19-1402; Rev 0; 11/98 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface Features 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. ♦ 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 Ordering Information TEMP. RANGE PART 0°C to +70°C 28 SSOP MAX3130EAI MAX3131CAI MAX3131EAI -40°C to +85°C 0°C to +70°C -40°C to +85°C 28 SSOP 28 SSOP 28 SSOP Pin Configuration TOP VIEW 28 R2OUT EDGEDET (RXD) 1 Applications Personal Digital Assistants (PDAs) Palmtop Computers Battery-Powered Systems Hand-Held Equipment Peripherals IrDA Applications Cellular Phones PIN-PACKAGE MAX3130CAI T1IN 2 27 R2IN T2IN 3 26 T2OUT 25 RSSD IRMODE (TXD) 4 24 V- R1OUT 5 R1IN 6 MAX3130 MAX3131 23 C2- T1OUT 7 22 C2+ BAUD16 8 21 C1- GND 9 20 C1+ VCC 10 19 V+ N.C. 11 18 N.C. AVCC 12 17 LEDC AGND 13 16 PGND PINC 14 15 IRSD ( ) ARE FOR MAX3131 SSOP ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX3130/MAX3131 General Description MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface ABSOLUTE MAXIMUM RATINGS VCC to GND ..............................................................-0.3V to +6V AVCC to AGND .........................................................-0.3V to +6V VCC 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 (VCC + 0.3V) LEDC...................................................................-0.3V to +6V Output Short-Circuit Duration (to VCC or GND) T1OUT, T2OUT .....................................................Continuous Output Currents LEDC Continuous ........................................................200mA LEDC 20% Duty Cycle tON < 90µs..............................500mA Input Current PINC ..............................................................................10mA Continuous Power Dissipation (TA = +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 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. ELECTRICAL CHARACTERISTICS (VCC = AVCC = 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C and VCC = AVCC = 3.3V.) PARAMETER CONDITIONS MIN TYP MAX UNITS DC CHARACTERISTICS Power-Supply Current VCC = 3.3V or 5V, TA = +25°C (Note 2) 0.25 1.0 mA Analog Power-Supply Current TA = +25°C (Note 2) 120 200 µA Shutdown Supply Current RSSD = low or IRMODE = low, TA = +25°C (Note 2) 1.0 10 µA Shutdown Analog Supply Current IRSD = low, TA = +25°C (Note 2) 0.01 1.0 µA 0.8 V LOGIC INPUTS (T1IN, T2IN, TXD, IRMODE, BAUD16, IRSD, RSSD) Input Logic Threshold Low Input Logic Threshold High Input Leakage Current VCC = AVCC = 3.3V 2.0 VCC = AVCC = 5V 2.4 VIN = 0 to VCC V ±0.01 ±1.0 µA 0.1 0.4 V LOGIC OUTPUTS (R1OUT, R2OUT, RXD, EDGEDET) Output Voltage Low ISINK = 1.6mA Output Voltage High ISOURCE = 1.0mA VCC 0.6 VCC 0.05 V IR RECEIVER Data Rate (Note 3) 2.4 Input Current Sensitivity (Note 3) 0.0002 Ambient Photodiode Current Rejection AVCC = 3.3V 100 AVCC = 5V 375 Equivalent Input Noise Current 2 115.2 10 nARMS 6 _______________________________________________________________________________________ kbps mA µA µA 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface (VCC = AVCC = 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C and VCC = AVCC = 3.3V.) PARAMETER CONDITIONS MIN TYP MAX UNITS IR Receiver Disable Time Delay until IAVCC < 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) Data rate = 2.4kbps 1 Data rate = 115kbps 1 90 µs 1.6 8 20 600 ns IR TRANSMITTER Transmitter Rise Time 10% to 90% of 200mA drive current Transmitter Fall Time 90% to 10% of 200mA