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

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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,.

1 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 Current in Shutdown Pin Compatible with LT37A kbaud Operation for, C L = pf kbaud Operation for, C L = pf Operates to kbaud CMOS Comparable Low Power 3mW Operates from a Single V 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 APPLICATIO S Notebook Computers Palmtop Computers DESCRIPTIO The LT 37 is an advanced low power three driver, five receiver RS3 transceiver. Included on the chip is a shutdown pin for reducing supply current near zero. During shutdown one receiver remains active to detect incoming RS3 signals, for example, to wake up a system. The LT37 is fully compliant with all EIA RS3 specifications. New ESD structures on the chip allow the LT37 to survive multiple ±kv strikes, eliminating the need for costly TransZorbs on the RS3 line pins. The LT37 operates in excess of kbaud 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 RS3 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 TYPICAL APPLICATIO Output Waveforms.µF.µF TO LINE V + V V CC DRIVER OT RX IN DRIVER OT RX IN RX3 IN RX IN DRIVER 3 OT RX IN (LOW-Q) ON/OFF LT V.µF DRIVER IN RX OT DRIVER IN RX OT RX3 OT RX OT DRIVER 3 IN RX OT (LOW-Q) GND DRIVER DISABLE TO LOGIC.µF RING DETECT IN µcontroller OR µprocessor SHTDOWN CONTROL OT RECEIVER OTPT C L = pf DRIVER OTPT C L = pf R INPT 37 TA LT37 TA

2 ABSOLTE AXI RATI GS (Note ) W W W Supply Voltage (V CC )... V V V V... 3.V Input Voltage Driver... V to V + Receiver... 3V to 3V Output Voltage Driver... 3V to 3V Receiver....3V to V CC +.3V Short Circuit Duration V sec V... 3 sec Driver Output... Indefinite Receiver Output... Indefinite Operating Temperature Range LT37C... C to 7 C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... 3 C PACKAGE/ORDER I FOR V + V V CC C + 3 C DR OT RX IN DR OT 7 RX IN RX3 IN 9 RX IN DR3 OT RX IN (LOW-Q) ON/OFF 3 NC TOP VIEW G PACKAGE -LEAD PLASTIC SSOP W V 7 C C + DR IN RX OT 3 DR IN RX OT RX3 OT RX OT 9 DR3 IN RX OT (LOW-Q) 7 GND DRIVER DISABLE NC NW PACKAGE -LEAD (WIDE) PDIP SW PACKAGE -LEAD (WIDE) PLASTIC SO T JMAX = C, θ JA = 9 C/ W (G) T JMAX = C, θ JA = C/ W (NW) T JMAX = C, θ JA = C/ W (SW) ATIO ORDER PART NMBER LT37CG LT37CNW LT37CSW 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 T A = C. (Note ) PARAMETER CONDITIONS MIN TYP MAX NITS Power Supply Generator V + Output 7.9 V V Output 7 V Supply Current (V CC ) T A = C (Note 3) ma ma Supply Current when OFF (V CC ) Shutdown (Note ).. ma Driver Disable 3. ma Supply Rise Time C = C =.µf, ms Shutdown to Turn-On C + =.µf, C =.µf ON/OFF Pin Thresholds Input Low Level (Drivers Enabled).. V Input High Level (Drivers Disabled).. V ON/OFF Pin Current V V ON/OFF V µa DRIVER DISABLE Pin Thresholds Input Low Level (Drivers Enabled).. V Input High Level (Drivers Disabled).. V DRIVER DISABLE Pin Current V V DRIVER DISABLE V µa Oscillator Frequency Driver Outputs Loaded 3 khz

3 ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are at T A = C. (Note ) LT37 PARAMETER CONDITIONS MIN TYP MAX NITS 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).. V Input High Level (V OT = Low).. V Logic Input Current.V V IN V µa Output Short-Circuit Current V OT = V ±9 7 ma Output Leakage Current Shutdown V OT = ±3V (Note ) µa Data Rate (Note 7), C L = pf kbaud, C L = pf kbaud Slew Rate, C L = pf 3 V/µs, C L = pf 7 V/µs Propagation Delay Output Transition t HL High to Low (Note )..3 µs Output Transition t LH Low to High..3 µs Any Receiver Input Voltage Thresholds Input Low Threshold (V OT = High)..3 V Input High Threshold (V OT = Low).7. V Hysteresis... V Input Resistance V IN = ±V 3 7 kω Output Leakage Current Shutdown (Note ) V OT V CC µa Receivers,, 3, Output Voltage Output Low, I OT =.ma.. V Output High, I OT = µa (V CC = V) 3.. V Output Short-Circuit Current Sinking Current, V OT = V CC ma Sourcing Current, V OT = V ma Propagation Delay Output Transition t HL High to Low (Note ) ns Output Transition t LH Low to High 3 ns Receiver (LOW I SPPLY RX) Output Voltage Output Low, I OT = µa.. V Output High, I OT = µa (V CC = V) 3.. V Output Short-Circuit Current Sinking Current, V OT = V CC ma Sourcing Current, V OT = V ma Propagation Delay Output Transition t HL High to Low (Note ). 3 µs Output Transition t LH Low to High. 3 µs Note : Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note : Testing done at V CC = V and V ON/OFF = 3V, unless otherwise specified. Note 3: Supply current is measured as the average over several charge pump burst cycles. C + =.µf, C =.µf, C = C =.µf. All outputs are open, with all driver inputs tied high. Note : Measurements in shutdown are performed with V ON/OFF.V. Supply current measurements using driver disable are performed with V DRIVER DISABLE 3V. Note : For driver delay measurements, and C L = pf. Trigger points are set between the driver s input logic threshold and the output transition to the zero crossing (t HL =.V to V and t LH =.V to V). Note : For receiver delay measurements, C L = pf. Trigger points are set between the receiver s input logic threshold and the output transition to standard TTL/CMOS logic threshold (t HL =.3V to.v and t LH =.7V to.v). Note 7: Data rate operation guaranteed by slew rate, short-circuit current and propagation delay tests. 3

