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| LT1381 Low Power 5V RS232 Dual Driver/Receiver with 0.1F Capacitors FEATURES s s s s s s s s s DESCRIPTIO s s ESD Protection over 10kV Low Cost Uses Small Capacitors: 0.1F CMOS Comparable Low Power: 40mW Operates from a Single 5V Supply 120kBaud Operation for RL = 3k, CL = 2500pF 250kBaud Operation for RL = 3k, CL = 1000pF Rugged Bipolar Design Outputs Assume a High Impedance State When Powered Down Absolutely No Latch-Up Available in Narrow SO Package APPLICATI s s s s s S Portable Computers Battery-Powered Systems Power Supply Generator Terminals Modems The LT1381 is a dual RS232 driver/receiver pair with integral charge pump to generate RS232 voltage levels from a single 5V supply. The circuit features rugged bipolar design to provide operating fault tolerance and ESD protection unmatched by competing CMOS designs. Using only 0.1F external capacitors, the circuit consumes only 40mW of power and can operate to 120k baud even while driving heavy capacitive loads. New ESD structures on the chip allow the LT1381 to survive multiple 10kV strikes, eliminating the need for costly TransZorbs(R) on the RS232 line pins. Driver outputs are protected from overload and can be shorted to ground or up to 25V without damage. During power-off conditions, driver and receiver outputs are in a high impedance state, allowing line sharing. TransZorb(R) is a registered trademark of General Instruments, GSI TYPICAL APPLICATI + 0.1F 1 3 LT1381 16 2 5V INPUT + 0.1F 6 0.1F V + OUT + 0.1F 4 5 11 V - OUT DRIVER OUTPUT RL = 3k CL = 2500pF 14 RS232 OUTPUT LOGIC INPUTS RECEIVER R OUTPUT CL = 50pF 10 12 7 13 5k RS232 OUTPUT RS232 INPUT INPUT LOGIC OUTPUTS 9 8 5k 15 RS232 INPUT LT1381 * TA01 U Output Waveforms LT1381 * TA02 + UO UO 1 LT1381 ABSOLUTE (Note 1) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW C1+ V+ C1 - C2+ C2 - V- TR2 OUT REC2 IN 1 2 3 4 5 6 7 8 16 VCC 15 GND 14 TR1 OUT 13 REC1 IN 12 REC1 OUT 11 TR1 IN 10 TR2 IN 9 REC2 OUT Supply Voltage (VCC) ................................................ 6V V + ........................................................................ 13.2V V - ...................................................................... -13.2V Input Voltage Driver ........................................................... V - to V + Receiver ............................................... - 30V to 30V ON/OFF ................................................. - 0.3V to 12V Output Voltage Driver ...................................... V+ - 30V to V - + 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 LT1381C ................................................. 0C to 70C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C ORDER PART NUMBER LT1381CN LT1381CS S PACKAGE N PACKAGE 16-LEAD PLASTIC DIP 16-LEAD PLASTIC SOIC TJMAX = 125C, JA = 90C/ W, JC = 46C/W (N) TJMAX = 125C, JA = 110C/ W, JC = 34C/W (S) Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS PARAMETER Power Supply Generator V + Output V - Output Supply Current (VCC) Supply Rise Time Oscillator Frequency Driver Output Voltage Swing Logic Input Voltage Level Logic Input Current Output Short-Circuit Current Output Leakage Current Data Rate Slew Rate Propagation Delay CONDITIONS (Note 2) MIN TYP 7.9 - 7.0 8 q MAX UNITS V V mA mA ms kHz V V V V A mA A kBaud kBaud V/s V/s s s (Note 3), TA = 25C C1 = C2 = C3 = C4 = 0.1F 14 16 0.2 130 Positive Negative q q q q q Load = 3k to GND Input Low Level (VOUT = High) Input High Level (VOUT = Low) 0.8V VIN 2.0V VOUT = 0V Power Off VOUT = 15V RL = 3k, CL = 2500pF RL = 3k, CL = 1000pF RL = 3k, CL = 51pF RL = 3k, CL = 2500pF Output Transition tHL High to Low (Note 4) Output Transition tLH Low to High 5.0 2.0 9 7.5 - 6.3 1.4 1.4 5 17 10 - 5.0 0.8 20 100 q 120 250 4 15 6 0.6 0.5 30 1.3 1.3 2 U W U U WW W LT1381 ELECTRICAL CHARACTERISTICS