MAX3120ESA+T - Maxim Integrated

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General Description

The MAX3120 IrDA 1.2-compatible infrared transceiver

is optimized for battery-powered, space-constrained

applications. It consumes only 120µA while supporting

data rates up to 115kbps over a wide 3V to 5.5V oper-

ating range, and features a 10nA shutdown mode to

further extend battery life.

The MAX3120 reduces the space required for IrDA

applications by requiring a minimum of external compo-

nents: photodiode, infrared LED, and current-setting

resistor. Optical components are external to allow maxi-

mum flexibility in PC board design. The MAX3120 is

available in 8-pin µMAX and SO packages. The µMAX

package consumes half the board space of an 8-pin

SO.

Applications

IrDA Applications

Personal Digital Assistants (PDAs)

Palmtop Computers

Cell Phones

Hand-Held Equipment

Peripherals

Features

♦IrDA 1.2 Compatible: 2.4kbps to 115.2kbps

♦+3V to +5.5V Single-Supply Operation

♦Flexible Optics Selection and Layout

♦120µA Supply Current

♦10nA Shutdown Supply Current

♦200mA, High-Current Infrared LED Drive

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

________________________________________________________________

Maxim Integrated Products

RXD

LEDC

PGND

SHDNPINC

GND

VCC

TXD

MAX3120

µMAX/SO

TOP VIEW

19-1390; Rev 0; 10/98

PART

MAX3120CUA

MAX3120CSA

MAX3120EUA -40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

8 µMAX

8 SO

8 µMAX

Pin Configuration

Ordering Information

MAX3120ESA -40°C to +85°C 8 SO

MAX3120

RXD PINC

LEDC

TXD

+3.3V

VCC SHDN

GND PGND

MAX3100

SCLK

DIN

DOUT

VCC

GND PIN

DIODE

LED

Typical Operating Circuit

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC = +3.0V to +5.5V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C and VCC = +3.3V.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

(Referred to GND)

VCC...........................................................................-0.3V to +6V

TXD, SHDN, LEDC ...................................................-0.3V to +6V

RXD ............................................................-0.3V to (VCC + 0.3V)

PGND ....................................................................-0.1V to +0.1V

PINC....................................................................................10mA

Continuous LEDC Current.................................................200mA

Repetitive Pulsed LEDC Current

(<90µs, duty cycle <20%) ..........................................500mA

Continuous Power Dissipation (TA= +70°C)

µMAX (derate 4.1mW/°C above +70°C)....................330mW

SO (derate 5.88mW/°C above +70°C).......................471mW

Operating Temperature Ranges

MAX3120C_A....................................................0°C to +70°C

MAX3120E_A.................................................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +160°C

Lead Temperature (soldering, 10sec).............................+300°C

Data rate = 2.4kbps

TA= +25°C, SHDN = GND (Note 1)

Delay until maximum IR receiver data rate is

valid

Delay until ICC < 1µA

TA= +25°C, SHDN = VCC (Note 1)

VCC = 5.0V

VCC = 3.3V

(Note 3)

(Note 2)

ISINK = 200µA

VCC = 3.3V

CLOAD = 50pF

VCC = 5.0V

ISOURCE = 100µA

CONDITIONS

µs

190

IR Receiver Output Pulse Width

µs300Shutdown Disable Time

µs10Shutdown Time 375 µA

100

Ambient DC Current Rejection

mA0.0002 6Input Current Sensitivity nARMS

10INOISE

Equivalent Input Noise Current kbps2.4 115.2Supported Data Rates

ns50tr, tf

Output Rise and Fall Time

VCC -V

CC -

0.5 0.05

VOH

µA0.01 1.0ICC(SHDN)

Shutdown Supply Current µA120 200ICC

Supply Current

0.1 0.4VOL

Output Voltage

pF2CIN

Input Capacitance µA-1 1ILEAK

Input Leakage Current

V0.8VIL

Input Logic Threshold Low

2.0

VIH

Input Logic Threshold High 2.4

UNITSMIN TYP MAXSYMBOLPARAMETER

Data rate = 115.2kbps 18

DC CHARACTERISTICS

LOGIC OUTPUT (RXD)

LOGIC INPUTS (TXD, SHDN)

IR RECEIVER

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

_______________________________________________________________________________________

0.6

0.8

1.2

1.0

1.4

1.6

-40 10-15 35 60 85

LED DRIVER

ON-RESISTANCE vs. TEMPERATURE

MAX3120 TOC01

TEMPERATURE (°C)

RLEDC (Ω)

ILEDC = 100mA

VCC = 3.3V

VCC = 5V

100

120

110

130

140

-40 10-15 35 60 85

SUPPLY CURRENT

vs. TEMPERATURE

MAX3120 TOC02

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

VCC = 3V

VCC = 5V

105

115

110

125

120

130

135

3.0 4.03.5 4.5 5.0 5.5

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX3120 TOC03

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (µA)

