LT1237 5V RS232 Transceiver with Advanced Power Management and One Receiver Active in Shutdown U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO One Receiver Remains Active While in Shutdown ESD Protection over ±15kV Uses Small Capacitors: 0.1µF, 0.2µF, 1.0µF 60µA Supply Current in Shutdown Pin Compatible with LT1137A 120kBaud Operation for RL = 3k, CL = 2500pF 250kBaud Operation for RL = 3k, CL = 1000pF Operates to 120kBaud CMOS Comparable Low Power 30mW Operates from a Single 5V Supply Easy PC Layout—Flowthrough Architecture Rugged Bipolar Design Outputs Assume a High Impedance State When Off or Powered Down Absolutely No Latchup Available in SO and SSOP Packages U APPLICATIO S ■ ■ The LT®1237 is an advanced low power three driver, five receiver RS232 transceiver. Included on the chip is a shutdown pin for reducing supply current near zero. During shutdown one receiver remains active to detect incoming RS232 signals, for example, to wake up a system. The LT1237 is fully compliant with all EIA RS232 specifications. New ESD structures on the chip allow the LT1237 to survive multiple ±15kV strikes, eliminating the need for costly TransZorbs® on the RS232 line pins. The LT1237 operates in excess of 120kbaud even driving heavy capacitive loads. Two shutdown modes allow the driver outputs to be shut down separately from the receivers for more versatile control of the RS232 interface. During shutdown, drivers and receivers assume a high impedance state. , LTC and LT are registered trademarks of Linear Technology Corporation. TransZorb is a registered trademark of General Instruments, GSI Notebook Computers Palmtop Computers U TYPICAL APPLICATIO Output Waveforms V+ 1.0µF 5V VCC 2 × 0.1µF DRIVER 1 OUT RX1 IN DRIVER 2 OUT TO LINE RX2 IN RX3 IN RX4 IN DRIVER 3 OUT RX5 IN (LOW-Q) ON/OFF 1 2 28 LT1237 V– 27 3 26 4 25 5 24 6 23 7 22 8 21 9 20 10 19 11 18 12 17 13 16 14 15 0.1µF RECEIVER OUTPUT CL = 50pF 2 × 0.1µF DRIVER 1 IN RX1 OUT DRIVER 2 IN RX2 OUT TO LOGIC R DRIVER OUTPUT RL = 3k CL = 2500pF RX3 OUT RX4 OUT DRIVER 3 IN RX5 OUT (LOW-Q) GND DRIVER DISABLE INPUT RING DETECT IN µCONTROLLER OR µPROCESSOR 1237 TA02 SHUTDOWN CONTROL OUT LT1237 TA01 1 LT1237 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ................................................ 6V V + ........................................................................ 13.2V V – ...................................................................... –13.2V Input Voltage Driver ........................................................... V – to V + Receiver ............................................... – 30V to 30V Output Voltage Driver .................................................... – 30V to 30V Receiver .................................... – 0.3V to VCC + 0.3V Short Circuit Duration V + ................................................................... 30 sec V – ................................................................... 30 sec Driver Output .............................................. Indefinite Receiver Output .......................................... Indefinite Operating Temperature Range LT1237C ................................................. 0°C to 70°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C ORDER PART NUMBER TOP VIEW V+ 1 28 V – 27 C2 – 5V VCC 2 C1 + 3 26 C2+ C1 – 4 25 DR1 IN DR1 OUT 5 24 RX1 OUT RX1 IN 6 LT1237CG LT1237CNW LT1237CSW 23 DR2 IN DR2 OUT 7 22 RX2 OUT RX2 IN 8 21 RX3 OUT RX3 IN 9 20 RX4 OUT RX4 IN 10 19 DR3 IN RX5 OUT 18 (LOW-Q) 17 GND 16 DRIVER DISABLE 15 NC DR3 OUT 11 RX5 IN 12 (LOW-Q) ON/OFF 13 NC 14 G PACKAGE NW PACKAGE 28-LEAD PLASTIC SSOP 28-LEAD (WIDE) PDIP SW PACKAGE 28-LEAD (WIDE) PLASTIC SO TJMAX = 150°C, θJA = 96°C/ W (G) TJMAX = 150°C, θJA = 56°C/ W (NW) TJMAX = 150°C, θJA = 85°C/ W (SW) Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER Power Supply Generator V + Output V – Output Supply Current (VCC) CONDITIONS MIN 7.9 –7 6 6 0.06 3.00 2 TA = 25°C (Note 3) ● Supply Current when OFF (VCC) Supply Rise Time Shutdown to Turn-On ON/OFF Pin Thresholds ON/OFF Pin Current DRIVER DISABLE Pin Thresholds DRIVER DISABLE Pin Current Oscillator Frequency 2 Shutdown (Note 4) Driver Disable C1 = C2 = 0.2µF, C + = 1.0µF, C – = 0.1µF Input Low Level (Drivers Enabled) Input High Level (Drivers Disabled) 0V ≤ VON/OFF ≤ 5V Input Low Level (Drivers Enabled) Input High Level (Drivers Disabled) 0V ≤ VDRIVER DISABLE ≤ 5V Driver Outputs Loaded RL = 3k ● 0.8 ● ● ● ● TYP –15 0.8 1.2 1.6 1.4 1.4 –10 130 MAX UNITS 12 14 0.15 V V mA mA mA mA ms 2.4 80 2.4 500 V V µA V V µA kHz LT1237 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER CONDITIONS Any Driver Output Voltage Swing Load = 3k to GND Logic Input Voltage Level Logic Input Current Output Short-Circuit Current Output Leakage Current Data Rate (Note 7) Slew Rate Propagation Delay Any Receiver Input Voltage Thresholds Hysteresis Input Resistance Output Leakage Current Receivers 1, 2, 3, 4 Output Voltage Output Short-Circuit Current Propagation Delay Receiver 5 (LOW ISUPPLY RX) Output Voltage Output Short-Circuit Current Propagation Delay Positive Negative Input Low Level (VOUT = High) Input High Level (VOUT = Low) 0.8V ≤ VIN ≤ 2V VOUT = 0V Shutdown VOUT = ±30V (Note 4) RL = 3k, CL = 2500pF RL = 3k, CL = 1000pF RL = 3k, CL = 51pF RL = 3k, CL = 2500pF Output Transition tHL High to Low (Note 5) Output Transition tLH Low to High ● ● ● ● TYP 5.0 7.5 – 6.3 1.4 1.4 5 17 10 2.0 ● ±9 ● 4 0.8 ● VIN = ±10V Shutdown (Note 4) 0 ≤ VOUT ≤ VCC MAX 0.1 3 ● Output Low, IOUT = – 1.6mA Output High, IOUT = 160µA (VCC = 5V) Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Output Transition tHL High to Low (Note 6) Output Transition tLH Low to High ● ● Output Low, IOUT = – 500µA Output High, IOUT = 160µA (VCC = 5V) Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Output Transition tHL High to Low (Note 6) Output Transition tLH Low to High ● ● 3.5 – 10 10 3.5 –2 2 UNITS 15 7 0.6 0.5 1.3 1.3 V V V V µA mA µA kBaud kBaud V/µs V/µs µs µs 1.3 1.7 0.4 5 1 2.4 1.0 7 10 V V V kΩ µA – 5.0 0.8 20 100 120 250 Input Low Threshold (VOUT = High) Input High Threshold (VOUT = Low) Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Testing done at VCC = 5V and VON/OFF = 3V, unless otherwise specified. Note 3: Supply current is measured as the average over several charge pump burst cycles. C + = 1.0µF, C – = 0.1µF, C1 = C2 = 0.2µF. All outputs are open, with all driver inputs tied high. Note 4: Measurements in shutdown are performed with VON/OFF ≤ 0.1V. Supply current measurements using driver disable are performed with VDRIVER DISABLE ≥ 3V. MIN 0.2 4.2 – 20 20 250 350 0.2 4.2 –4 4 1.0 0.6 30 0.4 600 600 0.4 3 3 V V mA mA ns ns V V mA mA µs µs Note 5: For driver delay measurements, RL = 3k and CL = 51pF. Trigger points are set between the driver’s input logic threshold and the output transition to the zero crossing (t HL = 1.4V to 0V and tLH = 1.4V to 0V). Note 6: For receiver delay measurements, CL = 51pF. Trigger points are set between the receiver’s input logic threshold and the output transition to standard TTL/CMOS logic threshold (t HL = 1.3V to 2.4V and tLH = 1.7V to 0.8V). Note 7: Data rate operation guaranteed by slew rate, short-circuit current and propagation delay tests. 