Datasheet

10
Figure 13. Recommended Non-Isolated Active Receiver with HCPL-4100 Isolated Transmitter for Simplex Point to Point 20 mA Current Loop.
25% distortion data rate at dierent V
CC
values. 25% distor-
tion data rate is dened as that rate at which 25% distortion
occurs to output bit interval with respect to the input bit
interval. Maximum data rate (dotted line) is restricted by
device characteristics. An input Non-Return-to-Zero (NRZ)
test waveform of 16 bits (0000001011111101) was used
for data rate distortion measurements. Enhanced speed
performance of the loop system can be obtained with lower
V
CC
supply levels, as illustrated in Figure 15. In addition,
when loop current is supplied through a resistor instead
of by a current source, an additional series termination
resistance equal to the characteristic line impedance can
be used at the HCPL-4100 transmitter end to enhance
speed of response by approximately 20%.
Figure 14. Minimum Required Supply Voltage, V
CC
, vs.
Loop Length for Current Loop Circuit of Figure 13.
Figure 15. Typical Data Rate vs. Distance and Supply
Voltage.
V
CC
– VOLTS
0
12
0
L – LOOP LENGTH (ONE DIRECTION) METERS
100 1000
16
4
28
32
36
40
10000
m
V
CC
= 0.00212 — (L) + 5.7 V
R
CABLE
= 0.05296 Ω /m
I
LOOP
= 20 mA
V
MARK
= 2.7 Vdc (HCPL-4100)
V
SAT
= 1.5 Vdc (CURRENT SOURCE)
T
A
= 25 °C
V
24
20
8
The cable used contained ve pairs of unshielded, twisted,
22 AWG wire (Dearborn #862205). Loop current is 20 mA
nominal. Input and output logic supply voltages are 5 V
dc.
Full Duplex
The full duplex point-to-point communication of Fig-
ure 16 uses a four wire system to provide simultane-
ous, bidirectional data communication between local
and remote equipment. The basic application uses
two simplex point-to-point loops which have two
separate, active, non-isolated units at one common
end of the loops. The other end of each loop is isolated.