Connect Tech DFlex-4/104 - page 78

4-28 Chapter 4: Appendix H - 20mA Current Loop
DFlex-4/104 User’s Manual, ver. 0.04
20mA Current Loop SLIM
The 20mA current loop module provides optically isolated 20mA
active or passive current loop interfaces for two ports. For each
port there is an isolated receiver, an optically isolated transmitter
and two 20mA current sources. See Figure 20 for the schematic
of the 20mA current loop module.
Note:. The current source uses a compliance voltage of 24 volts,
and the transmitter will withstand a 27 volt drop. Please refer to
the Hewlett Packard Optoelectronics Manual/Catalogue for a
complete description of HPCL 4100 and HPCL 4200
specifications.
Figure 20: 20mA Current Loop SLIM schematic
33 Ohm
51 Ohm
VF = 1.5V
-12V
RxD SRC
+12V
RxD RET
2N2907A
22K
+5V
+5V +5V
3 TxD +
TxD 6
4 TxD -
HCPL
4100
5
8
HCPL
4200
8
56
RxD 7
1 RxD +
2 RxD -
CTS
DCD
33 Ohm
51 Ohm
VF = 1.5V
-12V
RxD SRC
+12V
RxD RET
2N2907A
22K
20mA Current Loop SLIM
Partial Schematic
Where:
SLIM
Pin No.
Current Loop
Signal
SLIM
Pin No.
Current Loop
Signal
2
TxD(
-
)1
14
RxDReturn 2
3 TxD Source 1 15 TxD Return 2
4 RxD(+) 1 16 RxD Source 2
5 TxD(+) 1 17 RxD(-) 2
6 RxD Return 1 18 Gnd
7 TxD Return 1 19 +12 V
8 RxD Source 1 20 -12 V
9 RxD(-) 1 21 +5 V
10 TxD(-) 2 22 DCD 2 (+5 V)
11 TxD Source 2 23 CTS 2 (+5 V)
12 RxD(+) 2 32 CTS 1 (+5 V)
13 TxD(+) 2 33 DCD 1 (+5 V)