LT1537 Advanced Low Power 5V RS232 Transceiver with Small Capacitors U S DESCRIPTIO

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Anissa Kathleen Bryan
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1 Advanced Low Power V RS232 Transceiver with Small Capacitors FEATRES Low Cost ses Small Capacitors:,.2µF 1µA Supply Current in Shutdown 12kBaud Operation for, C L = 2pF 2kBaud Operation for, C L = 1pF CMOS Comparable Low Power: mw Operates from a Single V Supply Easy PC Layout: Flow-through Architecture Rugged Bipolar Design Outputs Assume a High Impedance State When Off or Powered Down Improved Protection: RS232 I/O Lines Can Be Forced to ±2V Without Damage Output Overvoltage Does Not Force Current Back into Supplies Absolutely No Latch-p Available in SO Package APPLICATI O S Notebook Computers Palmtop Computers DESCRIPTIO The LT 137 is a three-driver, five-receiver RS232 transceiver, pin compatible with the LT1137A, offering performance improvements and two shutdown modes. The LT137 s charge pump is designed for extended compliance and can deliver over 3mA of load current. Supply current is typically ma, competitive with similar CMOS devices. An advanced driver output stage operates up to 2kbaud while driving heavy capacitive loads. The LT137 is fully compliant with all RS232 specifications. Special bipolar construction techniques protect the drivers and receivers beyond the fault conditions stipulated for RS232. Driver outputs and receiver inputs can be shorted to ±2V without damaging the device or the power supply generator. In addition, the RS232 I/O pins are resilient to multiple ±kv ESD strikes. The transceiver has two shutdown modes. One mode disables the drivers and the charge pump, the other shuts down all circuitry. While shut down, the drivers and receivers assume high impedance output states., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATI 2 TO LINE V 1 V V CC 2 3 OT OT OT ON/OFF = V 13 1 LT137 O V IN RX OT IN RX OT RX OT RX OT IN RX OT GND DISABLE 2 TO R OTPT C L = pf OTPT C L = 2pF INPT Output Waveforms LT137 TA2 LT137 TA1 1

2 ABSOLTE AXI RATI GS W W W (Note 1) Supply Voltage (V CC )....V V V V (Note 7)....V Input Voltage Driver... V to V Receiver... 2V to 2V Output Voltage Driver... V 2V to V 2V Receiver....3V to V CC.3V Short Circuit Duration V... 3 sec V... 3 sec Driver Output... Indefinite Receiver Output... Indefinite Operating Temperature Range LT137C... C to 7 C Storage Temperature Range... C to 1 C Lead Temperature (Soldering, 1 sec)... 3 C PACKAGE/ORDER I FOR V 1 V V CC 2 C1 3 C1 OT OT OT ON/OFF 13 NC 1 G PACKAGE 2-LEAD PLASTIC SSOP TOP VIEW W 2 V 27 C2 2 C2 2 IN 2 RX OT 23 IN 22 RX OT 21 RX OT 2 RX OT 19 IN 1 RX OT 17 GND 1 DISABLE 1 NC SW PACKAGE 2-LEAD PLASTIC SO WIDE T JMAX = 1 C, θ JA = 9 C/ W (G) T JMAX = 1 C, θ JA = C/ W (SW) Consult factory for Industrial and Military grade parts. ATIO ORDER PART NMBER LT137CG LT137CSW ELECTRICAL CHARA CTERISTICS (Note 2) PARAMETER CONDITIONS MIN TYP MAX NITS Power Supply Generator V Output. V V Output 7. V Supply Current (V CC ) (Note 3) 17 ma Supply Current When OFF (V CC ) Shutdown (Note ) 1. 1 µa DISABLE 1. ma Shutdown to Turn-On C, C =, C1, C2 =.2µF.2 ms ON/OFF Pin Thresholds Input LOW Level (Device Shutdown) 1.. V Input HIGH Level (Device Enabled) V ON/OFF Pin Current V V ON/OFF V 1 µa Driver Disable Pin Thresholds Input LOW Level (Drivers Enabled) 1.. V Input HIGH Level (Drivers Disabled) V Driver Disable Pin Current V V DISABLE V 1 µa Oscillator Frequency 13 khz Any Driver Output Voltage Swing Load = 3k to GND Positive. 7. V Negative.3. V Logic Input Voltage Level Input LOW Level (V OT = HIGH) 1.. V Input HIGH Level (V OT = LOW) 2 1. Logic Input Current.V V IN 2V 2 µa Output Short-Circuit Current V OT = V ±17 ma 2