drive current Transmitter Output Resistance IOUT = 200mA Off-Leakage Current VLEDC = 5.5V 20 600 ns AVCC = 3.3V 1.15 2 AVCC = 5V 0.9 1.6 Ω 0.01 10.0 µA 2 MHz IrDA ENCODER/DECODER (ENDEC) Maximum Operating Frequency Maximum frequency at BAUD16 IR Output Pulse Width fBAUD16 = 1.8432MHz, measured at VLEDC 1.43 2.23 µs BAUD16 Operating Frequency Range fBAUD16 required to enable ENDEC 34.6 2000 kHz 25 V RS-232 RECEIVER Input Voltage Range Input Threshold Low Input Threshold High -25 VCC = 3.3V 0.6 1.2 VCC = 5V 0.8 1.5 V VCC = 3.3V 1.5 2.4 VCC = 5V 1.8 2.4 Input Hysteresis 0.3 Input Resistance TA = +25°C Receiver Propagation Delay R_IN to R_OUT, CL = 150pF Receiver Skew tPHL - tPLH, CL = 150pF 3 5 tPHL 300 tPLH 300 V V 7 kΩ ns 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 VT_OUT = 0 Output Leakage Current VT_OUT = ±12V, VCC = 0 to 5.5V, RS-232 transceiver shutdown Maximum Data Rate RL = 3kΩ, CL = 1000pF, one transmitter switching Transmitter Skew tPHL - tPLH ±35 120 ±60 mA ±25 µA 235 kbps 300 ns _______________________________________________________________________________________ 3 MAX3130/MAX3131 ELECTRICAL CHARACTERISTICS (continued) ELECTRICAL CHARACTERISTICS (continued) (VCC = AVCC = 3.0V to 5.5V, GND = AGND = PGND, C1–C4 = 0.1µF (Note 1), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C and VCC = AVCC = 3.3V.) PARAMETER CONDITIONS VCC = 3.3V, RL = 3kΩ to 7kΩ, measured from +3V to -3V or -3V to +3V, TA = +25°C Transition-Region Slew Rate Transmitter Enable Time MIN TYP MAX CL = 150pF to 1000pF 6 30 CL = 150pF to 2500pF 4 30 UNITS V/µs Delay until transmitter outputs are valid 100 µs 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 VCC 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. Typical Operating Characteristics (VCC = AVCC = 3.3V, GND = AGND = PGND, C1–C4 = 0.1µF, RL = 3kΩ, TA = +25°C, unless otherwise noted.) ANALOG SUPPLY CURRENT vs. TEMPERATURE 340 140 VCC = 3.3V or 5V IAVCC (µA) ICC (µA) AVCC = 5V 130 320 300 280 120 AVCC = 3.3V 110 260 240 500 CURRENT REJECTION (µA) 360 MAX3130 toc02 150 MAX3130 toc01 380 AMBIENT PHOTODIODE CURRENT REJECTION vs. SUPPLY VOLTAGE MAX3130 toc03 SUPPLY CURRENT vs. TEMPERATURE 400 300 200 100 100 220 90 -20 0 20 40 60 80 0 -40 100 -20 LED DRIVER ON-RESISTANCE vs. TEMPERATURE 40 60 80 100 1.0 VCC = 5V 0.6 VCC = 3.3V 400 300 200 VCC = 5V 0.4 0 0 20 40 TEMPERATURE (°C) 4 80 100 5.0 5.5 100 TRANSMITTER POWER = 200mW/sr INPUT PULSE WIDTH = 78µs TEMIC BPV22NF VCC = 3.3V 80 60 40 PULSED AT 20% DUTY CYCLE ILEDC = 200mA 0 4.5 20 100 0.2 4.0 RXD OUTPUT PULSE WIDTH vs. DISTANCE (2400bps) MAX3130 toc05 500 LEDC VOLTAGE (mV) 1.2 -20 3.5 SUPPLY VOLTAGE (V) 600 MAX3130 toc04 VCC = 3.3V -40 3.0 LEDC VOLTAGE vs. LEDC CURRENT 1.6 0.8 20 TEMPERATURE (°C) TEMPERATURE (°C) 1.4 0 RXD PULSE WIDTH (µs) -40 MAX3130 toc06 200 RLED (Ω) MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface 0 100 150 200 250 300 LEDC CURRENT (mA) 350 400 0 20 40 60 DISTANCE (cm) _______________________________________________________________________________________ 80 100 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface RXD OUTPUT PULSE WIDTH vs. DISTANCE (115.2 kbps) 3.0 2.5 2.0 1.5 1 TRANSMITTER AT 235kbps 1 TRANSMITTER AT 15kbps 2 1 0 -1 -2 -3 -4 VOUT- -5 1.0 0 20 40 60 80 -6 100 0 1000 DISTANCE (cm) 4000 40 MAX3130 toc09 18 1 TRANSMITTER DRIVEN ONLY 35 5000 235kbps 30 -SLEW 12 ICC (mA) SLEW RATE (V/µs) 3000 SUPPLY CURRENT vs. LOAD CAPACITANCE (RS-232 