Datasheet

LTC2870/LTC2871
17
28701f
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 120 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 125k Hi-Z
0 0 No Fault 1 5k 5k
0 1 No Fault 0 5k 5k
0 X Thermal Fault Hi-Z 5k 5k
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 125k Hi-Z
1 0 No Fault 1 1
1 1 No Fault 0 0
X X Thermal Fault 125k Hi-Z