3 ELECTRICAL CHARA CTERISTICS (Note 2) PARAMETER CONDITIONS MIN TYP MAX NITS Any Driver Output Leakage Current Shutdown V OT = ±1V (Note ) 1 1 µa Data Rate, C L = 2pF 12 kbaud, C L = 1pF 2 kbaud Slew Rate, C L = 1pF 1 3 V/µs, C L = 2pF 1 V/µs Propagation Delay Output Transition t HL HIGH to LOW (Note ). 1.3 µs Output Transition t LH LOW to HIGH. 1.3 µs Any Receiver Input Voltage Thresholds Input LOW Threshold (V OT = HIGH). 1.3 V Input HIGH Threshold (V OT = LOW) V Hysteresis V Input Resistance V IN = ±1V 3 7 kω Output Voltage Output LOW, I OT = 1.mA.2. V Output HIGH, I OT = 1µA (V CC = V) 3..2 V Output Leakage Current Shutdown (Note ) V OT V CC 1 1 µa Output Short-Circuit Current Sinking Current, V OT = V CC 2 1 ma Sourcing Current, V OT = V 1 2 ma Propagation Delay Output Transition t HL HIGH to LOW (Note ) 2 ns Output Transition t LH LOW to HIGH 3 ns The denotes specifications which apply over the operating temperature range ( C T A 7 C for commercial grade and C T A C for industrial grade). Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Testing done at V CC = V and V ON/OFF = 3V. C1 = C2 =.2µF, C = C =. Note 3: Supply current is measured with driver and receiver outputs unloaded and the driver inputs tied high. Note : Supply current and leakage current measurements in shutdown are performed with V ON/OFF =.1V. Supply current measurements using DISABLE are performed with V DISABLE = 3V. Note : For driver delay measurements, and C L = 1pF. Trigger points are set between the driver s input logic threshold and the output transition to the zero crossing (t HL = 1.V to V and t LH = 1.V to V). Note : For receiver delay measurements, C L = 1pF. 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.V and t LH = 1.7V to.v). Note 7: Absolute maximum externally applied voltage. Internal charge pump may force a larger value on this pin. TYPICAL PERFOR OTPT VOLTAGE (V) A W CECHARA CTERISTICS Driver Output Voltage Receiver Input Thresholds Supply Current vs Data Rate V CC =.V V CC = V V CC =.V OTPT HIGH V CC = V OTPT LOW V CC =.V V CC =.V TEMPERATRE ( C) THRESHOLD VOLTAGE (V) INPT HIGH INPT LOW TEMPERATRE ( C) SPPLY CRRENT (ma) S ACTIVE C L = 2pF DATA RATE (kbad) 1 LT137 TPC1 ILT137 TPC2 LTX137 TPC3 3

