19-1390; Rev 0; 10/98 Low-Profile, 3V, 120µA, IrDA Infrared Transceiver 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 operating 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 components: photodiode, infrared LED, and current-setting resistor. Optical components are external to allow maximum 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 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 Ordering Information PART TEMP. RANGE MAX3120CUA 0°C to +70°C 8 µMAX PIN-PACKAGE MAX3120CSA MAX3120EUA MAX3120ESA 0°C to +70°C -40°C to +85°C -40°C to +85°C 8 SO 8 µMAX 8 SO Personal Digital Assistants (PDAs) Palmtop Computers Cell Phones Hand-Held Equipment Typical Operating Circuit Peripherals +3.3V Pin Configuration VCC VCC SHDN CS TOP VIEW LED TX SCLK TXD LEDC DIN DOUT TXD 1 8 RXD VCC 2 7 LEDC GND 3 6 PGND PINC 4 5 SHDN MAX3120 µMAX/SO MAX3100 MAX3120 RX GND RXD GND PINC PGND PIN DIODE ________________________________________________________________ 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. MAX3120 General Description MAX3120 Low-Profile, 3V, 120µA, IrDA Infrared Transceiver ABSOLUTE MAXIMUM RATINGS (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 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 = +3.0V to +5.5V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C and VCC = +3.3V.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 120 200 µA 0.01 1.0 µA 0.8 V DC CHARACTERISTICS Supply Current Shutdown Supply Current ICC TA = +25°C, SHDN = VCC (Note 1) ICC(SHDN) TA = +25°C, SHDN = GND (Note 1) LOGIC INPUTS (TXD, SHDN) Input Logic Threshold Low Input Logic Threshold High Input Leakage Current Input Capacitance VIL VIH VCC = 3.3V 2.0 VCC = 5.0V 2.4 ILEAK V -1 CIN 1 2 µA pF LOGIC OUTPUT (RXD) VOL Output Voltage Output Rise and Fall Time IR RECEIVER Supported Data Rates Equivalent Input Noise Current Input Current Sensitivity Ambient DC Current Rejection Shutdown Time ISINK = 200µA VOH ISOURCE = 100µA tr, tf CLOAD = 50pF (Note 2) (Note 3) VCC = 3.3V VCC = 5.0V Delay until ICC < 1µA Delay until maximum IR receiver data rate is valid IR Receiver Output Pulse Width Data rate = 2.4kbps Data rate = 115.2kbps 0.4 VCC 0.05 V 50 ns 2.4 INOISE Shutdown Disable Time 2 0.1 VCC 0.5 115.2 10 0.0002 6 100 375 10 µA µs 300 1 1 _______________________________________________________________________________________ kbps nARMS mA µs 90 8 µs Low-Profile, 3V, 120µA, IrDA Infrared Transceiver MAX3120 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.) PARAMETER SYMBOL IR TRANSMITTER Transmitter Rise Time Transmitter Fall Time CONDITIONS tr tf MIN 10% to 90% of 200mA drive current 90% to 10% of 200mA drive current VCC = 3.3V IOUT = 200mA VCC = 5.0V Transmitter Output Resistance Off-Leakage Current TYP MAX UNITS 20 20 1.15 0.9 0.01 600 600 2.0 1.6 10 ns ns Ω µA 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. Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. TEMPERATURE LED DRIVER ON-RESISTANCE vs. TEMPERATURE 130 SUPPLY CURRENT (µA) VCC = 3.3V 1.0 VCC = 5V 0.8 VCC = 3V 110 100 0.6 90 -40 -15 10 35 60 85 -40 -15 10 35 60 TEMPERATURE (°C) TEMPERATURE (°C) SUPPLY CURRENT vs. SUPPLY VOLTAGE LEDC VOLTAGE vs. LEDC CURRENT 600 MAX3120 TOC03 135 130 PULSED AT 20% DUTY CYCLE 500 85 400 125 VLEDC (mV) SUPPLY CURRENT (µA) VCC = 5V 120 MAX3120 toc04 RLEDC (Ω) 1.4 MAX3120 TOC02 ILEDC = 100mA 1.2 140 MAX3120 TOC01 1.6 120 VCC = 3.3V 300 115 200 110 100 VCC = 5V 0 105 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 100 150 200 250 300 350 400 LEDC CURRENT (mA) _______________________________________________________________________________________ 3 Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) AMBIENT PHOTODIODE CURRENT REJECTION vs. SUPPLY VOLTAGE 300 250 200 150 100 4.0 60 40 20 MAX3120 TOC07 80 RXD PULSE WIDTH (µs) 350 TRANSMITTER POWER = 200mW/sr INPUT PULSE WIDTH = 78µs TEMIC BPV22NF VCC = 3.3V 3.5 RXD PULSE WIDTH (µs) 100 MAX3120 TOC06 400 RXD OUTPUT PULSE WIDTH vs. DISTANCE RXD OUTPUT PULSE WIDTH vs. DISTANCE MAX3120 TOC05 450 CURRENT REJECTION (µA) MAX3120 Low-Profile, 3V, 120µA, IrDA Infrared Transceiver 3.0 2.5 2.0 TRANSMITTER POWER = 200mW/sr