LT1328 4Mbps IrDA Infrared Receiver U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ The LT ®1328 is a photodiode receiver that supports IrDA® data rates up to 4Mbps as well as other modulation methods such as Sharp ASK and TV remote control. The LT1328 MSOP contains all the necessary circuitry to convert current pulses from an external photodiode to a digital TTL output while rejecting unwanted lower frequency interference. The LT1328 plus five external components is all that is required to make an IrDA compatible receiver. SIR, FIR and 4ppm Compatible Low Frequency Ambient Rejection Loop Supply Current: 2mA 8-Lead MSOP and SO Packages 5V Single Supply Operation Optional High Frequency Noise Rejection U APPLICATIONS ■ ■ ■ ■ ■ ■ ■ ■ IrDA Applications Sharp/Newton TV Remote Noncontact Telemetry Wireless Slave for Photographic Flash Keyless Entry Optical Data Transfer Infrared Home Control Systems Power requirements for the LT1328 are minimal—a single 5V supply and 2mA of quiescent current. Internal highpass filtering attenuates interfering signals such as sunlight, incandescent and fluorescent lamps and is selectable at Pin 7 for low or high data rates. The LT1328’s ease of use and flexibility make it an ideal solution for numerous other photodiode receiver applications. The LT1328 is available in the SO-8 as well as the tiny MSOP for size-critical applications. , LTC and LT are registered trademarks of Linear Technology Corporation. IrDA is a registered trademark of the Infrared Data Association. U TYPICAL APPLICATIONS N IrDA Receiver C6 1000pF LT1328 1 LIGHT IN TEMIC BPV22NF D1 IN VBIAS IrDA Transmitter HIGH: SIR LOW: FIR AND 4ppm (OPTIONAL) 8 2 C1 10nF C4 330pF 7 FILTER MODE 3 FILTER 6 VCC SWITCH 4 5 DATA GND TTL DATA OUT 5V VCC OPTIONAL SHUTDOWN CIRCUIT C5 4.7µF TP0610L* R1 100Ω 5V C2 4.7µF ENABLE *SILICONIX TRANSMIT INPUT R2 10k *HEWLETT PACKARD D2 HSDL-4220* R3 3.9Ω 1/2W Q3 2N7002 1328 TA02 1328 TA01 1 LT1328 W W U W ABSOLUTE MAXIMUM RATINGS Total Supply Voltage (VCC to GND) ........................... 6V Differential Voltage (Any Two Pins) .......................... 6V Operating Temperature Range .................... 0°C to 70°C Specified Temperature Range ..................... 0°C to 70°C Maximum Junction Temperature ......................... 150°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C U W U PACKAGE/ORDER INFORMATION ORDER PART NUMBER TOP VIEW IN FILTER FILTER SWITCH GND 1 2 3 4 8 7 6 5 VBIAS MODE VCC DATA MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150°C, θJA = 250°C/ W LT1328CMS8 MS8 PART MARKING ORDER PART NUMBER TOP VIEW IN 1 8 VBIAS FILTER 2 FILTER 3 SWITCH GND 4 7 MODE LT1328CS8 6 VCC 5 DATA S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO LTBG 1328 TJMAX = 150°C, θJA = 190°C/ W Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS VCC = 5V, VGND = 0V, VMODE = 2V unless otherwise specified. (Note 1) SYMBOL PARAMETER CONDITIONS ITH(MIN) Current Out of Pin 1 (SIR), Pulse Width 1.6µs, Period 8.7µs Current Out of Pin 1 (FIR, 4ppm), Pulse Width 125ns, Period 500ns Minimum Input Current Pulse MIN IPD Maximum Input Current Current Out of Pin 1 IREJECT Maximum Low Frequency Input Current DC to 120Hz, Current Out of Pin 1 IS Supply Current No Input Signal VS Operating Supply Voltage ● 4.5 VIN Bias Voltage on Pin 1 No Input Signal ● VBIAS