Datasheet

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LTC1334

Single 5V RS232/RS485

Multiprotocol Transceiver

The LTC

1334 is a low power CMOS

bidirectional trans-

ceiver featuring two

reconfigurable interface ports. It can

be configured as two RS485 differential ports, as two dual

RS232 single-ended ports or as one RS485 differential

port and one dual RS232 single-ended port. An onboard

charge pump requires four 0.1µF capacitors to generate

boosted positive and negative supplies, allowing the RS232

drivers to meet the RS232 ±5V output swing requirement

with only a single 5V supply. A shutdown mode reduces

the I

supply current to 10µA.

The RS232 transceivers are in full compliance with RS232

specifications. The RS485 transceivers are in full compli-

ance with RS485 and RS422 specifications. All interface

drivers feature short-circuit and thermal shutdown pro-

tection. An enable pin allows RS485 driver outputs to be

forced into high impedance, which is maintained even

when the outputs are forced beyond supply rails or power

is off. Both driver outputs and receiver inputs feature

±10kV ESD protection. A loopback mode allows the driver

outputs to be connected back to the receiver inputs for

diagnostic self-test.

■

Four RS232 Transceivers or Two RS485

Transceivers on One Chip

■

Operates from a Single 5V Supply

■

Withstands Repeated ±10kV ESD Pulses

■

Uses Small Charge Pump Capacitors: 0.1µF

■

Low Supply Current: 8mA Typical

■

10µA Supply Current in Shutdown

■

Self-Testing Capability in Loopback Mode

■

Power-Up/Down Glitch-Free Outputs

■

Driver Maintains High Impedance in Three-State,

Shutdown or with Power Off

■

Thermal Shutdown Protection

■

Receiver Inputs Can Withstand ±25V

■

Low Power RS485/RS422/RS232/EIA562 Interface

■

Software-Selectable Multiprotocol Interface Port

■

Cable Repeaters

■

Level Translators

, LTC and LT are registered trademarks of Linear Technology Corporation.

2728

CC1

120Ω

LTC1334

LTC1334 • TA01

RX OUT

RS485 INTERFACE

DR ENABLE

DR IN

LTC1334

RX OUT

DR ENABLE

DR IN

120Ω

4000-FT 24-GAUGE TWISTED PAIR

DR IN

RX OUT

DR IN

RS232 INTERFACE

ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE

DR IN

RX OUT

DR IN

212827

CC2

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (16 pages)

