MAXIM MAX3130, MAX3131 Technical data

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General Description

The MAX3130/MAX3131 combine an IrDA 1.2 compati­ble infrared transceiver with an RS-232 interface—all in
a single 3V-powered hybrid microcircuit. The infrared
transceiver supports IrDA data rates of 2.4kbps to
115kbps. The infrared receive channel provides a high­gain/low-noise PIN-diode amplifier with 100µA of ambi­ent photodiode current rejection at a +3V supply. A
high-power LED driver capable of sinking 200mA is
included in the infrared transmit path. The on-board
encoder/decoder (ENDEC) compresses/stretches sig­nals to and from the external UART, allowing IrDA com­munication even with non-IrDA UARTs.

A 2-driver/2-receiver RS-232 transceiver supports data
rates up to 120kbps. A proprietary, high-efficiency, dual
charge-pump power supply and a low-dropout trans­mitter combine to deliver true RS-232 performance from
a single +3.0V to +5.5V supply. Selectable shutdown
for IR and RS-232 circuitry reduces supply current to
1µA.

The MAX3130 is optimized for applications using a sin­gle UART for both infrared and RS-232 communication.
The infrared transmitter input and infrared receiver out­put are multiplexed with one RS-232 transmitter input
and one RS-232 receiver output, respectively. The
MAX3131’s IrDA transceiver and RS-232 transceivers
are separate and have their own data inputs and outputs.

Both these devices require a minimum of external com­ponents: four small 0.1µF capacitors, a photodiode, an
infrared LED, and a current-setting resistor.

Applications

Personal Digital Assistants (PDAs)
Palmtop Computers
Battery-Powered Systems
Hand-Held Equipment
Peripherals
IrDA Applications
Cellular Phones

Features

♦ Integrated RS-232 and IrDA in Single 28-Pin SSOP

Package

♦ 370µA Supply Current
♦ IrDA 1.2 Compatible: 2.4kbps to 115kbps

Data Rate

♦ On-Board IR Encoder/Decoder Allows Use of

Non-IrDA UARTs

♦ +3.0V to +5.5V Single-Supply Operation
♦ Meet EIA/TIA-232 Specifications Down to +3V
♦ 200mA, High-Current Infrared LED Drive
♦ 1µA Low-Power Shutdown with RS-232

Receivers Active

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

________________________________________________________________

Maxim Integrated Products

1

28
27
26
25
24
23
22
21
20
19
18
17
16
15

1
2
3
4
5
6
7
8

9
10
11
12
13
14

R2OUT
R2IN
T2OUT
RSSD
V­C2-

IRSD

C2+
C1­C1+
V+
N.C.
LEDC
PGND

PINC

AGND

AV

CC

N.C.

V

CC

GND

BAUD16

T1OUT

R1IN

R1OUT

IRMODE (TXD)

T2IN

T1IN

EDGEDET (RXD)

SSOP

TOP VIEW

MAX3130
MAX3131

( ) ARE FOR MAX3131

19-1402; Rev 0; 11/98

PART

MAX3130CAI

MAX3130EAI
MAX3131CAI

0°C to +70°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

28 SSOP
28 SSOP
28 SSOP

Pin Configuration

Ordering Information

MAX3131EAI -40°C to +85°C 28 SSOP

µA

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= AVCC= 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical

values are at T

A

= +25°C and VCC= AVCC= 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.

VCCto GND..............................................................-0.3V to +6V

AV

CC

to AGND.........................................................-0.3V to +6V

V

CC

to AVCC.......................................................................±0.3V

AGND, PGND to GND ........................................................±0.1V

V+ to GND................................................................-0.3V to +7V

V- to GND.................................................................+0.3V to -7V

V+ to V-................................................................................+13V

Inputs (referenced to GND)

T1IN, T2IN, TXD,

RSSD, IRMODE, BAUD16,

IRSD....................................................................-0.3V to +6V

R1IN, R2IN .....................................................................±25V

Outputs (referenced to GND)

T1OUT, T2OUT............................................................±13.2V

R1OUT, R2OUT, EDGEDET, RXD.........-0.3V to (V

CC

+ 0.3V)

LEDC...................................................................-0.3V to +6V

Output Short-Circuit Duration (to V

CC

or GND)

T1OUT, T2OUT.....................................................Continuous

Output Currents

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

LEDC 20% Duty Cycle t

ON

< 90µs..............................500mA

Input Current

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

Continuous Power Dissipation (T

A

= +70°C)