4 TYPICAL PERFOR A W CE CHARACTERISTICS DRIVER OTPT VOLTAGE (V) Driver Output Voltage OTPT HIGH OTPT LOW V CC = V V CC =.V V CC =.V V CC = V THRESHOLD VOLTAGE (V) Receiver Input Thresholds INPT HIGH INPT LOW SPPLY CRRENT (ma) 7 3 Supply Current vs Data Rate 3 DRIVERS ACTIVE C L = pf 7 TEMPERATRE ( C). 7 TEMPERATRE ( C) 7 DATA RATE (kbad) 37 G 37 G 37 G3 Supply Current in Shutdown Supply Current in Driver Disable 3. DRIVER DISABLE Threshold SPPLY CRRENT (µa) 7 SPPLY CRRENT (ma) 3 THRESHOLD VOLTAGE (V) TEMPERATRE ( C) 7 TEMPERATRE ( C) 7 TEMPERATRE ( C) 37 G 37 G 37 G 3. ON/OFF Thresholds Supply Current Driver Leakage in Shutdown THRESHOLD VOLTAGE (V)..... ON THRESHOLD OFF THRESHOLD SPPLY CRRENT (ma) DRIVERS LOADED DRIVER LOADED NO LOAD LEAKAGE CRRENT (µa) V OT = 3V V OT = 3V 7 TEMPERATRE ( C) 7 TEMPERATRE ( C). 7 TEMPERATRE ( C) 37 G7 37 G 37 G9

TYPICAL PERFOR 3 A W CE Driver Short-Circuit Current CHARACTERISTICS Receiver Short-Circuit Current SHORT-CIRCIT CRRENT (ma) I SC + I SC SHORT-CIRCIT CRRENT (ma) 3 RX TO RX I SC + RX I SC RX I SC +

37 G3 PI F CTIO S V CC : V Input Supply Pin. This pin should be decoupled with a.µf ceramic capacitor close to the package pin.

5 TYPICAL PERFOR 3 A W CE Driver Short-Circuit Current CHARACTERISTICS Receiver Short-Circuit Current SHORT-CIRCIT CRRENT (ma) I SC + I SC SHORT-CIRCIT CRRENT (ma) 3 RX TO RX I SC + RX I SC RX I SC + RX TO RX I SC 7 TEMPERATRE ( C) 7 TEMPERATRE ( C) 37 G 37 G Receiver Output Waveforms Driver Output Waveforms RX OTPT C L = pf RX TO RX OTPT C L = pf DRIVER OTPT C L = pf DRIVER OTPT INPT INPT 37 G 37 G3 PI F CTIO S V CC : V Input Supply Pin. This pin should be decoupled with a.µf 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 (RX, RX, RX3, and RX) assume a high impedance output state in shutdown. Only receiver RX remains active while the transceiver is in shutdown. The transceiver consumes only µa 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 RS3 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 (RS3 Drivers). V + V CC.V. This pin requires an external charge storage capacitor C.µF, tied to ground or V CC. Larger value capacitors may be used to reduce supply ripple. The ratio of the capacitors on V + and V should be greater than to. V : Negative Supply Output (RS3 Drivers). V (V CC.V). This pin requires an external charge storage capacitor C.µF. See the Applications Information section for guidance in choosing filter capacitors for V + and V.