TRANSMITTING) 16 10 +SLEW 8 2000 LOAD CAPACITANCE (pF) RS-232 TRANSMITTER SLEW RATE vs. LOAD CAPACITANCE 14 MAX3130 toc08 VOUT+ 4 3 MAX3130-toc10 RXD PULSE WIDTH (µs) 3.5 6 5 TRANSMITTER OUTPUT VOLTAGE (V) TRANSMITTER POWER = 200mW/sr INPUT PULSE WIDTH = 1.63µs TEMIC BPV22NF VCC = 3.3V MAX3130 toc07 4.0 TRANSMITTER OUTPUT VOLTAGE vs. LOAD CAPACITANCE 25 120kbps 20 15 6 20kbps 4 10 2 5 0 0 0 1000 2000 3000 4000 5000 0 LOAD CAPACITANCE (pF) RXD OUTPUT vs. INFRARED INPUT 2000 3000 RXD OUTPUT vs. INFRARED INPUT MAX3130 toc11 2V/div 5000 MAX3130 toc12 RXD OUTPUT INFRARED INPUT INFRARED INPUT 2V/div 4000 LOAD CAPACITANCE (pF) RXD OUTPUT 2V/div 1000 2V/div 2µs/div VCC = 3.3V, 115.2kbps AT 1cm DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr 100µs/div VCC = 3.3V, 2400bps AT 1cm DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr _______________________________________________________________________________________ 5 MAX3130/MAX3131 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 Typical Operating Characteristics (continued) (VCC = AVCC = 3.3V, GND = AGND = PGND, C1–C4 = 0.1µF, RL = 3kΩ, TA = +25°C, unless otherwise noted.) RXD OUTPUT vs. INFRARED INPUT RXD OUTPUT vs. INFRARED INPUT MAX3130 toc13 2V/div RXD OUTPUT 2V/div INFRARED INPUT 2V/div RXD OUTPUT 2V/div INFRARED INPUT 100µs/div VCC = 3.3V, 2400bps AT 10cm DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr 2µs/div VCC = 3.3V, 115.2kbps AT 10cm DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr RXD OUTPUT vs. INFRARED INPUT MAX3130 toc14 RXD OUTPUT vs. INFRARED INPUT MAX3130 toc15 MAX3130 toc16 2V/div RXD OUTPUT 2V/div RXD OUTPUT 2V/div INFRARED INPUT 2V/div INFRARED INPUT 2µs/div VCC = 3.3V, 115.2kbps AT 1m DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr 100µs/div VCC = 3.3V, 2400bps AT 1m DISTANCE TEMIC BPV22NF TRANSMIT POWER 200mW/sr Pin Description PIN 6 NAME FUNCTION EDGEDET 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: EdgeDetection Circuitry section. MAX3130 MAX3131 1 — — 1 RXD IR Receiver TTL/CMOS Data Output 2 2 T1IN TTL/CMOS RS-232 Transmitter Input _______________________________________________________________________________________ 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface PIN MAX3130 3 MAX3131 3 NAME FUNCTION T2IN 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. IRMODE 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. 4 — — 4 TXD IR Transmitter TTL/CMOS Data Input 5 5 R1OUT TTL/CMOS RS-232 Receiver Output 6 6 R1IN 7 7 T1OUT 8 8 BAUD16 RS-232 Receiver Input RS-232 Transmitter Output 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 VCC to disable the ENDEC. 9 9 GND Ground 10 10 VCC 3.0V to 5.5V Supply Voltage 11, 18 11, 18 N.C. No Connection. Do not make connections to these pins. 12 12 AVCC Analog Supply Voltage VCC for IR Signal Processing. AVCC range is 3.0V to 5.5V. 13 13 AGND Analog Ground for IR Signal Processing. Connect to GND. 14 14 PINC Silicon PIN Photodiode Input. Connect PINC to the cathode of the PIN photodiode. Connect the anode of the PIN photodiode to GND. 15 15 IRSD Shutdown Input for the IrDA Transceiver Circuitry 16 16 PGND Power Ground for IR LED Driver. Connect to GND. 17 17 LEDC Open-Drain Output for Driving the IR LED. Connect LEDC to the cathode of the IR LED. 19 19 V+ 20 20 C1+ Positive Terminal of the Voltage-Doubling Charge-Pump Capacitor 21 21 C1- Negative Terminal of the Voltage-Doubling Charge-Pump Capacitor 22 