SSOP (derate 9.52mW/°C above +70°C)...................762mW

Operating Temperature Ranges

MAX3130/MAX3131CAI ....................................0°C to +70°C

MAX3130/MAX3131EAI..................................-40°C to +85°C

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

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

±0.01 ±1.0

2.4

120 200

Output Voltage Low I

SINK

= 1.6mA

0.25 1.0

0.1 0.4 V

Output Voltage High I

SOURCE

= 1.0mA

VCC-VCC-

0.6 0.05

V

2.0

0.8

1.0 10

0.01 1.0

MIN TYP MAX

Data Rate (Note 3)

µAVIN= 0 to V

CC

Input Leakage Current

2.4 115.2

VCC= AVCC= 5V

kbps

Equivalent Input Noise Current 10 nA

RMS

Input Current Sensitivity (Note 3) 0.0002 6 mA
Ambient Photodiode Current

Rejection

AVCC= 3.3V 100
AVCC= 5V 375

µA

V

VCC= AVCC= 3.3V

Input Logic Threshold High

VInput Logic Threshold Low

µATA= +25°C (Note 2)Analog Power-Supply Current

mAVCC= 3.3V or 5V, TA= +25°C (Note 2)Power-Supply Current

RSSD = low or IRMODE = low,
T

A

= +25°C (Note 2)

Shutdown Supply Current µA

µA

IRSD = low, TA= +25°C (Note 2)

Shutdown Analog Supply Current

UNITSCONDITIONSPARAMETER

LOGIC INPUTS (T1IN, T2IN, TXD, IRMODE, BAUD16, IRSD, RSSD)

DC CHARACTERISTICS

LOGIC OUTPUTS (R1OUT, R2OUT, RXD, EDGEDET)

IR RECEIVER

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= AVCC= 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical

values are at T

A

= +25°C and VCC= AVCC= 3.3V.)

Data rate = 2.4kbps
Data rate = 115kbps

AVCC= 3.3V

IR Receiver Disable Time Delay until I

AVCC

< 1µA 10 µs

IR Receiver Enable Time Delay until maximum IR receive data rate is valid 300 µs
IR Receiver Output Pulse Width

BAUD16 = static
(Note 3)

190

µs

AVCC= 5V

1 1.6 8

IR TRANSMITTER

Transmitter Rise Time 10% to 90% of 200mA drive current 20 600 ns
Transmitter Fall Time 90% to 10% of 200mA drive current 20 600 ns

Transmitter Output Resistance I

OUT

= 200mA

1.15 2

Ω

0.9 1.6

µs

Off-Leakage Current

1.43 2.23

V

LEDC

= 5.5V

t

PHL

t

PLH

0.01 10.0 µA

IrDA ENCODER/DECODER (ENDEC)

Maximum Operating Frequency Maximum frequency at BAUD16 2 MHz
IR Output Pulse Width f

BAUD16

= 1.8432MHz, measured at V

LEDC

BAUD16 Operating Frequency Range f

BAUD16

required to enable ENDEC 34.6 2000 kHz

RS-232 RECEIVER

Input Voltage Range -25 25 V
Input Threshold Low

VCC= 3.3V 0.6 1.2

V

VCC= 5V 0.8 1.5

Input Threshold High

VCC= 3.3V 1.5 2.4

V

VCC= 5V 1.8 2.4
Input Hysteresis 0.3 V
Input Resistance TA= +25°C 357kΩ

Receiver Propagation Delay

R_IN to R_OUT,

CL= 150pF

300

ns

300

Receiver Skew



t

PHL

- t

PLH

, C

L

= 150pF

300 ns

RS-232 TRANSMITTER OUTPUTS

Output Voltage Swing T1OUT, T2OUT, loaded with 3kΩ to GND ±5 ±5.4 V
Output Resistance VCC= V+ = V- = 0, T_OUT = ±2V 300 10M Ω
Output Short-Circuit Current V

T_OUT

= 0 ±35 ±60 mA

Output Leakage Current

V

T_OUT

= ±12V, VCC= 0 to 5.5V,

RS-232 transceiver shutdown

±25 µA

Maximum Data Rate RL= 3kΩ, CL = 1000pF, one transmitter switching 120 235 kbps
Transmitter Skew



t

PHL

- t

PLH

300 ns

PARAMETER CONDITIONS MIN TYP MAX UNITS

IR TRANSMITTER

IrDA ENCODER/DECODER (ENDEC)

RS-232 RECEIVER

RS-232 TRANSMITTER OUTPUTS

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= AVCC= 3.3V, GND = AGND = PGND, C1–C4 = 0.1µF, RL= 3kΩ, TA = +25°C, unless otherwise noted.)

