Datasheet

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LTC1344

Software-Selectable

Cable Terminator

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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

1344 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

LTC1343, the LTC1344 forms a complete software-select-

able multiprotocol serial port. A data bus latch feature

allows sharing of the select lines between multiple inter-

face ports.

The LTC1344 is available in a 24-lead SSOP.

Daisy-Chained Control Outputs

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Data Networking

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CSU and DSU

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Data Routers

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

LTC1343

RTSDTRDSR DCDCTS RL

D3D4

LTC1343

TXDSCTETXCRXCRXDTM

LL A (141)

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

TM A (142)

SGND (102)

SHIELD (101)

21424111512179314192023622 810513 21 7 1625

1344 TA01

DB-25 CONNECTOR

LTC1344

D3D4

TXC A (114)

TXC B

RL A (140)

DCD A (109)

DCD B

DSR A (107)

DSR B

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATION

Summary of content (12 pages)

PAGE 1
LTC1344 Software-Selectable Cable Terminator U FEATURES ■ ■ DESCRIPTIO The LTC ® 1344 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 LTC1343, the LTC1344 forms a complete software-selectable multiprotocol serial port.
PAGE 2
LTC1344 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 Operating Temperature Range LTC1344C ............................................... 0°C to 70°C LTC1344I ...........................................
PAGE 3
LTC1344 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.
PAGE 4
LTC1344 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 LTC1343 VEE pin. R5B (Pin 17): Load 5 Node B. R1C (Pin 3): Load 1 Center Tap. R4A (Pin 16): Load 4 Node A. R5A (Pin 18): Load 5 Node A. 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.
PAGE 5
LTC1344 W U ODE SELECTIO LTC1344 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 Reserved 0 1 0 0 1 1 0 0 Z V.11 Z V.11 Z V.11 V.11 Z V.11 Z V.11 Z 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 RS530/RS449/V.36 0 1 1 1 0 0 1 1 Z Z Z Z Z Z V.11 Z V.11 V.
PAGE 6
LTC1344 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
LTC1344 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 LTC1344 51.5Ω S1 OFF Z 124Ω S2 OFF V.28 RECEIVER LTC1344 124Ω 5k Z 51.5Ω 51.5Ω B B C C IZ 3.25mA –10V 1344 F09 Figure 9. V.
PAGE 8
LTC1344 U U W U APPLICATIONS INFORMATION A BALANCED INTERCONNECTING CABLE GENERATOR LOAD V.35 DRIVER CABLE TERMINATION RECEIVER 50Ω 124Ω A' A 125Ω 125Ω 50Ω B B' C C' 50Ω S2 ON S2 ON S1 ON B 50Ω C1 100pF 1344 F10 C 1344 F12 Figure 12. V.35 Driver Using the LTC1344 A S1 ON 51.5Ω 51.5Ω Figure 10. Typical V.35 Interface 51.5Ω LTC1344 Z and B to ground C must be 150Ω ±15Ω.
PAGE 9
LTC1344 U TYPICAL APPLICATIONS N Figure 13 shows a typical application for the LTC1344 using the LTC1343 mixed mode transceiver chip to generate the clock and data signals for a serial interface. The LTC1344 VEE supply is generated from the LTC1343 charge pump and the select lines M0, M1, M2, DCE and LATCH are shared by both chips. Each driver output and receiver input is connected to one of the LTC1344 termination ports. Each electrical protocol can then be chosen using the digital select lines.
PAGE 10
LTC1344 U TYPICAL APPLICATIONS N Controller Selectable Multiprotocol DTE Port with DB-25 Connector C6 100pF C7 100pF 3 C8 100pF 8 11 12 13 LTC1344 VCC 5V 14 1 2 4 3 C5 1µF 41 8 D2 7 DTE_SCT/DEC_RXC D3 9 D4 10 12 13 DTE_TXC/DCE_TXC R1 14 DTE_RXC/DCE_SCTE R2 15 DTE_RXD/DCE_TXD DTE_TM/DCE_LL R1 100k 3 VCC C12 1µF 6 DTE_RTS/DCE_CTS 7 DTE_DTR/DCE_DSR 9 10 12 13 DTE_DCD/DCE_DCD 38 37 36 D2 D3 35 34 33 D4 R2 R3 28 27 R4 20 CTRL 22 LATCH 11 INVERT 25 423 SET 21 DCE 19 M2 18
PAGE 11
LTC1344 U TYPICAL APPLICATIONS N Cable Selectable Multiprotocol DTE Port with DB-25 Connector C6 100pF C7 100pF 3 C8 100pF 8 12 13 11 LTC1344 VCC 5V 14 1 2 4 3 C5 1µF 41 8 D4 10 12 13 DTE_TXC/DCE_TXC R3 32 31 30 29 28 27 16 R4 20 CTRL 22 LATCH 11 INVERT 25 423 SET 26 21 DCE 19 M2 18 M1 17 M0 R1 14 DTE_RXC/DCE_SCTE R2 15 DTE_RXD/DCE_TXD R1 100k 40 GND 23 LB C11 1µF C9 1µF C12 1µF 44 43 42 CHARGE PUMP 41 8 6 7 DTE_DTR/DCE_DSR 9 10 12 13 DTE_DCD/DCE_DCD R2 100k LB D3 10
PAGE 12
LTC1344 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. G Package 24-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 8.07 – 8.33* (0.318 – 0.328) 24 23 22 21 20 19 18 17 16 15 14 13 7.65 – 7.90 (0.301 – 0.311) 1 2 3 4 5 6 7 8 9 10 11 12 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) 0.55 – 0.95 (0.022 – 0.037) NOTE: DIMENSIONS ARE IN MILLIMETERS *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.