3 LT1237 U W TYPICAL PERFOR A CE CHARACTERISTICS Receiver Input Thresholds Driver Output Voltage VCC = 5V OUTPUT HIGH 2.75 VCC = 4.5V 6 4 2 0 –2 –4 OUTPUT LOW VCC = 4.5V –6 VCC = 5V –8 –10 –55 –25 50 25 0 75 TEMPERATURE (°C) 100 80 2.50 2.25 2.00 INPUT HIGH 1.75 1.50 INPUT LOW 1.25 1.00 50 25 0 75 TEMPERATURE (°C) Supply Current in Shutdown 40 30 20 100 0 125 0 125 4 2.5 50 THRESHOLD VOLTAGE (V) 150 3.0 75 3 2 1 25 50 25 75 0 TEMPERATURE (°C) 100 0 –55 –25 125 50 25 0 75 TEMPERATURE (°C) 35 SUPPLY CURRENT (mA) ON THRESHOLD 1.5 1.0 OFF THRESHOLD 0.5 1.0 0 –55 –25 125 50 25 75 0 TEMPERATURE (°C) 100 30 1237 G06 Driver Leakage in Shutdown 100 3 DRIVERS LOADED RL = 3k 25 20 1 DRIVER LOADED RL = 3k 15 10 125 NO LOAD 10 1 VOUT = 30V VOUT = –30V 5 50 25 75 0 TEMPERATURE (°C) 100 125 1237 G07 4 100 40 2.5 0 –55 –25 1.5 Supply Current ON/OFF Thresholds 3.0 150 2.0 1237 G05 1237 G04 2.0 125 0.5 LEAKAGE CURRENT (µA) 0 –55 –25 75 50 100 DATA RATE (kBAUD) DRIVER DISABLE Threshold Supply Current in Driver Disable 100 25 1237 G03 5 SUPPLY CURRENT (mA) SUPPLY CURRENT (µA) 50 1237 G02 1237 G01 THRESHOLD VOLTAGE (V) 60 10 0.75 0.50 –55 –25 125 3 DRIVERS ACTIVE RL = 3k CL = 2500pF 70 SUPPLY CURRENT (mA) RL = 3k THRESHOLD VOLTAGE (V) DRIVER OUTPUT VOLTAGE (V) 8 Supply Current vs Data Rate 3.00 10 0 –55 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1237 G08 0.1 –55 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1237 G09 LT1237 U W TYPICAL PERFOR A CE CHARACTERISTICS Driver Short-Circuit Current Receiver Short-Circuit Current 50 25 SHORT-CIRCUIT CURRENT (mA) SHORT-CIRCUIT CURRENT (mA) 30 ISC+ 20 15 ISC– 10 5 0 –55 –25 50 25 75 0 TEMPERATURE (°C) 100 125 40 RX1 TO RX4 ISC– 30 RX1 TO RX4 ISC+ 20 RX5 ISC – 10 RX5 ISC+ 0 –55 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1237 G11 1237 G10 Driver Output Waveforms Receiver Output Waveforms RX5 OUTPUT CL = 50pF DRIVER OUTPUT RL = 3k CL = 2500pF RX1 TO RX4 OUTPUT CL = 50pF DRIVER OUTPUT RL = 3k INPUT INPUT 1237 G12 1237 G13 U U U PI FU CTIO S VCC: 5V Input Supply Pin. This pin should be decoupled with a 0.1µF ceramic capacitor close to the package pin. Insufficient supply bypassing can result in low output drive levels and erratic charge pump operation. GND: Ground Pin. ON/OFF: TTL/CMOS Compatible Operating Mode Control. A logic low puts the device in the low power shutdown mode. All three drivers and four receivers (RX1, RX2, RX3, and RX4) assume a high impedance output state in shutdown. Only receiver RX5 remains active while the transceiver is in shutdown. The transceiver consumes only 60µA of supply current while in shutdown. A logic high fully enables the transceiver. DRIVER DISABLE: This pin provides an alternate control for the charge pump and RS232 drivers. A logic high on this pin shuts down the charge pump and places all driver outputs in a high impedance state. All five receivers remain active under these conditions. Floating the driver disable pin or driving it to a logic low level fully enables the transceiver. A logic low on the ON/OFF pin supersedes the state of the DRIVER DISABLE pin. Supply current drops to 3mA when in driver disable mode. V +: Positive Supply Output (RS232 Drivers). V + ≈ 2VCC – 1.5V. This pin requires an external charge storage capacitor C ≥ 1.0µF, tied to ground or VCC. Larger value capacitors may be used to reduce supply ripple. The ratio of the capacitors on V + and V – should be greater than 5 to 1. V –: Negative Supply Output (RS232 Drivers). V – ≈ –(2VCC – 2.5V). This pin requires an external charge storage capacitor C ≥ 0.1µF. See the Applications Information section for guidance in choosing filter capacitors for V + and V –. 5 LT1237 U U U PI FU CTIO S C1+, C1–, C2+, C2 –: Commutating Capacitor Inputs, require two external capacitors C ≥ 0.2µF: one from C1+ to C1–, and another from C2 + to C2 –. The capacitor’s effective series resistance should be less than 2Ω. For C ≥ 1µF, low ESR tantalum capacitors work well in this application, although small value ceramic capacitors may be used with a minimal reduction in charge pump compliance. DRIVER IN: RS232 Driver Input Pins. These inputs are TTL/CMOS compatible. Inputs should not be allowed to float. Tie unused inputs to VCC. DRIVER OUT: Driver Outputs at RS232 Voltage Levels. Driver output swing meets RS232 levels for loads up to 3k. Slew rates are controlled for lightly