200

240
220

300
280
260

360
340
320

380

-40 0 20-20 40 60 80 100

SUPPLY CURRENT vs. TEMPERATURE

MAX3130 toc01

TEMPERATURE (°C)

I

CC

(µA)

VCC = 3.3V or 5V

90

110

100

130

120

140

150

-40 20 40-20 0 60 80 100

ANALOG SUPPLY CURRENT

vs. TEMPERATURE

MAX3130 toc02

TEMPERATURE (°C)

I

AVCC

(µA)

AVCC = 5V

AVCC = 3.3V

0

100

300

200

400

500

3.0 4.03.5 4.5 5.0 5.5

AMBIENT PHOTODIODE CURRENT

REJECTION vs. SUPPLY VOLTAGE

MAX3130 toc03

SUPPLY VOLTAGE (V)

CURRENT REJECTION (µA)

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

-40 0-20 20 40 80 100

LED DRIVER ON-RESISTANCE

vs. TEMPERATURE

MAX3130 toc04

TEMPERATURE (°C)

R

LED

(Ω)

VCC = 3.3V

VCC = 5V

I

LEDC

= 200mA

0

200

100

400

300

500

600

100 200 250150 300 350 400

LEDC VOLTAGE vs. LEDC CURRENT

MAX3130 toc05

LEDC CURRENT (mA)

LEDC VOLTAGE (mV)

PULSED AT
20% DUTY CYCLE

VCC = 3.3V

VCC = 5V

0

20

60

40

80

100

04020 60 80 100

RXD OUTPUT PULSE WIDTH

vs. DISTANCE (2400bps)

MAX3130 toc06

DISTANCE (cm)

RXD PULSE WIDTH (µs)

TRANSMITTER POWER = 200mW/sr
INPUT PULSE WIDTH = 78µs
TEMIC BPV22NF
V

CC

= 3.3V

Note 1: C1–C4 = 0.1µF, tested at +3.3V ±10%. C1 = 0.047µF, C2–C4 = 0.33µF, tested at +5.0V ±10%.
Note 2: All supply current measurements are made under no-load condition on all outputs, and all input voltages are at V

CC

or GND.

Note 3: For a compliant IrDA input signal where the data rate is within the supported data rate for the IR receive mode: rise/fall

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

630

MIN TYP MAX

VCC= 3.3V, RL= 3kΩ to

7kΩ, measured from

+3V to -3V or -3V to +3V,

TA = +25°C

Transition-Region Slew Rate V/µs

UNITSCONDITIONSPARAMETER

100Delay until transmitter outputs are validTransmitter Enable Time µs

CL= 150pF to 1000pF

CL= 150pF to 2500pF 430

ELECTRICAL CHARACTERISTICS (continued)

(VCC= AVCC= 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical

values are at T

A

= +25°C and VCC= AVCC= 3.3V.)

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

_______________________________________________________________________________________

5

1.0

2.0

1.5

3.0

2.5

3.5

4.0

04020 60 80 100

RXD OUTPUT PULSE WIDTH vs. DISTANCE

(115.2 kbps)

MAX3130 toc07

DISTANCE (cm)

RXD PULSE WIDTH (µs)

TRANSMITTER POWER = 200mW/sr
INPUT PULSE WIDTH = 1.63µs
TEMIC BPV22NF
V

CC

= 3.3V

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3130 toc08

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

2000 30001000 4000 5000

V

OUT

+

1 TRANSMITTER AT 235kbps
1 TRANSMITTER AT 15kbps

V

OUT

-

0

4
2

8
6

10

12

16
14

18

0 1000 2000 3000 4000 5000

RS-232 TRANSMITTER SLEW RATE

vs. LOAD CAPACITANCE

MAX3130 toc09

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

-SLEW

+SLEW

0

5

10

15

20

25

30

35

40

0

SUPPLY CURRENT vs. LOAD CAPACITANCE

(RS-232 TRANSMITTING)

MAX3130-toc10

LOAD CAPACITANCE (pF)

I

CC

(mA)

2000 30001000 4000 5000

235kbps

1 TRANSMITTER DRIVEN ONLY

120kbps

20kbps

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc11

2µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 115.2kbps AT 1cm DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc12

100µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 2400bps AT 1cm DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

Typical Operating Characteristics (continued)

(VCC= AVCC= 3.3V, GND = AGND = PGND, C1–C4 = 0.1µF, RL= 3kΩ, TA = +25°C, unless otherwise noted.)

