Datasheet

10
t
p
– ENABLE PROPAGATION DELAY – ns
-60 100
200
0
T
A
– TEMPERATURE –°C
-40 0 20 60 80
HCPL-4200 fig 14
40-20
150
100
50
V
CC
C
L
= 15 pF
t
PHZ
t
PZH
20 V
4.5 V
4.5 V
20 V
t
p
– ENABLE PROPAGATION DELAY – ns
-60 100
100
0
T
A
– TEMPERATURE –°C
-40 0 20 60 80
HCPL-4200 fig 15
40-20
80
60
20
V
CC
C
L
= 15 pF
t
PLZ
t
PZL
20 V
4.5 V
4.5 V
20 V
40
Figure 14. Typical Logic High Enable Propagation Delay vs. Temperature.
Figure 15. Typical Logic Low Enable Propagation Delay vs. Temperature.
Figure 16. Test Circuit for Common Mode Transient Immunity.
Applications
Data transfer between equipment which employs current
loop circuits can be accomplished via one of three congu-
rations: simplex, half duplex or full duplex communication.
With these congurations, point-to-point and multidrop
arrangements are possible. The appropriate conguration
to use depends upon data rate, number of stations, num-
ber and length of lines, direction of data ow, protocol,
current source location and voltage compliance value, etc.
Simplex
The simplex conguration, whether point to point or
multidrop, gives unidirectional data ow from transmit-
ter to receiver(s). This is the simplest conguration for
use in long line length (two wire), for high data rate,
and low current source compliance level applications.
Block diagrams of simplex point-to-point and multi-
drop arrangements are given in Figures 17a and 17b
respectively for the HCPL-4200 receiver optocoupler.
For the highest data rate performance in a current loop,
the conguration of a non-isolated active transmitter
(containing current source) transmitting data to a re-
mote isolated receiver(s) should be used. When the cur-
rent source is located at the transmitter end, the loop is
charged approximately to V
MI
(2.5 V). Alternatively, when
the current source is located at the receiver end, the loop
is charged to the full compliance voltage level. The lower
the charged voltage level the faster the data rate will be.
In the congurations of Figures 17a and 17b, data rate is
independent of the current source voltage compliance
level. An adequate compliance level of current source
must be available for voltage drops across station(s)
during the MARK state in multidrop applications or for
long line length. The maximum compliance level is de-
termined by the transmitter breakdown characteristic.
A recommended non-isolated active transmitter
circuit which can be used with the HCPL-4200 in
point-to-point or in multidrop 20 mA current loop ap-
plications is given in Figure 18. The current source is
controlled via a standard TTL 7407 buer to provide
high output impedance of current source in both the ON