Bias Voltage on Pin 8 No Input Signal VLT Quiescent Voltage on Pin 2 No Input Signal VTHL Switch Logic Level Low Pin 7 ● VTHH Switch Logic Level High Pin 7 ● VOL Comparator Output Low Voltage On Pin 5, 800µA Sink Current ● VOH Comparator Output High Voltage On Pin 5, 50µA Source Current ● The ● denotes specifications which apply over the full operating temperature range of 0°C ≤ TA ≤ 70°C. 2 ● 15 TYP MAX UNITS 200 nA 600 nA 30 mA 1000 µA 2 3 5.5 V 1.0 1.5 2.0 V ● 1.0 1.5 2.0 V ● 1.0 1.5 ● 2.0 V 0.8 V 2.0 V 0.4 4.0 mA 0.5 4.3 Note 1: MS8 package devices are designed for and intended to meet commercial temperature range specifications but are not tested at 0°C. V V LT1328 U W TYPICAL PERFORMANCE CHARACTERISTICS Change in Voltage on Pin 1 vs Supply Voltage Supply Current vs Supply Voltage 4 2 1 3 4 5 6 7 8 SUPPLY VOLTAGE (V) 9 0 –2 –4 10 1 0 2 3 4 5 6 7 8 SUPPLY VOLTAGE (V) 9 1328 G01 Change in Output Pulse Width vs Input Duty Cycle 100 50 0 0.1 10 1 100 1000 10 INPUT CURRENT (µA) 1328 G03 10 VS = 5V VFILT = 10nF VBIAS = 1000pF PULSE PERIOD = 8.7µs 200 150 IPIN1 = 150nA TO 3mA 100 IPIN1 > 3mA TO 10mA 50 CURRENT SINKING FROM PIN 1 0 –10 CURRENT SOURCING FROM PIN 1 –20 –30 – 40 3 30 10 INPUT DUTY CYCLE (%) 1 100 VS = 5V TA = 25°C 0.1 1 10 100 1000 10000 100000 CURRENT (PIN 1) (µA) 1328 G05 1328 G04 Change in Voltage on Pin 2 vs Current Peak Interfering Current vs Frequency 2.0 1000 VS = 5V TA = 25°C 1.5 1.0 SOURCING CURRENT 0.5 0 SINKING CURRENT – 0.5 10000 Change in Voltage on Pin 1 vs Current 250 0 150 VS = 5V VFILT = 10nF VBIAS = 1000pF FOR INPUT PULSE WIDTHS OF 8.6µs TO 0.22µs PULSE PERIOD = 8.7µs 1328 G02 CHANGE IN VOLTAGE ON PIN 1 (mV) 2 2 0.1 1 10 100 1000 10000 100000 CURRENT (PIN 1) (µA) 1328 G06 PEAK INPUT CURRENT AMPLITUDE (µA) 1 OUTPUT PULSE WIDTH 100 (%) INPUT PULSE WIDTH 0 IPIN1 = 0nA TA = 25°C OUTPUT PULSE WIDTH 100 (%) INPUT PULSE WIDTH CHANGE IN VOLTAGE ON PIN 1 (mV) 3 CHANGE IN VOLTAGE ON PIN 2 (V) SUPPLY CURRENT (mA) 200 4 IPIN1 = 0nA VPIN7 = 0V TA = 25°C 0 Change in Output Pulse Width vs Input Current Amplitude VS = 5V CBIAS = 1000pF CURRENT IS SOURCED OUT OF PIN 1 100 CFILT = 330pF 10 CFILT = 10nF 1 0.1 0.01 AREA OF SIGNAL REJECTION 0.1 10 1 FREQUENCY (kHz) 100 1000 1328 G07 3 LT1328 U U U PIN FUNCTIONS IN (Pin 1): Connect this pin to the photodiode cathode. This is the input to the preamplifier and is held at 1.5V by the output of the DC servo. To maintain the 1.5V on this pin, the DC servo can source up to 2mA or sink 40µA to this pin. GND (Pin 4): Ground. DATA (Pin 5): TTL Output of the Comparator. A TTL LOW at this pin indicates that the photodiode has received a pulse of light. This pin will remain HIGH when the light signal and noise are below the attenuation band of the DC servo. FILTER (Pin 2): Connect a capacitor from this pin to ground. The value of the capacitor will set the band of frequencies that will be attenuated by the servo. The pole is set by the formula f = 25/(2π • 60k • C). A 330pF capacitor will attenuate photodiode signals below 200kHz when operating at high data rates (FIR and 4ppm). VCC (Pin 6): 5V Supply. A bypass capacitor, connected as close as possible from Pin 6 to ground is recommended (4.7µF). MODE (Pin 7): A TTL HIGH on this pin will cause the open collector at Pin 3 to switch to ground. This is an option that switches in