MS-001)

C. N is the maximum number of terminals

D. All end pins are partial width pins as shown, except the 14 pin package which is full width.

Dimension 'A' V ariations

Dual-In-Line Package

N or P

Rev . 1 November 96

NMinMax

8 0.355 0.400

14 0.735 0.775

16 0.735 0.775

20 0.940 0.975

0.210 Max.

0.070 Max.

0.045

0.030

0.022

0.014

0.015

Min.

0.150

0.115

0.005

Min. Pin spacing

0.100 B.S.C.

Seating

plane

0.280

0.240

0.325

0.290

0.014

0.008

105

N/2