4 TYPICAL PERFOR 1 Positive Supply Output Compliance Curve A W CE CHARA CTERISTICS 1 Negative Supply Output Compliance Curve 3. Driver Disable Threshold POSITIVE SPPLY OTPT (V) 2 NEGATIVE SPPLY OTPT (V) 2 THRESHOLD VOLTAGE (V) POSITIVE LOAD CRRENT (ma) 1 1 NEGATIVE LOAD CRRENT (ma) TEMPERATRE ( C) LT137 TPC LT137 TPC LT137 TPC THRESHOLD VOLTAGE (V) On/Off Thresholds ON THRESHOLD OFF THRESHOLD SPPLY VOLTAGE (ma) Supply Current 2kBAD S LOADED R 2 L = 3k 2 2 S LOADED 1 1 S LOADED 1 NO LOAD LEAKAGE CRRENT (µa) Driver Leakage in Shutdown 1 1 V OT = 1V 1 V OT = 1V TEMPERATRE ( C) TEMPERATRE ( C) TEMPERATRE ( C) LT137 TPC7 LT137 TPC LT137 TPC9 3 Driver Output Short-Circuit Current 3 Receiver Short-Circuit Current SHORT-CIRCIT CRRENT (ma) I SC I SC SHORT-CIRCIT CRRENT (ma) I SC I SC TEMPERATRE ( C) TEMPERATRE ( C) LT137 TPC1 LT137 TPC11

TYPICAL PERFOR A W Shutdown to Driver Output CECHARA CTERISTICS Driver Output Waveforms OTPT HIGH OTPT LOW ON/OFF PIN 1 1 OTPT OTPT C L = 2pF INPT LT137 TPC12 LT137 TPC13 PI F CTIO S V CC : V Input

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.

5 TYPICAL PERFOR A W Shutdown to Driver Output CECHARA CTERISTICS Driver Output Waveforms OTPT HIGH OTPT LOW ON/OFF PIN 1 1 OTPT OTPT C L = 2pF INPT LT137 TPC12 LT137 TPC13 PI F CTIO S V CC : V Input Supply Pin. Supply current drops to zero in the shutdown mode. This pin should be decoupled with a 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 shutdown mode which reduces input supply current to zero and places all of the drivers and receivers in high impedance state. A logic HIGH fully enables the transceiver. 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 drivers in a high impedance state. 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 1.mA when in DISABLE mode. V : Positive Supply Output (RS232 Drivers). V 2V CC 1.V. This pin requires an external charge storage capacitor C, tied to ground or V CC. Larger value capacitors may be used to reduce supply ripple. With multiple transceivers, the V and V pins may be paralleled into common capacitors. For large numbers of transceivers, increasing the size of the shared common storage capacitors is recommended to reduce ripple. V : Negative Supply Output (RS232 Drivers). V (2V CC 2.V). This pin requires an external charge storage capacitor C. V is short-circuit proof for 3 seconds. C1, C1, C2, C2 : Commutating Capacitor Inputs. These pins require two external capacitors C.2µF: one from C1 to C1 and another from C2 to C2. To maintain charge pump efficiency, the capacitor s effective series resistance should be less than 2Ω. Low ESR ceramic capacitors work well in this application. IN: RS232 Driver Input Pins. These inputs are TTL/CMOS compatible. Inputs should not be allowed to float. Tie unused inputs to V CC. OT: 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 2pF. Outputs are in a high impedance state when in shutdown mode, V CC = V or when the driver disable pin is active. Outputs are fully short-circuit protected from V 2V to V 2V. 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 ±kv for human body model discharges.

6 PI F CTIO S : Receiver Inputs. These pins accept RS232 level signals (± 2V) into a protected k terminating resistor. The receiver inputs are protected against ESD to ±kv for human body model discharges. Each receiver provides.v of hysteresis for noise immunity. Open receiver inputs assume a logic low state. RX OT: Receiver Outputs with TTL/CMOS Voltage Levels. Outputs are in a high impedance state when in shutdown mode to allow data line sharing. Outputs are fully short-circuit protected to ground or V CC with the power on, off, or in shutdown mode. ESD PROTECTIO The RS232 line inputs of the LT137 have on-chip protection from ESD transients up to ±kv during shutdown or power ON state. 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 LT137 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 V CC, V, V and GND shorted to ground or connected with low ESR capacitors. RS232 LINE PINS PROTECTED TO ±kv ESD Test Circuit V 1 V V CC 2 LT µF 1 OT RX1 IN 2 OT 7 RX2 IN RX3 IN OT ON/OFF V.2µF 1 IN RX1 OT 2 IN RX2 OT RX3 OT RX OT 3 IN RX OT GND DISABLE LT137 ESD TC TYPICAL APPLICATIO S LT137 Driving Remote Powered LTC V CC INPT OTPT ON/OFF = V V CC V.1V LT137 V LTC 132 RS232 OTPT THREE S NOT SED RS232 OTPT V V ON/OFF = V OTPT INPT LT137 TA3