200

100

400

300

500

600

100 250 300150 200 350 400

LEDC VOLTAGE

vs. LEDC CURRENT

MAX3120 toc04

LEDC CURRENT (mA)

VLEDC (mV)

VCC = 3.3V

VCC = 5V

PULSED AT

20% DUTY CYCLE

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

CONDITIONS UNITSMIN TYP MAXSYMBOLPARAMETER

Transmitter Rise Time tr10% to 90% of 200mA drive current 20 600 ns

Transmitter Fall Time tf90% to 10% of 200mA drive current 20 600 ns

Transmitter Output Resistance IOUT = 200mA 1.15 2.0 Ω

0.9 1.6

Off-Leakage Current 0.01 10 µA

VCC = 5.0V

VCC = 3.3V

IR TRANSMITTER

Note 1: All supply current measurements are made under the following conditions: no load at all outputs, input voltages at GND or

VCC, no PIN diode input current.

Note 2: Equivalent input current noise is calculated by dividing the output noise of the transimpedance amplifier by the midband

transimpedance gain.

Note 3: Sensitivity is measured with an IrDA-compliant input signal, where the data rate is within the Supported Data Rate, rise/fall

times are less than 600ns, and pulse widths are between 1.41µs and 3/16 of the baud rate.

ELECTRICAL CHARACTERISTICS (continued)

(VCC = +3.0V to +5.5V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at TA= +25°C and VCC = +3.3V.)

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

4 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

1.0

2.0

1.5

3.0

2.5

3.5

4.0

04020 60 80 100

RXD OUTPUT PULSE WIDTH

vs. DISTANCE

MAX3120 TOC07

DISTANCE (cm)

RXD PULSE WIDTH (µs)

TRANSMITTER POWER = 200mW/sr

INPUT PULSE WIDTH = 1.63µs

TEMIC BPV22NF

VCC = 3.3V

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc11

100µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 2400bps AT 10cm DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc09

100µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 2400bps AT 1cm DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc10

2µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 115.2kbps AT 10cm DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc08

2µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 115.2kbps AT 1cm DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

100

04020 60 80 100

RXD OUTPUT PULSE WIDTH

vs. DISTANCE

MAX3120 TOC06

DISTANCE (cm)

RXD PULSE WIDTH (µs)

TRANSMITTER POWER = 200mW/sr

INPUT PULSE WIDTH = 78µs

TEMIC BPV22NF

VCC = 3.3V

100

250

200

150

400

350

300

450

3.0 4.03.5 4.5 5.0 5.5

AMBIENT PHOTODIODE CURRENT REJECTION

vs. SUPPLY VOLTAGE

MAX3120 TOC05

SUPPLY VOLTAGE (V)

CURRENT REJECTION (µA)

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

_______________________________________________________________________________________

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc12

2µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 115.2kbps AT 1m DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3120 toc13

100µs/div

RXD

OUTPUT

INFRARED

INPUT

VCC = 3.3V, 2400bps AT 1m DISTANCE,

TERMIC BPV22NF, TRANSMIT POWER 200mW/sr

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

Pin Description

NAME FUNCTION

1 TXD IR Transmitter TTL/CMOS Data Input. High = LED on.

2 VCC Supply Voltage

3 GND Ground. Connect anode of PIN diode to GND. Connect GND to PGND.

4 PINC PIN Diode Cathode Input. Connect cathode of PIN diode to PINC.

8 RXD IR Receiver TTL/CMOS Data Output. Pulses low for IR input pulse.

7 LEDC LED Driver Output. Connect cathode of IR-emitting LED to LEDC.

6 PGND Power Ground. Ground for IR LED driver. Connect PGND to GND.

5SHDN Shutdown Input. Active low.

Detailed Description

The MAX3120 is an IrDA 1.2-compatible infrared (IR)

transceiver. By selecting appropriate external optical

components (see

IR LED and PIN Photodiode Selection

section), the MAX3120 will operate at data rates of

2.4kbps to 115kbps at distances from 1cm to 1m.

Because of its low-noise design, the MAX3120

achieves a bit error rate (BER) below 10-8 at maximum

data rates when used with the appropriate external

components. On-chip filtering rejects out-of-band

ambient light signals that would otherwise interfere with

IR communication. Also included in the MAX3120 is

a high-power LED driver capable of sinking 200mA. It

can drive most available IR LEDs at IrDA speeds of

2.4kbps to 115kbps.

Receiver

The MAX3120’s IR receiver amplifier reverse biases the

PIN diode by approximately 1.2V, and the PIN diode

converts pulses of IR light into pulses of current. The

input transimpedance (current-to-voltage) amplifier

then converts these current pulses into voltage pulses

of a useful magnitude. The MAX3120 filters the result-

ing output voltage pulses to remove low-frequency

ambient light interference and high-frequency circuit

noise. Finally, a high-speed comparator translates

these voltage pulses into usable CMOS output levels

(Figure 1).