loaded lines. Output current capability is sufficient for load conditions up to 2500pF. Outputs are in a high impedance state when in shutdown mode, VCC = 0V, or when the DRIVER DISABLE pin is active. Outputs are fully short-circuit protected from V – + 30V to V + – 30V. Applying higher voltages will not damage the device if the overdrive is moderately current limited. Short circuits on one output can load the power supply generator and may disrupt the signal levels of the other outputs. The driver outputs are protected against ESD to ±15kV for human body model discharges, ±8kV for IEC 1000-4-2 contact mode discharges and ±15kV for IEC 1000-4-2 air gap discharges. RX IN: Receiver Inputs. These pins accept RS232 level signals (±30V) into a protected 5k terminating resistor. The receiver inputs are protected against ESD to ±15kV for human body model discharges, ±8kV for IEC 1000-4-2 contact mode discharges and ±15kV for IEC 1000-4-2 air gap discharges. Each receiver provides 0.4V of hysteresis for noise immunity. Open receiver inputs assume a logic low state. RX OUT: Receiver Outputs with TTL/CMOS Voltage Levels. Outputs RX1, RX2, RX3, and RX4 are in a high impedance state when in shutdown mode to allow data line sharing. Outputs, including LOW-Q RX OUT, are fully short-circuit protected to ground or VCC with the power on, off, or in shutdown mode. LOW Q-CURRENT RX IN: Low Power Receiver Input. This special receiver remains active when the part is in shutdown mode, consuming typically 60µA. This receiver has the same 5k input impedance and ±10kV ESD protection characteristics as the other receivers. LOW Q-CURRENT RX OUT: Low Power Receiver Output. This pin produces the same TTL/CMOS output voltage levels as receivers RX1, RX2, RX3, and RX4 with slightly decreased speed and short-circuit current. Data rates to 120kbaud are supported by this receiver. U ESD PROTECTIO The RS232 line inputs of the LT1237 have on-chip protection from ESD transients up to ±15kV for human body discharges, ±8kV for IEC 1000-4-2 contact mode discharges and ±15V for IEC 1000-4-2 air gap discharges. The protection structures act to divert the static discharge safely to system ground. In order for the ESD protection to function effectively, the power supply and ground pins of the LT1237 must be connected to ground through low impedances. The power supply decoupling capacitors and charge pump storage capacitors provide this low impedance in normal application of the circuit. The only constraint is that low ESR capacitors must be used for bypassing and charge storage. ESD testing must be done with pins VCC, VL, V +, V – and GND shorted to ground or connected with low ESR capacitors. 6 ESD Test Circuit 1 V+ 5V VCC 2 1µF 3 26 0.2µF 4 25 5 24 6 23 7 22 8 21 9 20 10 19 11 18 12 17 13 16 14 15 RX1 IN DRIVER 2 OUT RX2 IN RX3 IN RX4 IN DRIVER 3 OUT RX5 IN (LOW-Q) ON/OFF V– 27 0.1µF DRIVER 1 OUT RS232 LINE PINS PROTECTED TO ±10kV 28 LT1237 0.1µF 0.2µF DRIVER 1 IN RX1 OUT DRIVER 2 IN RX2 OUT RX3 OUT RX4 OUT DRIVER 3 IN RX5 OUT (LOW-Q) GND DRIVER DISABLE 1237 TC01 LT1237 W U U UO APPLICATI S I FOR ATIO Storage Capacitor Selection The V + and V – storage capacitors must be chosen carefully to insure low ripple and stable operation. The LT1237 charge pump operates in a power efficient Burst ModeTM operation. When storage capacitor voltage drops below a preset threshold, the oscillator is gated on until V+ and V – are boosted up to levels exceeding a second threshold. The oscillator then turns off, and current is supplied from the V+ and V – storage capacitors. The V – potential is monitored to control charge pump operation. It is therefore important to insure lower V + ripple than V – ripple, or erratic operation of the charge pump will result. Proper operation is insured in most applications by choosing the V+ filter capacitor to be at least 5 