PARAMETER Receiver Input Voltage Thresholds Hysteresis Input Resistance Output Voltage Output Short-Circuit Current Propagation Delay VIN = 10V CONDITIONS (Note 2) MIN 0.8 q TYP 1.3 1.7 0.4 5 0.2 4.2 - 20 20 250 350 MAX UNITS V V V k V V mA mA ns ns Input Low Threshold (VOUT = High) Input High Threshold (VOUT = Low) 2.4 1.0 7 0.4 - 10 600 600 0.1 3 Output Low, IOUT = - 1.6mA Output High, IOUT = 160A (VCC = 5V) Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Output Transition tHL High-to-Low (Note 5) Output Transition tLH Low-to-High q q 3.5 10 The q denotes specifications which apply over the full operating temperature range. 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, unless otherwise specified. Note 3: Supply current is measured as the average over several charge pump cycles. C + = C - = C1 = C2 = 0.1F. All outputs are open, with all driver inputs tied high. Note 4: 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 5: 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). TYPICAL PERFOR A CE CHARACTERISTICS Driver Maximum Output Voltage vs Load Capacitance 9.0 2 DRIVERS LOADED 8.5 8.0 7.5 20k BAUD 7.0 6.5 6.0 5.5 120k BAUD 5.0 0 1 2 345678 LOAD CAPACITANCE (nF) 9 10 60k BAUD DRIVER OUTPUT VOLTAGE (V) PEAK OUTPUT VOLTAGE (V) PEAK OUTPUT VOLTAGE (V) UW LT1381 * TPC01 Driver Minimum Output Voltage vs Load Capacitance -4.0 2 DRIVERS LOADED -4.5 -5.0 60k BAUD -5.5 -6.0 -6.5 -7.0 0 1 2 345678 LOAD CAPACITANCE (nF) 9 10 120k BAUD 10 8 6 4 2 0 -2 -4 -6 -8 Driver Output Voltage RL = 3k VCC = 5.5V VCC = 5V VCC = 4.5V OUTPUT HIGH OUTPUT LOW VCC = 4.5V VCC = 5V VCC = 5.5V 20k BAUD -10 -55 -25 50 25 0 75 TEMPERATURE (C) 100 125 LT1381 * TPC02 LT1381 * TPC03 3 LT1381 TYPICAL PERFOR A CE CHARACTERISTICS Receiver Input Threshold 3.00 2.75 THRESHOLD VOLTAGE (V) 2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 -55 -25 50 25 0 75 TEMPERATURE (C) 100 125 INPUT LOW INPUT HIGH LEAKAGE CURRENT ( A) SUPPLY CURRENT (mA) Receiver Short-Circuit Current 50 ISC - 30 SHORT-CIRCUIT CURRENT (mA) SHORT-CIRCUIT CURRENT (mA) 40 20 15 10 5 0 -55 -25 30 ISC + 20 SLEW RATE (V/s) 10 0 -55 -25 50 25 0 75 TEMPERATURE (C) LTLT1381 * TPC07 V + Compliance Curve 10 V + (1F) 8 V + (0.1F) V + (V) V - (V) -8 -10 6 4 2 0 0 5 10 LOAD CURRENT + (mA) 4 UW LT1381 * TPC04 Supply Current vs Data Rate 50 2 DRIVERS ACTIVE RL = 3k CL = 2500pF 100 Driver Leakage in Shutdown 40 10 30 20 1 VOUT = 30V VOUT = -30V 10 0 0 25 50 75 100 DATA RATE (kBaud) 125 150 0.1 -55 -25 50 25 0 75 TEMPERATURE (C) 100 125 LT1381 * TPC05 LT1381 * TPC06 Driver Short-Circuit Current 20 18 25 ISC + Slew Rate vs Load Capacitance 16 14 12 10 8 6 4 2 -SLEW RATE +SLEW RATE ISC - 100 125 50 25 75 0 TEMPERATURE (C) 100 125 0 0 1 3 2 CAPACITANCE (nF) 4 5 LT1381 * TPC08 LT1381 * TPC09 V - Compliance Curve V - (1F) -6 V - (0.1F) -4 -2 0 15 LT1381 * TPC10 0 5 10 LOAD CURRENT - (mA) 15 LT1381 * TPC11 LT1381 PI FU CTIO S VCC: 5V Input Supply Pin. This pin should be decoupled with a 0.1F 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. V +: Positive Supply Output (RS232 Drivers). V + 2VCC - 1.5V. This pin requires an external charge storage capacitor C 0.1F, tied to ground or VCC. Larger value capacitors may be used to reduce supply ripple. With multiple transceivers, the V+ and V - pins may be paralleled into common capacitors. V -: Negative Supply Output (RS232 Drivers). V - -(2VCC - 2.5V). This pin requires an external charge storage capacitor C 0.1F. Larger value capacitors may be used to reduce supply ripple. With multiple transceivers, the V+ and V - pins may be paralleled into common capacitors. TR1 IN, TR2 IN: RS232 Driver Input Pins. These inputs are TTL/CMOS compatible. Inputs should not be allowed to float. Tie unused inputs to VCC. TR1 OUT, TR2 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 VCC = 0V. Outputs are fully short-circuit protected from V - + 25V to V + - 25V. 