MAX3120

Transmitter

The MAX3120’s IR transmitter consists of a high-power

MOS switch, capable of quickly switching 200mA with

less than 2Ωof on-resistance. Internal buffering keeps

the input capacitance of the TXD pin extremely low to

ease the input drive requirement. Connect an IR LED in

series with a current-setting resistor to select the appro-

priate IR output power (see the

Powering the IR LED

section). Note that the transmitter does not have an

automatic shutoff circuit, so pay special attention to com-

ponent power dissipation in high-duty-cycle transmit

schemes.

Applications Information

IR LED and PIN Photodiode Selection

The IrDA specification calls for an IR transmitter with a

peak wavelength between 850nm and 900nm. Within a

±15° half-cone-angle, the output intensity of the IR LED

must be between 40mW/sr and 500mW/sr. Outside a

±30° half-cone-angle, the output intensity of the IR LED

must fall below 40mW/sr. The optical rise and fall times

of the IR LED must be less than 600ns. Based on these

system requirements, the Hewlett Packard HSDL-4220

or the Temic TSHF5400 IR LEDs are two appropriate

choices.

Appropriate PIN photodiode selection is extremely

important to system performance. The PIN diode must

generate at least 200nA (minimum sensitivity of the

MAX3120) of current when aimed ±15° off-axis with an

incident irradiance of 4µW/cm2. Use the following equa-

tion to determine if the Temic BPV22NF meets these

requirements:

The first term (4µW/cm2) is the minimum guaranteed

irradiance in the ±15° angular range. The second term

(0.075cm2) is the effective sensitive area of the PIN

diode. The factor of 1.8 accounts for the efficiency

increase due to the spherical lens. The first 0.95 factor

normalizes the sensitivity to the 875nm wavelength,

while the second 0.95 factor adjusts for decreased

receiver efficiency at ±15° off-axis. The last term,

0.6A/W, is the sensitivity of the PIN diode. In this exam-

ple, the Temic BPV22NF is an appropriate selection.

The final important factor in selecting a PIN diode is

effective diode capacitance. It is important to keep this

capacitance below 70pF at 1.2V reverse bias. Higher

input capacitance can compromise system noise per-

formance by increasing the noise gain of the input tran-

simpedance amplifier.

Powering the IR LED

Set the current in the IR LED using an external resistor.

Consult the IR LED manufacturer’s data sheet to select

a forward current that will meet IrDA specifications dis-

cussed in the

IR LED and PIN Photodiode Selection

section. Look up the drop across the LED (VLED) and

the drop across the MAX3120 LED driver (see

Typical

Operating Characteristics

- VLEDC) and choose the cur-

rent-setting resistor based on the following equation:

Using the Hewlett Packard HSDL-4220 IR LED as an

example, VCC = 5V, ISET = 100mA, and VLED = 1.67V,

therefore: VLEDC = 0.08V

RSET = 32.5Ω

V-V -V

SET CC LED LEDC

SET

IPIN =

=(4 W/cm )(0.075cm )(1.8)(0.95) (0.6A/W)

291nA

22 2

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

6 _______________________________________________________________________________________

Figure 1. Functional Diagram

MAX3120

BIAS

BANDPASS

FILTER

SHDN VCC

RXD TXD LEDC

PGND

PINC

1.2V

GND

Power-dissipation requirements of the MAX3120, IR

LED, and RSET must be met based on maximum duty

cycle and output current requirements.

MAX3120 Power Dissipation = ISET ·VLEDC · Duty Cycle

IR LED Power Dissipation = ISET · VLED · Duty Cycle

RSET Power Dissipation = ISET2·RSET · Duty Cycle

Power-Supply Noise Rejection

Because of the extremely sensitive nature of photodi-

ode amplifiers, it is important to maintain a quiet supply

voltage. Use a separate analog supply voltage where

possible. Place a 1µF ceramic bypass capacitor as

close to the VCC pin as possible. In especially noisy

systems, connect a small (10Ω) resistor in series with

VCC, in addition to the normal bypass capacitor.

Layout Considerations

The MAX3120 requires careful layout techniques to mini-

mize parasitic signal coupling to the PINC input. Keep

the lead length between the photodiode and PINC as

short as possible. Be sure to keep PC board traces to

the PIN diode separate from other noisy traces. To mini-

mize coupling, run the AGND trace adjacent to the PINC

trace on both sides. To prevent oscillation, avoid routing

the RXD signal near the PINC signal. Connect the anode

of the PIN diode, the GND pin, and the supply bypass

capacitor pin in a star-ground connection. Connect

PGND and GND together. Reduce the output trace

length from RXD as much as possible to minimize cou-

pling back to the input via parasitic capacitance.

Chip Information

TRANSISTOR COUNT: 256

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

_______________________________________________________________________________________ 7

Package Information

MAX3120

Low-Profile, 3V, 120µA,

IrDA Infrared Transceiver

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600