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

6 _______________________________________________________________________________________

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc15

2µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 115.2kbps AT 1m DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc16

100µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 2400bps AT 1m DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

Pin Description

Typical Operating Characteristics (continued)

(VCC= AVCC= 3.3V, GND = AGND = PGND, C1–C4 = 0.1µF, RL= 3kΩ, TA = +25°C, unless otherwise noted.)

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc13

2µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 115.2kbps AT 10cm DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

2V/div

2V/div

RXD OUTPUT

vs. INFRARED INPUT

MAX3130 toc14

100µs/div

RXD
OUTPUT

INFRARED
INPUT

V

CC

= 3.3V, 2400bps AT 10cm DISTANCE
TEMIC BPV22NF
TRANSMIT POWER 200mW/sr

MAX3131MAX3130

PIN

1 IR Receiver TTL/CMOS Data OutputRXD—

—

Edge Detector Output. EDGEDET goes low if activity is sensed on either the RS-232
receiver or the IrDA receiver, depending on the state of IRMODE. See

EDGEDET: Edge-

Detection Circuitry

section.

EDGEDET

1

2 TTL/CMOS RS-232 Transmitter InputT1IN2

FUNCTIONNAME

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

_______________________________________________________________________________________ 7

Pin Description (continued)

TTL/CMOS RS-232 Receiver Output. For the MAX3130, drive IRMODE low to connect
R2OUT to the IR receiver output, and drive IRMODE high to connect R2OUT to the
RS-232 receiver output. For the MAX3131, R2OUT is always internally connected to the
RS-232 receiver output.

R2OUT2828

RS-232 Receiver InputR2IN2727

RS-232 Transmitter OutputT2OUT2626

Shutdown Input for the RS-232 Transmitters and Charge Pump

RSSD

2525

-5.5V Generated by the Internal Charge PumpV-2424

Negative Terminal of the Inverting Charge-Pump CapacitorC2-2323

Positive Terminal of the Inverting Charge-Pump CapacitorC2+2222

Negative Terminal of the Voltage-Doubling Charge-Pump CapacitorC1-2121

Positive Terminal of the Voltage-Doubling Charge-Pump CapacitorC1+2020

Shutdown Input for the IrDA Transceiver Circuitry

IRSD

1515

Analog Ground for IR Signal Processing. Connect to GND.AGND1313

Analog Supply Voltage VCCfor IR Signal Processing. AVCCrange is 3.0V to 5.5V.AV

CC

1212

Silicon PIN Photodiode Input. Connect PINC to the cathode of the PIN photodiode.
Connect the anode of the PIN photodiode to GND.

PINC1414

Open-Drain Output for Driving the IR LED. Connect LEDC to the cathode of the IR LED.LEDC1717

Power Ground for IR LED Driver. Connect to GND.PGND1616

+5.5V Generated by the Internal Charge PumpV+1919

No Connection. Do not make connections to these pins.

N.C.11, 1811, 18

6
7

8
9

10

MAX3131

3

4
5

MAX3130

PIN

RS-232 Receiver InputR1IN6
RS-232 Transmitter OutputT1OUT7

16-Times Baud-Rate Input. To use the ENDEC, apply a signal that is 16 times the baud
rate into BAUD16. Connect BAUD16 to GND or VCCto disable the ENDEC.

BAUD168

GroundGND9

3.0V to 5.5V Supply VoltageV

CC

10

TTL/CMOS RS-232 Transmitter Input. For the MAX3130, drive IRMODE low to connect
T2IN to the IR transmitter input, and drive IRMODE high to connect T2IN to the RS-232
transmitter input. For the MAX3131, T2IN is always connected to the RS-232 transmitter
input.

T2IN3

IR Transmitter TTL/CMOS Data InputTXD—
TTL/CMOS RS-232 Receiver OutputR1OUT5

FUNCTIONNAME

—

IR Mode Control. Drive IRMODE low to connect R2OUT to the IR receiver output and
T2IN to the IR transmitter input. Driving IRMODE low also shuts down the RS-232
charge pump and puts the RS-232 transmitter outputs in a high-impedance state. Drive
IRMODE high to connect R2OUT to the RS-232 receiver output and connect T2IN to the
RS-232 transmitter input.

IRMODE

4

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

8 _______________________________________________________________________________________

Detailed Description

The MAX3130/MAX3131 are IrDA 1.2 compatible,
infrared transceivers with an integrated RS-232 inter­face. By selecting appropriate external optical compo­nents, these devices support IrDA 1.2 data rates from

2.4kbps to 115kbps at distances from 1cm to 1m. A
low-noise design allows them to achieve a bit-error rate
below 10-8at maximum data rates. On-chip filtering
rejects out-of-band ambient light signals that interfere
with infrared communication. Both devices include a
high-power LED driver capable of sinking 200mA.