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 10kV for human body model discharges. REC1 IN, REC2 IN: Receiver Inputs. These pins accept RS232 level signals (30V) into a protected 5k terminating resistor. The receiver inputs are protected against ESD to 10kV for human body model discharges. Each receiver provides 0.4V of hysteresis for noise immunity. Open receiver inputs assume a logic low state. REC1 OUT, REC2 OUT: Receiver Outputs with TTL/CMOS Voltage Levels. Outputs are fully short-circuit protected to ground or VCC with the power ON or OFF. C1 +, C1 -, C2 +, C2 -: Commutating Capacitor Inputs. These pins require two external capacitors C 0.1F: one from C1+ to C1- and another from C2+ to C2 -. C1 may be deleted if a separate 12V supply is available and connected to pin C1+. ESD PROTECTIO The RS232 line inputs of the LT1381 have on-chip protection from ESD transients up to 10kV. 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 circuit 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, V +, V - and GND shorted to ground or connected with low ESR capacitors. U U U U ESD Test Circuit C1+ 1 16 5V VCC LT1381 15 GND 14 13 12 11 10 9 DR1 OUT RX1 IN RX1 OUT DR1 IN DR2 IN RX2 OUT RS232 LINE PINS PROTECTED TO 10kV + 0.1F 0.1F + V+ 2 C1- 3 C2+ + 0.1F + 0.1F 0.1F 4 C2 - 5 + V- 6 7 8 DR2 OUT RS232 LINE PINS PROTECTED TO 10kV RX2 IN LT1381 * ESD TC 5 LT1381 TYPICAL APPLICATIO S Isolated RS232 Driver/Receiver VIN = 5V 10% FROM SYSTEM 47 CTX20-1 1:1 1N5818 1 LT1121-5 5V 10% + 100F ILIM VIN SW1 LT1111 FB GND SW2 ISOLATOR OUTPUT (DATA TO SYSTEM) VOUT VCC OS LTC1145 GND2 GND1 IN ISOLATOR INPUT (DATA FROM SYSTEM) VIN VCC IN LTC1145 GND1 GND2 OS 9 RX 8 11 DX 14 15 LT1381 * TA03 SYSTEM GROUND ISOLATION BARRIER FLOATING GROUND Data Transmission Across Isolation Barrier ISOLATOR INPUT RS232 INPUT RS232 OUTPUT ISOLATOR OUTPUT 6 + U L1 20H 1N5818 + 100F 0.1F + 10F 13.7V 10k + 1F 1k 1 16 VCC LT1381 RS232 + 0.1F 3 4 2 + 0.1F + 0.1F 5 6 0.1F RS232 INPUT RS232 OUTPUT LT1381 TYPICAL APPLICATIO S Operation Using 5V and 12V Power Supplies 12V INPUT 1 2 16 3 11 LOGIC INPUTS 14 10 12 7 13 5k LOGIC OUTPUTS 9 8 5k 15 Sharing Capacitors 5V VCC 16 LT1381 11 V+ V- 2 6 14 + + RS232 OUTPUT 0.1F 0.1F TTL INPUT TTL INPUT TTL INPUT 10 7 RS232 OUTPUT TTL OUTPUT 12 5k 9 5k 1 C1+ C1- C2+ C2 - 13 RS232 INPUT TTL OUTPUT 8 RS232 INPUT 4 + 0.1F 3 + 0.1F 5 0.1F 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 circuits as described herein will not infringe on existing patent rights. + U 5V INPUT LT1381 + 0.1F 4 5 16 0.1F -12VOUT RS232 OUTPUT RS232 OUTPUT RS232 INPUT RS232 INPUT LT1381 * TA06 5V VCC 16 LT1381 11 V+ V- 2 6 14 RS232 OUTPUT TTL INPUT 10 7 RS232 OUTPUT TTL OUTPUT 12 5k 9 5k 1 C1+ C1- C2+ C2 - LT1381 * TA07 13 RS232 INPUT TTL OUTPUT 8 RS232 INPUT 4 + 3 + 0.1F 5 7 LT1381 PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead Plastic DIP 0.770 (19.558) MAX 16 15 14 13 12 11 10 9 0.260 0.010 (6.604 0.254) 1 0.300 - 0.325 (7.620 - 8.255) 0.130 0.005 (3.302 0.127) 2 3 4 5 6 7 8 0.045 - 0.065 (1.143 - 1.651) 0.009 - 0.015 (0.229 - 0.381) 0.015 (0.381) MIN 0.065 (1.651) TYP ( +0.025 0.325 -0.015 8.255 +0.635 -0.381 ) 0.125 (3.175) MIN 0.045 0.015 (1.143 0.381) 0.100 0.010 (2.540 0.254) 0.018 0.003 (0.457 0.076) N16 0393 S Package 16-Lead Plastic SOIC 0.386 - 0.394* (9.804 - 10.008) 16 15 14 13 12 11 10 9 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157* (3.810 - 3.988) 1 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0 - 8 TYP 0.053 - 0.069 (1.346 - 1.752) 2 3 4 5 6 7 8 0.004 - 0.010 (0.101 - 0.254) 0.016 - 0.050 0.406 - 1.270 0.014 - 0.019 (0.355 - 0.483) 0.050 (1.270) TYP S16 0393 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 LT/GP 0593 10K REV 0 (c) LINEAR TECHNOLOGY CORPORATION 1993 |
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