22 C2+ Positive Terminal of the Inverting Charge-Pump Capacitor 23 23 C2- Negative Terminal of the Inverting Charge-Pump Capacitor 24 24 V- 25 25 RSSD Shutdown Input for the RS-232 Transmitters and Charge Pump 26 26 T2OUT RS-232 Transmitter Output 27 27 R2IN 28 28 R2OUT +5.5V Generated by the Internal Charge Pump -5.5V Generated by the Internal Charge Pump RS-232 Receiver Input 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. _______________________________________________________________________________________ 7 MAX3130/MAX3131 Pin Description (continued) MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface MAX3130 Function Table MAX3130 CONTROL INPUTS RSSD IRMODE LOGIC INPUTS IRSD T1IN T2IN IrDA Input IrDA Input RS-232 I/O T1OUT LOGIC OUTPUTS IrDA OUTPUT IrDA INPUT T2OUT R1IN R2IN R1OUT R2OUT LEDC PINC High-Z High-Z RS-232 Input RS-232 Input RS-232 Output IrDA Output Enabled Disabled High-Z High-Z RS-232 Input RS-232 Input RS-232 Output IrDA Output Enabled Enabled X 0 0 RS-232 Input X 0 1 RS-232 Input 0 1 0 RS-232 RS-232 Input Input High-Z High-Z RS-232 Input RS-232 Input RS-232 Output RS-232 Output Disabled Disabled 0 1 1 RS-232 RS-232 Input Input High-Z High-Z RS-232 Input RS-232 Input RS-232 Output RS-232 Output Disabled Enabled 1 1 0 RS-232 RS-232 RS-232 Input Input Output RS-232 Output RS-232 Input RS-232 Input RS-232 Output RS-232 Output Disabled Disabled 1 1 1 RS-232 RS-232 RS-232 Input Input Output RS-232 Output RS-232 Input RS-232 Input RS-232 Output RS-232 Output Disabled Enabled X = Don’t care 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 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 10-8 at 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. 8 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). _______________________________________________________________________________________ 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface MAX3130/MAX3131 ON RSSD C1+ C1 SHDN C1- V+ V- CHARGE PUMP C2+ C2 C3 C4 C2R1OUT RECEIVE LOGIC OUTPUTS OFF R1IN 5k RS-232 INPUTS R2IN R2OUT 5k EDGE T1OUT T1IN TRANSMIT LOGIC INPUTS T2IN T2OUT RS-232 OUTPUTS 232 IRMODE IR BAUD16 Rx TxIN ENDEC RxIN Tx EDGEDET EDGE fBAUD16 VCC GND 1µF RSET MAX3130 LEDC PGND PINC ON OFF IRSD BIAS 1.2V AVCC AGND 1µF Figure 1. MAX3130 Functional Diagram _______________________________________________________________________________________ 9 MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface ON C1+ C1 C1- V- C3 C4 C2R1OUT RS-232 RECEIVE LOGIC OUTPUTS OFF V+ CHARGE PUMP C2+ C2 RSSD SHDN R1IN RS-232 INPUTS 5k R2IN R2OUT 5k RS-232 TRANSMIT LOGIC INPUTS IrDA TRANSMIT LOGIC INPUT T1IN T1OUT T2IN T2OUT RS-232 OUTPUTS TXD RXD IrDA RECEIVE LOGIC OUTPUT BAUD16 Rx TxIN ENDEC Tx RxIN MAX3131 VCC GND 1µF fBAUD16 RSET LEDC PGND PINC ON OFF IRSD BIAS 1.2V AVCC AGND 1µF Figure 2. MAX3131 Functional Diagram 10 ______________________________________________________________________________________ 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface 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). 