Datasheet

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LTC1344A

Software-Selectable

Cable Terminator

Daisy-Chained Control Outputs

TYPICAL APPLICATION

DTE or DCE Multiprotocol Serial Interface with DB-25 Connector

D2 D1

LTC1544

RTS

DTRDSR DCDCTS

R2 R1R4

LTC1543

TXDSCTETXC

RXCRXD

21424111512179314192062322513 81018 7 16

1344A TA01

LTC1344A

R1R3

TXD A (103)

TXD B

SCTE A (113)

SCTE B

RXC A (115)

RXC B

RXD A (104)

RXD B

RTS A (105)

RTS B

DTR A (108)

DTR B

CTS A (106)

CTS B

LL A (141)

SG (102)

SHIELD (101)

DB-25 CONNECTOR

TXC A (114)

TXC B

DCD A (107)

DCD B

DSR A (109)

DSR B

■

Data Networking

■

CSU and DSU

■

Data Routers

APPLICATIONS

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

FEATURES

■

Software-Selectable Cable Termination for:

RS232 (V.28)

RS423 (V.10)

RS422 (V.11)

RS485

RS449

EIA530

EIA530-A

V.35

V.36

X.21

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Outputs Won’t Load the Line with Power Off

The LTC

1344A features six software-selectable

multiprotocol cable terminators. Each terminator can be

configured as an RS422 (V.11) 100Ω minimum differen-

tial load, V.35 T-network load or an open circuit for use

with RS232 (V.28) or RS423 (V.10) transceivers that

provide their own termination. When combined with the

LTC1543 and LTC1544, the LTC1344A forms a complete

software-selectable multiprotocol serial port. A data bus

latch feature allows sharing of the select lines between

multiple interface ports.

The LTC1344A is similar to the LTC1344 except for a

difference in the Mode Selection table.

The LTC1344A is available in a 24-lead SSOP.

DESCRIPTION

Summary of content (12 pages)

