Datasheet

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LTC2870/LTC2871

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FuncTion Tables

Table 1. LTC2870 Mode Selection Table

FEN 485/232 RXEN DXEN TE485 H/F LB

DC/DC

CONVERTER MODE AND COMMENTS

0 X 1 0 0 X X OFF Low Power Shutdown: All Main Functions Off

0 0 1 0 X X X OFF Low Power Shutdown: All Main Functions Off

1 X 1 0 0 X X ON Fast-Enable: DC/DC Converter On Only

X 0 X 1 X X 0 ON RS232 Drivers On

X 0 0 X X X 0 ON RS232 Receivers On

X 1 X 1 X X 0 ON RS485 Driver On

X 1 0 X X X 0 ON RS485 Receiver On

X 1 X X 1 X X ON RS485 Driver and Receiver 120Ω Termination Enabled

X 1 X X X 0 0 X RS485 Full-Duplex Mode

X 1 X X X 1 0 X RS485 Half-Duplex Mode

X 1 0 X X X 1 ON RS485 Loopback Mode

X 0 0 X X X 1 ON RS232 Loopback Mode

Table 2. LTC2871 Mode Selection Table (CH2 = 0)

FEN RX232 DX232 RX485 DX485 TE485 H/F LB

DC/DC

CONVERTER MODE AND COMMENTS

0 1 0 1 0 0 X X OFF Low Power Shutdown: All Main Functions Off

1 1 0 1 0 0 X X ON Fast-Enable: DC/DC Converter On Only

X X 1 X X X X 0 ON RS232 Drivers On

X 0 X X X X X 0 ON RS232 Receivers On

X X X X 1 X X 0 ON RS485 Driver On

X X X 0 X X X 0 ON RS485 Receiver On

X X X X X X 0 0 X RS485 Full-Duplex Mode

X X X X X X 1 0 X RS485 Half-Duplex Mode

X X X 0 X X X 1 ON RS485 Loopback Mode

X 0 X X X X X 1 ON RS232 Loopback Mode

Table 3. RS232 Receiver Mode (485/232 = 0 for LTC2870, CH2 = 0 for LTC2871)

RX232 OR RXEN

RECEIVER INPUTS

(A, B, RIN1, RIN2) CONDITIONS

RECEIVER OUTPUTS

(RA, RB, ROUT1, ROUT2)

LTC2870 RECEIVER INPUTS

(A, B)

LTC2871 RECEIVER INPUTS

(RIN1, RIN2)

1 X No Fault Hi-Z 125kΩ Hi-Z

0 0 No Fault 1 5kΩ 5kΩ

0 1 No Fault 0 5kΩ 5kΩ

0 X Thermal Fault Hi-Z 5kΩ 5kΩ

Table 4. RS232 Driver Mode (485/232 = 0 for LTC2870, CH2 = 0 for LTC2871)

DX232 OR DXEN

DRIVER INPUTS

(DY, DZ, DIN1, DIN2) CONDITIONS

LTC2870 DRIVER OUTPUTS

(Y, Z)

LTC2871 DRIVER OUTPUTS

(DOUT1, DOUT2)

0 X No Fault 125kΩ Hi-Z

1 0 No Fault 1 1

1 1 No Fault 0 0

X X Thermal Fault 125kΩ Hi-Z

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