The MAX3130 and MAX3131 contain two RS-232 drivers
and two RS-232 receivers that support data rates up to
120kbps. The RS-232 transceiver is powered by a high­efficiency, dual charge-pump power supply that oper­ates with input supply voltages from +3.0V to +5.5V.

The MAX3130 is optimized for applications using a sin­gle UART for both infrared and RS-232 communication.
The infrared transmitter input and infrared receiver out­put are multiplexed with one RS-232 transmitter input
and one RS-232 receiver output, respectively. The
MAX3131 IrDA and RS-232 transceivers are indepen­dent of each other for use in simultaneous multiprotocol
transceiver applications.

IR Receivers

The receiver amplifier reverse biases the PIN diode
with approximately 1.2V, and the PIN diode converts
pulses of IR light into pulses of current. The input trans­impedance (current-to-voltage) amplifier converts and
amplifies these current pulses into voltage pulses. The
MAX3130/MAX3131 incorporate filters that remove low­frequency ambient light interference and high-frequency
circuit noise from these voltage pulses. A high-speed
comparator then translates these voltage pulses into
CMOS output levels. Figures 1 and 2 show system
functional diagrams.

The RXD pin is the output of the infrared receiver for
the MAX3131. The R2OUT pin is the output of the
infrared receiver for the MAX3130 (IRMODE = low).
With the ENDEC disabled, the infrared receiver output
pulses low upon each incoming infrared pulse. The
pulse width of the receiver output depends on many
factors, including transmitter distance and power, PIN
photodiode efficiency and area, and incoming data
rate. Under all circumstances the output pulse is less
than one baud period. To communicate with UARTs
that are not IrDA compatible, enable the ENDEC (see
the

IrDA Encoder/Decoder (ENDEC)

section).

MAX3131 Operational Modes Table

RSSD IRSD

T_OUT R_IN LEDC RXD

0 0 High-Z Enabled Enabled Logic High
0 1 High-Z Enabled Enabled IrDA Output
1 0 Enabled Enabled Enabled Logic High
1 1 Enabled Enabled Enabled IrDA Output

MAX3130 Function Table

RSSD

X

X 0

0

IRMODE

MAX3130

CONTROL INPUTS

IRSD

0

1

RS-232

Input

RS-232

Input

T1IN

LOGIC INPUTS

IrDA

Input

IrDA

Input

T2IN

EnabledHigh-Z

High-Z

T1OUT

RS-232 I/O

High-Z

High-Z

T2OUT

Disabled

RS-232

Input

RS-232

Input

R1IN PINC

RS-232

Input

RS-232

Input

R2IN

IrDA

INPUT

RS-232

Output

RS-232

Output

R1OUT

LOGIC OUTPUTS

IrDA

Output

IrDA

Output

R2OUT

Disabled

Enabled

Enabled

LEDC

IrDA

OUTPUT

0 1 0

RS-232

Input

RS-232

Input

High-Z High-Z

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

Disabled

0 1 1

RS-232

Input

RS-232

Input

High-Z High-Z

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

Disabled Enabled

Disabled

Enabled

1 1 0

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

Disabled

1 1 1

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

RS-232

Input

RS-232

Input

RS-232

Output

RS-232

Output

Disabled

X = Don’t care

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

_______________________________________________________________________________________ 9

MAX3130

EDGE

EDGE

Rx
RxIN

TxIN

Tx

ENDEC

CHARGE PUMP

SHDN

1µF

R

SET

GND

V

CC

1µF

AGND

AV

CC

EDGEDET

T2OUT

R2IN

R1IN

RSSD

V+
V-

LEDC

PGND

PINC

1.2V

C4

C3

T1OUT

RS-232
INPUTS

RS-232
OUTPUTS

OFF

ON

IR

232

OFF

ON

RECEIVE

LOGIC

OUTPUTS

TRANSMIT

LOGIC

INPUTS

C1+

C1

C1-

C2+

C2

C2-

IRSD

BIAS

5k

5k

BAUD16

IRMODE

R1OUT

R2OUT

T1IN

T2IN

f

BAUD16

Figure 1. MAX3130 Functional Diagram

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

10 ______________________________________________________________________________________