PAGE 1
LTC1334 Single 5V RS232/RS485 Multiprotocol Transceiver U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC ®1334 is a low power CMOS bidirectional transceiver featuring two reconfigurable interface ports. It can be configured as two RS485 differential ports, as two dual RS232 single-ended ports or as one RS485 differential port and one dual RS232 single-ended port. An onboard charge pump requires four 0.
PAGE 2
LTC1334 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ............................................. 6.5V Input Voltage Drivers ................................... – 0.3V to (VCC + 0.3V) Receivers ............................................. – 25V to 25V ON/OFF, LB, SEL1, SEL2 ........ – 0.3V to (VCC + 0.3V) Output Voltage Drivers ................................................. – 18V to 18V Receivers ............................... – 0.
PAGE 3
LTC1334 DC ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 0.2 0.
PAGE 4
LTC1334 AC ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.
PAGE 5
LTC1334 U W TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output Current vs Output High Voltage 40 TA = 25°C VCC = 5V 18 2.0 TA = 25°C VCC = 5V 35 OUTPUT CURRENT (mA) 16 14 12 10 8 6 VCC = 5V INPUT THRESHOLD VOLTAGE (V) 20 OUTPUT CURRENT (mA) RS232 Receiver Input Threshold Voltage vs Temperature Receiver Output Current vs Output Low Voltage 30 25 20 15 10 4 5 2 0 0 2.0 2.5 3.5 4.0 3.0 OUTPUT VOLTAGE (V) 4.5 5.0 0 0.5 1.0 1.5 2.
PAGE 6
LTC1334 U W TYPICAL PERFORMANCE CHARACTERISTICS RS485 Driver Output Low Voltage vs Output Current RS485 Driver Output High Voltage vs Output Current 120 TA = 25°C VCC = 5V 100 OUTPUT CURRENT (mA) –70 160 TA = 25°C VCC = 5V –60 –50 –40 –30 –20 OUTPUT SHORT-CIRCUIT CURRENT (mA) –80 OUTPUT CURRENT (mA) RS485 Driver Output Short-Circuit Current vs Temperature 80 60 40 20 –10 0 0 1 0 2 3 OUTPUT VOLTAGE (V) 4 5 1 0 2 3 4 OUTPUT VOLTAGE (V) 10 OUTPUT VOLTAGE (V) 4 2 VCC = 5V RL = 3k –2
PAGE 7
LTC1334 U U U PI FU CTIO S RB2 (Pin 16): Receiver Output. RA2 (Pin 17): Receiver Output. DZ2/DE2 (Pin 18): RS232 Driver Input in RS232 Mode. RS485 Driver Enable with internal pull-up in RS485 mode. DY2 (Pin 19): Driver Input. ON/OFF (Pin 20): A high logic input enables the transceivers. A low puts the device into shutdown mode and reduces ICC to 10µA. This pin has an internal pull-up. LB (Pin 21): Loopback Control Input. A low logic level enables internal loopback connections.
PAGE 8
LTC1334 W BLOCK DIAGRA SM Interface Configuration with Loopback Disabled PORT 1 = RS232 MODE PORT 2 = RS232 MODE 1 28 C1 VDD A1 B1 Y1 Z1 SEL1 = 0V SEL2 = 0V Z2 Y2 B2 A2 GND 2 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 PORT 1 = RS485 MODE PORT 2 = RS232 MODE 1 28 C2 C1 VCC VDD A1 RB1 RA1 B1 DZ1 Y1 DY1 Z1 SEL1 = 5V 2 27 3 26 4 25 5 24 6 23 7 22 8 21 LB ON SEL2 = 0V DY2 Z2 DZ2 Y2 B2 RA2 RB2 A2 VEE GND 9 20 10 19 11 18 12
PAGE 9
LTC1334 TEST CIRCUITS VCC Z VOD D R 3V 3V R SEL Z B Y CL A S1 SEL R RL DE VOC CL 500Ω DR OUT 15pF CL S2 3V Y LTC1334 • F03 LTC1334 • F02 LTC1334 • F01 Figure 1. RS422/RS485 Driver Test Load Figure 2. RS485 Driver/Receiver Timing Test Circuit Figure 3. RS485 Driver Output Enable/Disable Timing Test Load 0V 0V 0V SEL D Y, Z SEL SEL Y, Z D A, B R RL CL VIN VOUT 15pF LTC1334 • F05 LTC1334 • F04 Figure 4. RS232 Driver Swing/Timing Test Circuit Figure 5.
PAGE 10
LTC1334 U W SWITCHI G WAVEFOR S 3V 1.5V DE f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 1.5V 0V tZL tLZ 5V Y, Z 2.3V OUTPUT NORMALLY LOW VOL tZH OUTPUT NORMALLY HIGH VOH 0.5V tHZ 0.5V 2.3V Z, Y 0V LTC1334 • F07 Figure 7. RS485 Driver Enable and Disable Times VOD2 0V B–A f = 1MHz: tr ≤ 10ns: tf ≤ 10ns INPUT 0V –VOD2 tPLH R tPHL OUTPUT VOH 1.5V 1.5V VOL LTC1334 • F08 Figure 8. RS485 Receiver Propagation Delays 3V 1.5V 1.5V D 0V tPHL tPLH VO Y, Z LTC1334 • F09 0V 0V –VO Figure 9.
PAGE 11
LTC1334 W U U UO APPLICATI S I FOR ATIO Basic Theory of Operation The LTC1334 has two interface ports. Each port may be configured as a pair of single-ended RS232 transceivers or as a differential RS485 transceiver by forcing the port’s selection input to a low or high, respectively. The LTC1334 provides two RS232 drivers and two RS232 receivers or one RS485 driver and one RS485 receiver per port. All the interface drivers feature three-state outputs.
PAGE 12
LTC1334 W U UO S I FOR ATIO 1 0.1µF C1 U APPLICATI VDD 0.1µF LTC1334 28 2 27 0.1µF 3 26 C2 VCC 5V 0.1µF 25 RX OUT 4 INPUT A K1A 120Ω PORT 1 INTERFACE 6 OUTPUT A 22 K1B 5V K1* TX2A-5V 24 5 INPUT B 8 120Ω 7 OUTPUT B 23 21 360k FMMT619** 20 RX OUT DR IN SEL1 Typical Applications DR IN/ENABLE LB A typical RS232/EIA562 interface application is shown in Figure 13 with the LTC1334. ON/OFF TERM1 7.
PAGE 13
LTC1334 W U U UO APPLICATI S I FOR ATIO port is configured as an RS232 transceiver and the other as an RS485 transceiver. A typical RS422 connection (Figure 15) allows one driver and ten receivers on a twisted pair of wires terminated with a 100Ω resistor at one end. Using two LTC1334s as level translators, the RS232/ EIA562 interface distance can be extended to 4000 feet with twisted-pair wires (Figure 18). A typical twisted-pair line repeater is shown in Figure 16.
PAGE 14
LTC1334 W U U UO APPLICATI S I FOR ATIO 1 LTC1323CS-16 1 0.33µF 2 TXD TXDEN SHDN RXEN RXDO 16 CHARGE PUMP 0.1µF 5V 15 3 14 4 13 0.1µF 0.33µF 1µF EMI 1k EMI 6 11 TXD + 7 10 RXD – 8 9 120Ω 120Ω 1k SEL1, 5V EMI SEL2, 5V 5Ω TO 22Ω FERRITE BEAD 5Ω TO 22Ω EMI = OR 100pF FERRITE BEAD OR 100pF 4 25 24 23 100pF NC 22 7 EMI EMI 26 1k EMI RXD + 3 6 EMI 1k 28 8 21 9 20 10 19 11 NC 12 NC 18 13 16 14 15 NC 0.
PAGE 15
LTC1334 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 10.07 – 10.33* (0.397 – 0.407) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 7.65 – 7.90 (0.301 – 0.311) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 5.20 – 5.38** (0.205 – 0.212) 1.73 – 1.99 (0.068 – 0.078) 0° – 8° 0.13 – 0.22 (0.005 – 0.009) 0.65 (0.0256) BSC 0.55 – 0.95 (0.022 – 0.037) NOTE: DIMENSIONS ARE IN MILLIMETERS *DIMENSIONS DO NOT INCLUDE MOLD FLASH.
PAGE 16
LTC1334 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. SW Package 28-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1690) 0.697 – 0.712* (17.70 – 18.08) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0.291 – 0.299** (7.391 – 7.595) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 0.037 – 0.045 (0.940 – 1.143) 0.093 – 0.104 (2.362 – 2.642) 0.010 – 0.029 × 45° (0.254 – 0.737) 0° – 8° TYP 0.009 – 0.013 (0.