6 PI F CTIO S C +, C, C +, C : Commutating Capacitor Inputs, require two external capacitors C.µF: one from C + to C, and another from C + to C. The capacitor s effective series resistance should be less than Ω. For C µf, 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: RS3 Driver Input Pins. These inputs are TTL/CMOS compatible. Inputs should not be allowed to float. Tie unused inputs to V CC. DRIVER OT: Driver Outputs at RS3 Voltage Levels. Driver output swing meets RS3 levels for loads up to 3k. Slew rates are controlled for lightly loaded lines. Output current capability is sufficient for load conditions up to pf. 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 + 3V to V + 3V. 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, ±kv for IEC -- contact mode discharges and ±kv for IEC -- air gap discharges. RX IN: Receiver Inputs. These pins accept RS3 level signals (±3V) into a protected k terminating resistor. The receiver inputs are protected against ESD to ±kv for human body model discharges, ±kv for IEC -- contact mode discharges and ±kv for IEC -- air gap 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 RX, RX, RX3, and RX are in a high impedance state when in shutdown mode to allow data line sharing. Outputs, including LOW-Q RX OT, are fully short-circuit protected to ground or V CC with the power on, off, or in shutdown mode. LOW Q-CRRENT RX IN: Low Power Receiver Input. This special receiver remains active when the part is in shutdown mode, consuming typically µa. This receiver has the same k input impedance and ±kv ESD protection characteristics as the other receivers. LOW Q-CRRENT RX OT: Low Power Receiver Output. This pin produces the same TTL/CMOS output voltage levels as receivers RX, RX, RX3, and RX with slightly decreased speed and short-circuit current. Data rates to kbaud are supported by this receiver. ESD PROTECTIO The RS3 line inputs of the LT37 have on-chip protection from ESD transients up to ±kv for human body discharges, ±kv for IEC -- contact mode discharges and ±V for IEC -- 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 LT37 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 L, V +, V and GND shorted to ground or connected with low ESR capacitors. µf RS3 LINE PINS PROTECTED TO ±kv ESD Test Circuit V + V V CC LT37.µF 3.µF DRIVER OT RX IN DRIVER OT 7 RX IN RX3 IN 9 RX IN DRIVER 3 OT RX IN (LOW-Q) ON/OFF V.µF.µF DRIVER IN RX OT DRIVER IN RX OT RX3 OT RX OT DRIVER 3 IN RX OT (LOW-Q) GND DRIVER DISABLE 37 TC

7 APPLICATI O S I FOR W ATIO Storage Capacitor Selection The V + and V storage capacitors must be chosen carefully to insure low ripple and stable operation. The LT37 charge pump operates in a power efficient Burst Mode TM 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 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.µf is suggested. LT37 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 LT37 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 RX. When RX 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 RS3 drivers, but keeps all five receivers active. Power consumption in driver disable mode is 3mA from V CC. Burst Mode is a trademark of Linear Technology Corporation PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted...** (..3) G Package -Lead Plastic SSOP (.9) (LTC DWG # --)..7 (.73.99).397.7* (.7.33) (.3.)..37 (..9). (.) BSC.. (..3).. (..).3.3 (7. 7.9) * DIMENSIONS DO NOT INCLDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED." (.mm) PER SIDE ** DIMENSIONS DO NOT INCLDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED." (.mm) PER SIDE G SSOP 9.. (..7).9. (.9.3) ( ). ±. (3. ±.7). (.3) MIN. (3.7) MIN.3. (.9.3). ±. (. ±.) *THESE DIMENSIONS DO NOT INCLDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. INCH (.mm).. (.3.) NW Package -Lead PDIP (Wide.) (LTC DWG # --). ±.3 (.7 ±.7).7 (.77) TYP..* (.7.) 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..* (3.97) MAX N 97 7

8 PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. SW Package -Lead Plastic Small Outline (Wide.3) (LTC DWG # --).9.99** ( ) (..737) (.3.).37. (.9.3).97.7* (7.7.) TYP.9.3 (.9.33) NOTE.. (..7). (.7) TYP..9 (.3.) TYP NOTE:. PIN 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 * DIMENSION DOES NOT INCLDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED." (.mm) PER SIDE ** DIMENSION DOES NOT INCLDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED." (.mm) PER SIDE NOTE.. (..3) (.7.3) S (WIDE) 99 TYPICAL APPLICATI O Typical Mouse Driving Application MOSE V + LOGIC OPTICS V () () (9) DCD DSR RX RTS TX CTS DTR RI V +.µf V V CC.µF DRIVER OT RX IN DRIVER OT RX IN RX3 IN RX IN DRIVER 3 OT RX IN (LOW-Q) ON/OFF LT V.µF.µF DRIVER IN RX OT DRIVER IN RX OT RX3 OT RX OT DRIVER 3 IN RX OT (LOW-Q) GND DRIVER DISABLE LOGIC LOGIC MOSE DATA LOGIC DB9 37 TA3 RELATED PARTS PART NMBER DESCRIPTION COMMENTS LTC Low Power RS Transceiver LT37A 3Dx/Rx RS3 Transceiver kv ESD LTC37 RS3/RS Multiprotocol Transceiver LT7/LT7 Dx/Rx RS3 Transceiver kv ESD LT7/LT79 V Fault Tolerant RS Transceiver kv ESD Linear Technology Corporation 3 McCarthy Blvd., Milpitas, CA () 3-9 FAX: () fa LT/TP 799 K REV A PRINTED IN SA LINEAR TECHNOLOGY CORPORATION 99

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

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