MAX3131

Rx
RxIN

TxIN

Tx

ENDEC

CHARGE PUMP

1µF

R

SET

GND

V

CC

1µF

AGND

AV

CC

PINC

PGND

LEDC

R2IN

R1IN

V-

C4

C3

T1OUT

T2OUT

RS-232
INPUTS

RS-232
OUTPUTS

OFF

ON

OFF

ON

RS-232

RECEIVE

LOGIC

OUTPUTS

IrDA RECEIVE

LOGIC

OUTPUT

RS-232

TRANSMIT

LOGIC

INPUTS

IrDA TRANSMIT

LOGIC INPUT

C1+

C1

C2

C1-

C2+

C2-

IRSD

BIAS

5k

5k

BAUD16

R1OUT

R2OUT

T1IN

T2IN

TXD

RXD

f

BAUD16

V+

RSSD

SHDN

1.2V

Figure 2. MAX3131 Functional Diagram

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

______________________________________________________________________________________ 11

IR Transmitter

The infrared transmitter consists of an internal high­power, open-drain MOSFET switch. This switch has an
on-resistance of less than 2Ω and is capable of switch­ing 200mA of current. Internal buffering keeps the input
capacitance of the TXD pin extremely low to ease user
drive requirements. Connect an IR LED in series with a
current-setting resistor to select the appropriate IR out­put power (see the

Powering the IR LED

section). The
transmitter is not current limited so do not exceed the
power dissipation of the external components during
high duty-cycle transmit schemes.

The TXD input controls the IR LED for the MAX3131.
The T2IN input controls the IR LED for the MAX3130
(IRMODE = low). With the ENDEC disabled (see

IrDA

Encoder/Decoder (ENDEC)

section), the IR LED is
turned on by a logic-high signal at the TXD or T2IN
input, for the MAX3131 and MAX3130 respectively.

IRMODE

: Multiplexed RS-232 Operation

and IrDA Operation (MAX3130)

The MAX3130 has the capability to multiplex R2OUT and
T2IN between the IrDA infrared interface and the RS-232
electrical interface. The state of the IRMODE input deter­mines which interface (infrared or RS-232) is multiplexed
to R2OUT and T2IN. When IRMODE is low, R2OUT acts
as the infrared receiver output and T2IN acts as the
infrared transmitter input. Also, while IRMODE is low, the
RS-232 charge pumps are shut down and the RS-232
transmitters are disabled (see

Shutdown

section). When
IRMODE is high, R2OUT and T2IN assume their func­tions as the RS-232 data receive output and transmit
input, respectively. Also, while IRMODE is high, the IR
transmitter is disabled (turned off).

EDGEDET

: Edge-Detection Circuitry

(MAX3130)

The MAX3130 has internal edge-detection circuitry that
monitors the RS-232 R2OUT line when IRMODE is low
and monitors the IrDA receive channel when IRMODE
is high. EDGEDET goes low when a positive or negative
edge is detected on either the RS-232 R2OUT line or
the IrDA receive channel (depending on the IRMODE
pin). This edge-detection feature is useful for initiating
an interrupt when data is received on the deselected
line. The EDGEDET signal is cleared when IRMODE is
toggled. Table 1 shows EDGEDET operation.

IrDA Encoder/Decoder (ENDEC)

The MAX3130 and MAX3131 provide an on-board
ENDEC to communicate with UARTs that are not IrDA
compatible. The ENDEC is enabled by applying a clock
with a frequency 16 times the baud rate to the BAUD16
input. This BAUD16 clock is commonly provided on
UARTs that do not have IrDA ENDEC capability. Figure
3 illustrates the operation of the ENDEC. The ENDEC
stretches the incoming infrared pulse (a pulse between

IRSD RSSD IRMODE

R2IN IrDA RxIN

EDGEDET*

X X 0 X
X X 0 X
X X 1 X
X X 1 X

Table 1. EDGEDET Operation

1.41µs < t < 3CS

16CS 32CS

16CS

R2OUT (RXD)

WITH ENDEC ENABLED

R2OUT (RXD)

WITH ENDEC DISABLED

CS = BAUD16 CLOCK CYCLES
* HIGH = INFRARED LIGHT PULSE
( ) ARE FOR MAX3131

INFRARED

PHOTODIODE INPUT *

Figure 3a. ENDEC Operation, Receiving Infrared

X

= Don’t care

*

EDGEDET is cleared by any transition on IRMODE.

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

12 ______________________________________________________________________________________

3CS

7CS

16CS

T2IN (TXD)

CS = BAUD16 CLOCK CYCLES
* HIGH = INFRARED LIGHT PULSE
( ) ARE FOR MAX3131

INFRARED LED

OUTPUT *

Figure 3b. ENDEC Operation, Transmitting Infrared

LapLink is a trademark of Traveling Software.

1µs and three BAUD16 clock cycles) into a full baud
period (Figure 3a). Signals applied to TXD are inverted
and compressed to three BAUD16 clock cycles by the
ENDEC before being transmitted (Figure 3b). The
ENDEC is disabled by connecting the BAUD16 input to
VCCor GND.