INPUT PULSE WIDTH = 1.63µs TEMIC BPV22NF VCC = 3.3V 1.5 50 1.0 0 0 3.0 3.5 4.0 4.5 5.0 5.5 0 20 2V/div 100 0 20 40 60 80 DISTANCE (cm) RXD OUTPUT vs. INFRARED INPUT MAX3120 toc09 RXD OUTPUT 2V/div RXD OUTPUT INFRARED INPUT 2V/div INFRARED INPUT 2µs/div VCC = 3.3V, 115.2kbps AT 1cm DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr 100µs/div VCC = 3.3V, 2400bps AT 1cm DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr RXD OUTPUT vs. INFRARED INPUT MAX3120 toc10 MAX3120 toc11 2V/div RXD OUTPUT 2V/div RXD OUTPUT 2V/div INFRARED INPUT 2V/div INFRARED INPUT 2µs/div VCC = 3.3V, 115.2kbps AT 10cm DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr 4 80 MAX3120 toc08 2V/div RXD OUTPUT vs. INFRARED INPUT 60 DISTANCE (cm) SUPPLY VOLTAGE (V) RXD OUTPUT vs. INFRARED INPUT 40 100µs/div VCC = 3.3V, 2400bps AT 10cm DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr _______________________________________________________________________________________ 100 Low-Profile, 3V, 120µA, IrDA Infrared Transceiver RXD OUTPUT vs. INFRARED INPUT RXD OUTPUT vs. INFRARED INPUT MAX3120 toc12 2V/div RXD OUTPUT 2V/div INFRARED INPUT MAX3120 toc13 2V/div RXD OUTPUT 2V/div INFRARED INPUT 100µs/div VCC = 3.3V, 2400bps AT 1m DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr 2µs/div VCC = 3.3V, 115.2kbps AT 1m DISTANCE, TERMIC BPV22NF, TRANSMIT POWER 200mW/sr Pin Description PIN NAME 1 TXD IR Transmitter TTL/CMOS Data Input. High = LED on. FUNCTION 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. 5 SHDN Shutdown Input. Active low. 6 PGND Power Ground. Ground for IR LED driver. Connect PGND to GND. 7 LEDC LED Driver Output. Connect cathode of IR-emitting LED to LEDC. 8 RXD IR Receiver TTL/CMOS Data Output. Pulses low for IR input pulse. 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 resulting 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). _______________________________________________________________________________________ 5 MAX3120 Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) MAX3120 Low-Profile, 3V, 120µA, IrDA Infrared Transceiver RXD TXD IPIN = (4µW/cm2 )(0.075cm2 )(1.8)(0.95)2 (0.6A/W) LEDC = 291nA PGND BANDPASS FILTER PINC + GND BIAS MAX3120 SHDN 1.2V VCC Figure 1. Functional Diagram Transmitter The MAX3120’s IR transmitter consists of a high-power MOS switch, capable of quickly switching 200mA with less than 2Ω of 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 appropriate 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 component power dissipation in high-duty-cycle transmit schemes. 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 example, 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 performance by increasing the noise gain of the input transimpedance 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 discussed 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 current-setting resistor based on the following equation: 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. RSET = VCC - VLED - VLEDC ISET 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 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 equation to determine if the Temic BPV22NF meets these requirements: 6 _______________________________________________________________________________________ Low-Profile, 3V, 120µA, IrDA Infrared Transceiver 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 photodiode 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 minimize 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 minimize 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 coupling back to the input via parasitic capacitance. Chip Information TRANSISTOR COUNT: 256 Package Information _______________________________________________________________________________________ 7 MAX3120 Power-dissipation requirements of the MAX3120, IR LED, and RSET must be met based on maximum duty cycle and output current requirements. Low-Profile, 3V, 120µA, IrDA Infrared Transceiver SOICN.EPS MAX3120 Package Information (continued) 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. 8 _____________________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.