HCPL-4100 Datasheet, PDF (10/12 Pages) Agilent(Hewlett-Packard) – Optically Coupled 20 mA Optically Coupled 20 mA

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 differentV values. 25% distor-
CC
tion data rate is defined 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 supply levels, as illustrated in Figure 15. In addition,
CC
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%.
The cable used contained five 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.
40
36
V _CC = 0.00212 —mV (L) + 5.7 V
32 _{R CABLE = 0.05296 Ω/m}
28 ^{ILOOP = 20 mA}
V _MARK = 2.7 Vdc (HCPL-4100)
24 V _SAT = 1.5 Vdc (CURRENT SOURCE)
20
T _A = 25 °C
16
12
8
4
0
0
100
1000
10000
L – LOOP LENGTH (ONE DIRECTION) METERS
Figure 14. Minimum Required Supply Voltage, V , vs.
CC
Loop Length for Current Loop Circuit of Figure 13.
Figure 15. Typical Data Rate vs. Distance and
Supply Voltage.
10