extra capacitance for lower frequency data rates. If this pin is not used, select a capacitor (C4) to accommodate the lowest data rate (for IrDA C4 = 10nF). FILTER SWITCH (Pin 3): Collector of a Transistor Switch. When the MODE switch (Pin 7) is TTL HIGH this pin will be switched to ground. This pin is used to increase the filter capacitor for slower data rates (SIR). A 10nF capacitor from Pin 2 to Pin 3 will bring the highpass frequency down to 6.6kHz for SIR. VBIAS (Pin 8): A 1000pF capacitor from this pin to ground is required. W BLOCK DIAGRAM VCC RFB 50k VBIAS 1.5V 8 C6 1000pF 1 IN PREAMP D1 PHOTODIODE TEMIC BPV22NF BIAS RIN 2k FILTER MODE 7 VCC 6 HIGH: SIR LOW: FIR AND 4ppm DC SERVO + 2 C4 330pF C1 10nF 3 FILTER FILTER SWITCH gm 60k 5V – C2 4.7µF 4 GND – COMPARATOR DATA 5 + 1328 BD Figure 1. LT1328 Block Diagram 4 LT1328 U W U U APPLICATIONS INFORMATION The LT1328 is a low noise, high speed, high gain infrared receiver designed to easily provide IR communications with portable computers, PDAs, desktop computers and peripherals. The receiver takes the photodiode current from an infrared photodiode (typically Temic BPV22NF) and performs a current-to-voltage conversion. Figure 1 is a block diagram of the LT1328. Photodiode current is transformed into a voltage by feedback resistor RFB. The DC level of the preamp is held at VBIAS due to the servo action of the transconductance amplifier gm. The servo action only suppresses frequencies below the Rgm, CFILT pole. This highpass filtering attenuates interfering signals such as sunlight, incandescent and fluorescent lamps. For higher data rates, the rejection band can be increased to include higher frequencies (Pin 7 LOW). If this option is not used, Pin 7 is grounded and Pin 3 is open. The rejection band of the filter is then determined by the lowest data rate; C4 equals 10nF for IrDA (SIR, FIR and 4ppm). The highpass filter break point is set by the capacitor from Pin 2 to ground at f(Hz) = 25/(2π • Rgm • C) where Rgm = 60k. The 330pF capacitor in Figure 1 sets a 200kHz corner frequency and is used for data rates above 115kbps. For low data rates (115kbps and below) Pin 7 should be set to TTL HIGH which grounds Pin 3 and reduces the break frequency with the addition of the capacitor between Pins 2 and 3. A 10nF capacitor produces a 6.6kHz corner. Signals passed by the preamp/gm amplifier combination cause the comparator output to swing low. Performance of the LT1328 circuit in Figure 1 extends over the full 1cm to 1 meter range of the IrDA standard at the stipulated light levels. For IrDA data rates of 115kbps and below, a 1.6µs pulse width is used for a logic zero and no pulse for a logic one. Light levels are 40mW/SR to 500mW/SR. Figure 2 shows a scope photo for a transmitter input (bottom trace) and the LT1328 output (top trace). Note that the input to the transmitter is inverted, i.e., a high at the input is light transmitted, which is a zero at the output of the transmitter (Pin 5). The MODE pin (Pin 7) should be high for these data rates. The second fastest tier of the IrDA standard addresses 576kbps and 1.152Mbps data rates with pulse widths of 1/4 of the bit interval for zero and no pulse for one. The NRZ DATA 0 1 0 0 1 1 0 1 0 IrDA-SIR HIGH = LIGHT TRANSMITTED 1328 F02a DATA RATES: 2400BAUD TO 115kbps BIT INTERVAL: 417µs