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 Table 1. EDGEDET Operation IRSD RSSD IRMODE R2IN X X 0 X X 0 X X 1 X X X 1 X IrDA RxIN EDGEDET* X X X = Don’t care * EDGEDET is cleared by any transition on IRMODE. INFRARED PHOTODIODE INPUT * 1.41µs < t < 3CS 16CS R2OUT (RXD) WITH ENDEC DISABLED R2OUT (RXD) WITH ENDEC ENABLED 16CS 32CS CS = BAUD16 CLOCK CYCLES * HIGH = INFRARED LIGHT PULSE ( ) ARE FOR MAX3131 Figure 3a. ENDEC Operation, Receiving Infrared ______________________________________________________________________________________ 11 MAX3130/MAX3131 EDGEDET: Edge-Detection Circuitry (MAX3130) 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. MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface T2IN (TXD) 7CS INFRARED LED OUTPUT * 3CS 16CS CS = BAUD16 CLOCK CYCLES * HIGH = INFRARED LIGHT PULSE ( ) ARE FOR MAX3131 Figure 3b. ENDEC Operation, Transmitting Infrared 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 VCC or 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). LapLink is a trademark of Traveling Software. 12 __________ Applications Information Shutdown The MAX3130/MAX3131 have split analog and digital supplies (V CC and AV CC ) with separate shutdown modes. When IRSD is pulled low, the IR receiver is disabled and AVCC current 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 VCC current 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 (VIRLED) 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 current-setting resistor based on the following equation: RSET = (VCC - VIRLED - VLEDC) / ISET Using the HP HSDL-4220 IR LED as an example: VCC = 5V, ISET = 100mA, VIRLED = 1.67V VLEDC = 90mV RSET = (5V - 1.67V - 90mV) / 0.1A = 32.4Ω ______________________________________________________________________________________ 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface Use the following equations to calculate the power dissipation in each component: MAX3130 power dissipation = ISET · VDRV · duty cycle IR LED power dissipation = ISET · VIRLED · duty cycle RSET power dissipation = ISET2 · RSET · 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: IPIN = (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 AVCC and V CC pins. 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 AVCC bypass 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. ______________________________________________________________________________________ 13 MAX3130/MAX3131 Power dissipation of the MAX3130/MAX3131, IR LED, and RSET are based on the maximum LED current and duty cycle. MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface Table 2. Required Capacitor Values VCC (V) C1 (µF) 3.0 to 3.6 0.1 C2, C3, C4 (µF) 0.1 4.5 to 5.5 0.047 0.33 3.0 to 5.5 0.1 0.47 STANDARD NON-IrDA UART µP MAX3130 RTS CTS T1IN R1OUT Tx Rx T2IN R2OUT LEDC BAUD16 PINC T1OUT R1IN T2OUT R2IN DB-9 RS-232 1 2 3 4 5 6 7 8 9 IrDA BAUD16 IRMODE 232 IrDA I/O Figure 4. Using the MAX3130 and a Single UART to Perform Both IrDA and RS-232 Communication SPI µP NON-IrDA UART TX RX BAUD16 DIN DOUT SCLK CS MAX3100 UART2 RTS MAX3131 CTS T1IN R1OUT T1OUT R1IN Tx Rx T2IN R2OUT T2OUT DB-9 RS-232 R2IN LEDC TXD RXD BAUD16 IrDA PINC (UART1) Figure 5. Using the MAX3131 and Two UARTs to Perform Simultaneous IrDA and RS-232 Communication 14 ______________________________________________________________________________________ 1 2 3 4 5 6 7 8 9 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface TRANSISTOR COUNT: 1039 SSOP.EPS ________________________________________________________Package Information ______________________________________________________________________________________ 15 MAX3130/MAX3131 Chip Information MAX3130/MAX3131 3V to 5.5V, IrDA Infrared Transceiver with Integrated RS-232 Interface NOTES 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.