Dual Charge-Pump Voltage Converter

The MAX3130/MAX3131’s internal power supply con­sists of a regulated dual charge pump that provides
output voltages of +5.5V (doubling charge pump) and

-5.5V (inverting charge pump) for supply voltages from
+3.0V to +5.5V. The charge pump operates in a dis­continuous mode: if the output voltages are less than

5.5V, the charge pumps are enabled; if the output volt­ages exceed 5.5V, the charge pumps stop switching.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies (Figures 1 and 2). If RSSD (or IRMODE
for MAX3130) is low, both charge pumps shut down.

RS-232 Transmitters

The RS-232 transmitters are inverting level translators
that convert CMOS-logic levels to ±5.0V EIA/TIA-232
levels. The MAX3130/MAX3131 transmitters are guar­anteed for data rates of 120kbps, providing compatibili­ty with PC-to-PC communication software, such as
LapLink™. These RS-232 transmitters typically operate
at data rates of 235kbps. The RS-232 transmitter out­puts are high impedance when either IRMODE or RSSD
are low.

The MAX3130/MAX3131 RS-232 receivers translate RS­232 signal levels to CMOS-level logic. The RS-232
receivers also perform a logic inversion from input to
output. The receivers are always active and are not
affected by the RS-232 shutdown input (RSSD).

__________ Applications Information

Shutdown

The MAX3130/MAX3131 have split analog and digital
supplies (VCCand AVCC) with separate shutdown
modes. When IRSD is pulled low, the IR receiver is dis­abled and AVCCcurrent reduces to <1µA. When RSSD
or IRMODE is pulled low, the RS-232 charge pumps
are disabled and the RS-232 transmitter outputs
become high impedance. In this mode, the VCCcurrent
reduces to <10µA.

IR LED 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. Within these cases, the opti­cal rise and fall times of the IR LED must be less than
600ns. Based on these system requirements the HP
HSDL-4220, the Temic TSHF5400, or equivalent IR
LEDs are appropriate choices.

Powering the IR LED

Set the current in the IR LED with an external resistor.
Using the IR LED manufacturer’s data sheet, select a
forward current that meets the IrDA specifications dis­cussed in the

IR LED Selection

section. Determine the

forward bias voltage of the IR LED (V

IRLED

) and the
voltage drop across the MAX3130/MAX3131 LED driver
(see LEDC Voltage vs. LEDC Current graph in the

Typical Operating Characteristics

) and choose the cur-

rent-setting resistor based on the following equation:

R

SET

= (VCC- V

IRLED

- V

LEDC

) / I

SET

Using the HP HSDL-4220 IR LED as an example:

VCC= 5V, I

SET

= 100mA, V

IRLED

= 1.67V

V

LEDC

= 90mV

R

SET

= (5V - 1.67V - 90mV) / 0.1A = 32.4Ω

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

______________________________________________________________________________________ 13

Power dissipation of the MAX3130/MAX3131, IR LED,
and R

SET

are based on the maximum LED current and

duty cycle.
Use the following equations to calculate the power dis-

sipation in each component:

MAX3130 power dissipation = I

SET

· V

DRV

· duty cycle

IR LED power dissipation = I

SET

· V

IRLED

· duty cycle

R

SET

power dissipation = I

SET

2

· R

SET

· duty cycle

For reliable operation, do not exceed maximum power
dissipation of the components.

PIN Photodiode Selection

PIN photodiode selection is extremely important to sys­tem performance. The PIN diode must generate at least
200nA (minimum sensitivity of the MAX3130/MAX3131)
of current when aimed ±15° off-axis with an incident
irradiance of 4µW/cm2. The following equation deter­mines if the Temic BPV22NF meets these requirements:

I

PIN

= (4µW/cm2) (0.075cm2) (0.95) (0.95) (1.8) (0.6A/W)
= 292nA

The first term (4mW/cm2) is the minimum guaranteed
irradiance in the ±15° angular range. The second term
(0.075cm2) is the sensitive area of the PIN diode. The
first 0.95 factor normalizes the sensitivity to the 875nm
wavelength and the second 0.95 factor adjusts for the
decreased receiver efficiency at ±15° off-axis. The 1.8
factor accounts for the round lens which increases the
effective PIN diode area. The last term (0.6A/W) is the
sensitivity of the PIN diode. Based on this example, the
Temic BPV22NF is an appropriate selection.