7 TYPICAL APPLICATIO S Typical Mouse Driving Application MOSE V OPTICS V (1) () (9) DCD DSR RX RTS TX CTS DTR RI V 1 V V 2 CC OT RX1 IN 2 OT 7 RX2 IN RX3 IN OT ON/OFF = V 13 1 LT137 2 V IN 2 RX1 OT 23 2 IN 22 RX2 OT 21 RX3 OT MOSE DATA 2 RX OT 19 3 IN 1 1 RX OT 17 GND 1 DISABLE 1 DB9 LT1137A TA PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. G Package 2-Lead SSOP * ( ) * (.2.3)..7 ( ) (7. 7.9)..9 (.13.22) (..9).2 (.) BSC *THESE DIMENSIONS DO NOT INCLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. INCH (.1mm)..1.1 (.2.3).2. (..21) 2SSOP (.127) RAD MIN.9.13 ( ) ( ) (NOTE 2).1.29 (.2.737) NOTE 1.1. (. 1.27).93.1 ( ) TYP. (1.27) TYP.1.19 (.3.2) S Package 2-Lead Plastic SOL NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANFACTRING OPTIONS. THE PART MAY BE SPPLIED WITH OR WITHOT ANY OF THE OPTIONS..37. ( ) NOTE (.12.3) ( ) (NOTE 2) THESE DIMENSIONS DO NOT INCLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. INCH (.1mm). 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 ( ) SOL

8 RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT1137A V 3-Driver/-Receiver RS232 Transceiver with Shutdown Premium Performance pgrade to LT137 LT113A V -Driver/3-Receiver RS232 Transceiver Premium Performance DCE, Compliment to LT137 LT1237 V 3-Driver/-Receiver RS232 Transceiver with One Lower Power, Premium Performance pgrade to LT137 Receiver Active in Shutdown LT133 V 3-Driver/-Receiver RS232 Transceiver with 3V Premium Performance Device for V Systems with 3V Logic Supplies Logic Interface and Shutdown LT1331 V 3-Driver/-Receiver RS232 Transceiver with 3V LT133 with Low Power Receiver That Stays Active During Shutdown Logic Interface and Receiver Active in Shutdown LTC1337 ltra-low Power V 3-Driver/-Receiver RS232 ltra-low Power, Premium Performance pgrade to LT137 Transceiver with Shutdown LTC133 V -Driver/3-Receiver RS232 Transceiver with Shutdown ltra-low Power, Peripheral-Side Compliment to LT137 LT/GP 9 1K PRINTED IN SA Linear Technology Corporation 13 McCarthy Blvd., Milpitas, CA () FAX: () 3-7 TELEX: LINEAR TECHNOLOGY CORPORATION 199

LT1237 5V RS232 Transceiver with Advanced Power Management and One Receiver Active in Shutdown FEATURES TO LOGIC RING DETECT IN SHUTDOWN CONTROL OUT

LT1237 5V RS232 Transceiver with Advanced Power Management and One Receiver Active in Shutdown FEATURES TO LOGIC RING DETECT IN SHUTDOWN CONTROL OUT V RS3 Transceiver with Advanced Power Management and One Receiver Active in Shutdown FEATRES One Receiver Remains Active While in Shutdown ESD Protection over ±kv ses Small Capacitors:.µF,.µF,.µF µa Supply