TO 8.7µs PULSE WIDTH: 3/16 OF INTERVAL OR 1.63µs IrDA-SIR (1m) IrDA-SIR (1cm) RECEIVER OUTPUT RECEIVER OUTPUT TRANSMITTER INPUT TRANSMITTER INPUT Figure 2. IrDA-SIR Modulation 5 LT1328 U W U U APPLICATIONS INFORMATION The last IrDA encoding method is for 4Mbps and uses pulse position modulation, thus its name 4ppm. Two bits are encoded by the location of a 125ns wide pulse at one of the four positions within a 500ns interval (2 bits • 1/500ns = 4Mbps). Range and input levels are the same as for 1.152Mbps. Figure 4 shows the LT1328 reproduction of this modulation. 1.152Mbps rate, for example, uses pulses of 217ns for its bit time of 870ns. Light levels are 100mW/SR to 500mW/ SR over the 1cm to 1 meter range. A photo of a transmitted input and LT1328 output is shown in Figure 3. The LT1328 output pulse width will be less than 800ns wide over all of the above conditions at 1.152Mbps. Pin 7 should be held low for these data rates and above. NRZ DATA 0 1 0 0 1 1 0 1 0 IrDA-FIR HIGH = LIGHT TRANSMITTED 1328 F03a DATA RATES: FIXED AT 1.15Mbps BIT INTERVAL: 870ns PULSE WIDTH: 1/4 OF INTERVAL OR 217ns IrDA-FIR (1m) IrDA-FIR (1cm) RECEIVER OUTPUT RECEIVER OUTPUT TRANSMITTER INPUT TRANSMITTER INPUT Figure 3. IrDA-FIR Modulation DATA BIT PAIR 00 01 10 11 4ppm DATA SYMBOL 1000 0100 0010 0001 NRZ DATA 0 1 0 0 1 1 0 1 IrDA 4ppm HIGH = LIGHT TRANSMITTED 1328 F04a DATA RATES: FIXED AT 4Mbps BIT INTERVAL: 500ns PULSE WIDTH: 1/4 OF INTERVAL OR 125ns IrDA-4ppm(1m) IrDA-4ppm (1cm) RECEIVER OUTPUT RECEIVER OUTPUT TRANSMITTER INPUT TRANSMITTER INPUT Figure 4. IrDA-4ppm 6 0 LT1328 U W U U APPLICATIONS INFORMATION In situations where long range is not a requirement, a very simple IR link can be made using unmodulated NRZ (nonreturn to zero) data. The circuit is shown in Figure 5. A BER (bit-error rate) transmitter and receiver was used to test the data-link error rates for data rates of 375kbps. Because the NRZ data can have long stretches of continuous “1” data, the low frequency corner of the LT1328 photodiode receiver is set to 14Hz to prevent pulse-top distortion. 5V C5 4.7µF R1 100Ω R2 10k To do this, make C1 4.7µF. This is the only change from a standard IrDA-SIR receiver. A range of 24" (with a bit error rate lower than 1 in 108) is achieved with no additional processing beyond that provided by the LT1328. A caution: when using unmodulated data, it is possible to get a 100% duty cycle on the LED transmitter, so be sure that the LED can handle this. 24" D2 HSDL 4220 R3 3.9Ω 1/2W D1 TEMIC BPV22NF NC Q3 2N7002 C4 4.7µF 1 8 2 7 3 4 LT1328 C6 1000pF 6 C2 4.7µF 5 5V BIT ERROR RATE TRANSMITTER/RECEIVER 375bps NRZ DATA OUT IN 1328 F05 Figure 5. Simple NRZ Data Link 7 LT1328 U U W U APPLICATIONS INFORMATION There is one drawback to the previous scheme. Lowering the highpass frequency to 14Hz negates the normally excellent ambient light rejection of the LT1328 to lineoperated light sources. By modulating the data in a very simple and inexpensive way the ambient light rejection can be maintained. The NRZ data is used to gate a 3MHz square wave before driving the transmitter. The LT1328 in FIR-4ppm mode (bandwidth of 1MHz to 4MHz) will receive the 3MHz signal. Thus, the low frequency response is no longer required and the LT1328 can be configured as a FIR receiver with no changes. Note that when in FIR/ 4ppm mode, the LT1328 has excellent rejection to activeballast fluorescent lights (40kHz to 100kHz) as well as line operated bulbs. The data is recovered with two stages of retriggerable one-shots on the output of the LT1328. The first one-shot pulse length is set to 80ns and acts as an edge detector and the second one-shot pulse length is set to 2.3µs, just under a symbol period. With this modulation, the range can be extended to over 30" and still have a bit error rate lower than 1 in 108. 