PAGE 1
LTC1344A Software-Selectable Cable Terminator U DESCRIPTION FEATURES ■ ■ The LTC ®1344A features six software-selectable multiprotocol cable terminators. Each terminator can be configured as an RS422 (V.11) 100Ω minimum differential load, V.35 T-network load or an open circuit for use with RS232 (V.28) or RS423 (V.10) transceivers that provide their own termination. When combined with the LTC1543 and LTC1544, the LTC1344A forms a complete software-selectable multiprotocol serial port.
PAGE 2
LTC1344A U W U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER I FOR ATIO (Note 1) Positive Supply Voltage (VCC) ................................... 7V Negative Supply Voltage (VEE) ........................... – 13.2V Input Voltage (Logic Inputs) .................... (VEE – 0.3V) to (VCC + 0.3V) Input Voltage (Load Inputs) .................................. ±18V Power Dissipation .............................................. 600mW Operating Temperature Range LTC1344AC ..............................
PAGE 3
LTC1344A U W TYPICAL PERFORMANCE CHARACTERISTICS V.11 or V.35 Differential Mode Impedance vs Supply Voltage (VCC) V.11 or V.35 Differential Mode Impedance vs Common Mode Voltage V.11 or V.35 Differential Mode Impedance vs Temperature 105 VCM = –2V 110 VCM = 0V 105 VCM = 7V 100 –40 –20 0 20 40 60 80 108 106 104 102 100 100 TA = 25°C –6 – 4 –2 0 2 4 6 COMMON MODE VOLTAGE (V) 1344 G01 104 4.6 8 V.35 Common Mode Impedance vs Common Mode Voltage 165 158 TA = 25°C 104 – 5.2 – 5.
PAGE 4
LTC1344A U U U PIN FUNCTIONS M0 (Pin 1): TTL Level Mode Select Input. The data on M0 is latched when LATCH is high. R4B (Pin 15): Load 4 Node B. VEE (Pin 2): Negative Supply Voltage Input. Can connect directly to the LTC1543 VEE pin. Connect a 1µF capacitor to ground. R5B (Pin 17): Load 5 Node B. R1C (Pin 3): Load 1 Center Tap. R6A (Pin 19): Load 6 Node A. R1B (Pin 4): Load 1 Node B. R6B (Pin 20): Load 6 Node B. R1A (Pin 5): Load 1 Node A. LATCH (Pin 21): TTL Level Logic Signal Latch Input.
PAGE 5
LTC1344A W U ODE SELECTIO LTC1344A MODE NAME DCE/DTE M2 M1 M0 R1 R2 R3 R4 R5 R6 V.10/RS423 X 0 0 0 Z Z Z Z Z Z RS530A 0 1 0 0 0 0 1 1 Z Z Z Z Z Z V.11 Z V.11 V.11 V.11 V.11 RS530 0 1 0 0 1 1 0 0 Z Z Z Z Z Z V.11 Z V.11 V.11 V.11 V.11 X.21 0 1 0 0 1 1 1 1 Z Z Z Z Z Z V.11 Z V.11 V.11 V.11 V.11 V.35 0 1 1 1 0 0 0 0 V.35 V.35 V.35 V.35 Z V.35 V.35 Z V.35 V.35 V.35 V.35 RS449/V.36 0 1 1 1 0 0 1 1 Z Z Z Z Z Z V.11 Z V.11 V.11 V.11 V.
PAGE 6
LTC1344A U W U U APPLICATIONS INFORMATION Multiprotocol Cable Termination GENERATOR One of the most difficult problems facing the designer of a multiprotocol serial interface is how to allow the transmitters and receivers for different electrical standards to share connector pins. In some cases the transmitters and receivers for each interface standard can be simply tied together and the appropriate circuitry enabled.
PAGE 7
LTC1344A U U W U APPLICATIONS INFORMATION BALANCED INTERCONNECTING CABLE GENERATOR LOAD GENERATOR BALANCED INTERCONNECTING CABLE CABLE TERMINATION RECEIVER A A' B B' C C' LOAD CABLE TERMINATION RECEIVER 100Ω MIN A A' C C' 1344 F08 1344 F06 Figure 8. Typical V.28 Interface Figure 6. Typical V.11 Interface A A 51.5Ω S1 ON S2 OFF V.11 RECEIVER LTC1344A 51.5Ω S1 OFF Z 124Ω S2 OFF V.28 RECEIVER LTC1344A 124Ω 5k Z 51.5Ω 51.5Ω B B C C IZ 3.25mA –10V 1344 F09 Figure 9. V.
PAGE 8
LTC1344A U U W U APPLICATIONS INFORMATION A BALANCED INTERCONNECTING CABLE GENERATOR LOAD V.35 DRIVER CABLE TERMINATION RECEIVER A' A 50Ω 125Ω 125Ω 50Ω LTC1344A 51.5Ω 124Ω S2 ON S1 ON 51.5Ω B 50Ω B B' C C' 50Ω C1 100pF Figure 12. V.35 Driver Using the LTC1344A Figure 10. Typical V.35 Interface A 51.5Ω S1 ON S2 ON The generator differential impedance must be 50Ω to 150Ω and the impedance between shorted terminals A and B to ground C must be 150Ω ±15Ω.
PAGE 9
LTC1344A U TYPICAL APPLICATIONS N Controller Selectable Multiprotocol DTE/DCE Port with DB-25 Connector C6 C7 C8 100pF 100pF 100pF 3 8 11 12 13 LTC1344A VCC 5V 14 44 C5 1µF 41 LTC1343 D1 6 DTE_TXD/DCE_RXD D2 7 DTE_SCTE/DCE_RXC VEE C12 1µF 8 5 DTE_LL/DCE_TM 2 C4 3.
PAGE 10
LTC1344A U TYPICAL APPLICATIONS N Cable Selectable Multiprotocol DTE/DCE Port with DB-25 Connector C6 C7 C8 100pF 100pF 100pF 3 8 11 12 13 LTC1344A VCC 5V 14 4 D2 7 R1 9 DTE_RXC/DCE_SCTE R2 10 DTE_RXD/DCE_TXD 11 12 NC 13 14 5 4 6 7 9 10 16 15 18 17 19 20 22 23 24 1 VCC 2 23 14 22 24 21 11 DTE DCE TXD A RXD A TXD B RXD B SCTE A RXC A SCTE B RXC B TXC A TXC A TXC B TXC B RXC A SCTE A RXC B SCTE B RXD A TXD A RXD B TXD B D3 8 DTE_TXC/DCE_TXC VEE 24 D1 6
PAGE 11
LTC1344A U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. G Package 24-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 0.318 – 0.328* (8.07 – 8.33) 24 23 22 21 20 19 18 17 16 15 14 13 0.301 – 0.311 (7.65 – 7.90) 1 2 3 4 5 6 7 8 9 10 11 12 0.205 – 0.212** (5.20 – 5.38) 0.068 – 0.078 (1.73 – 1.99) 0° – 8° 0.005 – 0.009 (0.13 – 0.22) 0.022 – 0.037 (0.55 – 0.95) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.
PAGE 12
LTC1344A U TYPICAL APPLICATIO Figure 13 shows a typical application for the LTC1344A using the LTC1543 mixed mode transceiver chip to generate the clock and data signals for a serial interface. The LTC1344A VEE supply is generated from the LTC1543 charge pump and the select lines M0, M1, M2 and DCE/DTE are shared by both chips. Each driver output and receiver input is connected to one of the LTC1344A termination ports. Each electrical protocol can then be chosen using the digital select lines.