The final important factor in selecting a PIN diode is the
effective diode capacitance. It is important to keep this
capacitance below 70pF at 1.2V reverse bias. Higher
input capacitance compromises the noise performance
of the system by increasing the noise gain of the input
transimpedance amplifier.

Capacitor Selection

The capacitor type used for C1–C4 is not critical for
proper operation; either polarized or nonpolarized
capacitors are good choices. The charge pump
requires 0.1µF capacitors for 3.3V operation. For other
supply voltages, refer to Table 2 for suggested capaci­tor values. Do not use values smaller than those listed
in Table 2. Increasing the capacitor values (e.g., by a
factor of 2) reduces ripple on the transmitter outputs
and slightly reduces power consumption. C2, C3, and
C4 can be increased without changing C1’s value.

However, do not increase C1 without also increas­ing the values of C2, C3, and C4.

When using the minimum required capacitor values,
make sure the capacitor value does not degrade
excessively with temperature. If in doubt, use capaci­tors with a larger nominal value. The capacitor’s equiv­alent series resistance (ESR) usually rises at low
temperatures and increases the amount of ripple on V+
and V-.

Power-Supply Noise Rejection

Because of the extremely sensitive nature of photodi­ode amplifiers, it is important to maintain a low-noise
supply voltage. Use a separate analog supply voltage
where possible. Place a 1µF ceramic bypass capacitor
as close as possible to the AVCCand VCCpins. In
especially noisy systems, connect a small (10Ω) resis­tor in series with VCC, in addition to the normal bypass
capacitors.

IrDA or RS-232 Application Circuit

Figure 4 shows how the MAX3130 is used to multiplex
between RS-232 and IrDA communication while using
only one UART. By using the IRMODE input, the type of
communication (infrared or RS-232) is controlled by the
I/O of a µP. The internal MAX3130 ENDEC is used to
translate between UART-type and IrDA-type bit­streams. If the UART has this capability, connect
BAUD16 of the MAX3130 to GND.

Figure 5 shows the MAX3131 used with two UARTs to
perform simultaneous IrDA and RS-232 communication.
UART1 is a software UART used to perform infrared
IrDA communication. The internal ENDEC on the
MAX3131 translates between UART-type and IrDA-type
bit-streams. The MAX3100 is implemented as UART2
and communicates via the RS-232 interface. The
MAX3100 interfaces to the µP using a SPI interface.

Layout Considerations

The MAX3130/MAX3131 require careful layout tech­niques to minimize parasitic signals coupling to the
PINC input. Keep the lead length between the photodi­ode and PINC as short as possible. Keep PC board
traces to the PIN diode away from other noisy traces.
To minimize coupling, run the AGND trace adjacent to
the PINC trace on both sides. To prevent oscillation,
avoid routing the RXD trace near the PINC trace.
Connect the anode of the PIN diode, GND, and the
ground lead of the AVCCbypass capacitor in a star­connection. Keep the output pins RXD and TXD as
short as possible to minimize coupling back to the input
via parasitic capacitance.

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

14 ______________________________________________________________________________________

RTS
CTS

Tx

Rx

T1IN
R1OUT

T2IN
R2OUT

TXD
RXD
BAUD16

T1OUT

R1IN

T2OUT

R2IN

LEDC

PINC

MAX3131

MAX3100

UART2

µP

IrDA

RS-232

1 2 3 4 5

6 7 8 9

DB-9

NON-IrDA UART

(UART1)

TX
RX

BAUD16

SPI

DIN
DOUT
SCLK
CS

Figure 5. Using the MAX3131 and Two UARTs to Perform Simultaneous IrDA and RS-232 Communication

Table 2. Required Capacitor Values

STANDARD

NON-IrDA

UART

RTS

CTS

Tx
Rx

BAUD16

T1IN
R1OUT

T2IN
R2OUT

BAUD16

T1OUT

R1IN

T2OUT

R2IN

LEDC

PINC

MAX3130

IRMODE

µP

I/O

232

IrDA

IrDA

RS-232

1 2 3 4 5

6 7 8 9

DB-9

Figure 4. Using the MAX3130 and a Single UART to Perform Both IrDA and RS-232 Communication

VCC(V) C1 (µF) C2, C3, C4 (µF)

3.0 to 3.6 0.1 0.1

4.5 to 5.5 0.047 0.33

3.0 to 5.5 0.1 0.47

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with

Integrated RS-232 Interface

______________________________________________________________________________________ 15

SSOP.EPS

________________________________________________________Package Information

Chip Information

TRANSISTOR COUNT: 1039

MAX3130/MAX3131

3V to 5.5V, IrDA Infrared Transceiver with
Integrated RS-232 Interface

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.

16

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

© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

NOTES