5V > 30" D2 HSDL 4220 C5 4.7µF D1 TEMIC BPV22NF R3 3.9Ω 1/2W R1 100Ω NC C4 100pF R5 46.4k 1% C8 100pF 6 BIT ERROR RATE TRANSMITTER/RECEIVER 74LS00 2 1 8 2 7 LT1328 3 C6 1000pF 6 4 C2 4.7µF 5 Q3 2N7002 R2 10k 3 1 375bps NRZ DATA OUT C7 10pF 15 7 14 1 11 5 IN R4 5k 1% 5V 1/2 74LS123 13 10 1/2 74LS123 2 3 9 3MHz 1328 F06 Figure 6. Simple Data Link with Improved Low Frequency Noise Rejection U TYPICAL APPLICATIONS N Wireless Slave for Photographic Flash R1 100Ω LIGHT FROM MASTER FLASH D1 HAMAMATSU S4797-01 C4 330pF NC 1 8 2 7 3 4 LT1328 TO HOT SHOE OF SLAVE FLASH NC 5V NC 6 R2 1k 5 R3 10k Q1 MPS2907A D2 1N4148 C2 4.7µF R5 1k Q2 MPSA42 D3 MUR 160524 R4 10k 1328 TA05 8 C5 0.1µF 5V Q1 VN2222 VIN 20V TO 400V R3 16Ω R1 1M R4 51k R6 75k R5 1M C3 1µF 6 5 4 3 – + 2 7 1 LTC1440 D4 5.6V 8 ALL RESISTORS 1%, 1/4W UNLESS OTHERWISE NOTED C5 1µF FILM R2 6.2M SET INPUT VOLTAGE TO 200V, ATTACH FREQUENCY COUNTER TO PIN 8 OF LTC1440 AND ADJUST R1 FOR 200Hz R7 50k 5W C8 0.01µF D3 1N4148 + R8 2k 13 12 10 9 1 2 C9 10µF 74HC86 7 11 8 3 C7 220pF NC 5 4 14 6 Noncontact Voltmeter D2 HSDL-4220 RANGE: 6 FT Q2 VN2222 R9 16Ω D1 TEMIC BPV22NF FREQUENCY COUNTER 1Hz = 1V C4 330pF NC 3 2 5V 14 1 4 3 2 1 1/2 LS221 C10 10nF LT1328 1328 TA06 13 15 R10 20k 5 6 7 8 + 5V C2 4.7µF 5V C6 1000pF LT1328 TYPICAL APPLICATIONS N 9 U LT1328 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.10) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.10) 0.192 ± 0.004 (4.88 ± 0.10) 1 2 3 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.006 ± 0.004 (0.15 ± 0.10) 0° – 6° TYP 0.021 ± 0.004 (0.53 ± 0.01) SEATING PLANE 0.012 (0.30) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 10 4 0.025 (0.65) TYP MSOP08 0596 LT1328 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 2 3 0.053 – 0.069 (1.346 – 1.752) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 4 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) TYP SO8 0996 11 LT1328 U TYPICAL APPLICATIONS N IrDA Receiver C6 1000pF LT1328 1 D1 BPV22NF* C1 10nF *TEMIC IN 2 SHDN IrDA Transmitter JP1 VCC 1 2 3 8 7 E2 MODE FILTER MODE 3 FILTER 6 VCC SWITCH 4 5 DATA GND C4 330pF C5 4.7µF VCC R1 100Ω 5% E3 VCC E4 DATA C2 4.7µF E6 TRANS R2 10k 5% E1 GND D2 HSDL-4220* R3 3.9Ω 1/2W Q1 2N7002 E5 GND 1328 TA03 *HEWLETT PACKARD 1328 TA04 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1016 UltraFastTM Precision Comparator 10ns Prop Delay LT1116 Single Supply, Ground Sensing Comparator 12ns Prop Delay LT1319 Multiple Modulation Standard Infrared Receiver Supports IrDA, SIR and FIR, Sharp/Newton and TV Remote LT1361 Dual 4mA, 50MHz, 800V/µs Op Amp C-LoadTM Op Amp Stable with All Capacitive Loads UltraFast and C-Load are trademarks of Linear Technology Corporation. 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com 1328f LT/TP 0597 7K • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1997