times the V – filter capacitor value. If V + is more heavily loaded than V –, a larger ratio may be needed. The V – filter capacitor should be selected to obtain low ripple when the drivers are loaded, forcing the charge pump into continuous mode. A minimum value 0.1µF is suggested. U PACKAGE DESCRIPTIO Do not attempt to reduce V – ripple when the charge pump is in discontinuous Burst Mode operation. The ripple in this mode is determined by internal comparator thresholds. Larger storage capacitor values increase the burst period, and do not reduce ripple amplitude. Power Saving Operational Modes The LT1237 has both shutdown and driver disable operating modes. These operating modes can optimize power consumption based upon applications needs. The On/Off shutdown control turns off all circuitry except for Low-Q RX5. When RX5 detects a signal, this information can be used to wake up the system for full operation. If more than one line must be monitored, the driver disable mode provides a power efficient operating option. The driver disable mode turns off the charge pump and RS232 drivers, but keeps all five receivers active. Power consumption in driver disable mode is 3mA from VCC. Burst Mode is a trademark of Linear Technology Corporation Dimensions in inches (millimeters) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 0.205 – 0.212** (5.20 – 5.38) 0.397 – 0.407* (10.07 – 10.33) 0.068 – 0.078 (1.73 – 1.99) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 0° – 8° 0.0256 (0.65) BSC 0.010 – 0.015 (0.25 – 0.38) 0.005 – 0.009 0.022 – 0.037 (0.13 – 0.22) (0.55 – 0.95) 0.301 – 0.311 (7.65 – 7.90) 0.002 – 0.008 (0.05 – 0.21) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 G28 SSOP 0694 NW Package 28-Lead PDIP (Wide 0.600) (LTC DWG # 05-08-1520) 0.600 – 0.625 (15.240 – 15.875) 0.150 ± 0.005 (3.810 ± 0.127) 0.070 (1.778) TYP 0.045 – 0.065 (1.143 – 1.651) 1.455* (36.957) MAX 28 27 26 25 24 23 22 21 20 19 18 17 16 1 2 3 4 5 6 7 8 9 10 11 12 13 0.015 (0.381) MIN 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.625 –0.015 15.87 +0.889 –0.381 ) 15 0.505 – 0.560* (12.827 – 14.224) 0.125 (3.175) MIN 0.035 – 0.080 (0.889 – 2.032) 0.100 ± 0.010 (2.540 ± 0.254) 0.018 ± 0.003 (0.457 ± 0.076) 14 N28 1197 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 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. 7 LT1237 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. SW Package 28-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.291 – 0.299** (7.391 – 7.595) 0.037 – 0.045 (0.940 – 1.143) 0.010 – 0.029 × 45° 0.093 – 0.104 (2.362 – 2.642) (0.254 – 0.737) 0.697 – 0.712* (17.70 – 18.08) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) 0.050 (1.270) TYP 0.014 – 0.019 (0.356 – 0.482) TYP NOTE 1 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0.004 – 0.012 (0.102 – 0.305) 0.016 – 0.050 (0.406 – 1.270) NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 S28 (WIDE) 0996 *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 UO TYPICAL APPLICATI Typical Mouse Driving Application V+ 1.0µF 5V VCC MOUSE 2 × 0.1µF (1) OPTICS (5) (9) V– 27 3 26 4 25 DRIVER 1 IN 5 24 RX1 OUT DCD RX1 IN 6 23 DRIVER 2 IN DSR DRIVER 2 OUT 7 22 RX2 OUT RX RX2 IN 8 21 RX3 OUT RTS RX3 IN 9 20 RX4 OUT TX V– 2 28 LT1237 DRIVER 1 OUT V+ LOGIC 1 RX4 IN 10 CTS DRIVER 3 OUT 11 DTR RX5 IN (LOW-Q) 12 RI ON/OFF 13 14 DB9 0.1µF 2 × 0.1µF 19 DRIVER 3 IN LOGIC “0” LOGIC “0” MOUSE DATA LOGIC “1” 18 RX5 OUT (LOW-Q) 17 GND 16 DRIVER DISABLE 15 1237 TA03 RELATED PARTS PART NUMBER LTC®485 LT1137A LTC1387 LT1780/LT1781 LT1785/LT1791 8 DESCRIPTION Low Power RS485 Transceiver 3Dx/5Rx RS232 Transceiver RS232/RS485 Multiprotocol Transceiver 2Dx/2Rx RS232 Transceiver 60V Fault Tolerant RS485 Transceiver Linear Technology Corporation COMMENTS 15kV ESD 15kV ESD 15kV ESD 1237fa LT/TP 0799 2K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1992