Electrical Considerations
The HCPL-5760, HCPL-5761,
HCPL-576K or 5962-89477
optocoupler has internal
temperature compensated,
predictable voltage and current
threshold points which allow
selection of an external resistor,
Rx, to determine larger external
threshold voltage levels. For a
desired external threshold voltage,
V±, a corresponding typical value
of Rx can be obtained from Figure
10. Specific calculation of Rx can
be obtained from Equation (1) of
Figure 11. Specification of both V+
and V- voltage threshold levels
simultaneously can be obtained by
the use of Rx and Rp as shown in
Figure 11 and determined by
Equations (2) and (3).
Figure 9. Operating circuit for burn-in and steady state life tests.
Rx can provide over-current
transient protection by limiting
input current during a transient
condition. For monitoring contacts
with a relay or switch, the HCPL-
5760/1/K, or 5962-89477 combin-
Figure 10. Typical external threshold characteristic, V vs. Rx.
±
ation with Rx and Rp can be used to For interfacing ac signals to TTL
allow a specific current to be con-
ducted through the contacts for
cleaning purposes (wetting current).
systems, output low pass filtering
can be performed with a pullup
resistor of 1.5 kΩ and 20 µF
capacitor. This application
requires a Schmitt trigger gate to
avoid slow rise time chatter
For two specifically selected
external threshold voltage levels,
V+ and V-, the use of Rx and Rp will
permit this selection via
The choice of which input voltage
clamp level to choose depends
equations (2), (3) provided the
following conditions are met:
upon the application of this device problems. For ac input applica-
(see Figure 3). It is recommended
that the low clamp condition be
used when possible to lower the
input power dissipation as well as
the LED current, which minimizes
LED degradation over time.
tions, a filter capacitor can be
placed across the dc input
terminals for either signal or
transient filtering.
V+ VTH+
––– ≥ ––– and ––+–––––– < ––––
VTH- V - VTH- ITH-
V - VTH+
ITH+
V
-
-
Either ac (Pins 1, 4) or dc (Pins 2,
3) input can be used to determine
external threshold levels.
VTH- (V+ ) - VTH+ (V )
In applications where dVCM/dt may
be extremely large (such as static
discharge), a series resistor, RCC,
-
Rx = –––––––––––––––––––– (2)
ITH+ (VTH-) - ITH- (VTH+
)
For one specifically selected
should be connected in series with external threshold voltage level V+
VCC and Pin 8 to protect the or V-, Rx can be determined
RP =
detector IC from destructively high without use of Rp via
surge currents. See note 14 for
VTH- (V ) - VTH+ (V )
+
-
–––––––––––––––––––––––––––(3)
ITH+ (V - VTH-) + ITH- (VTH+ - V )
determination of RCC. In addition,
it is recommended that a ceramic
disc bypass capacitor of 0.01 µF to
0.1 µF be placed between Pins 8
and 5 to reduce the effect of power
supply noise.
V+ - VTH+
-
+
(-)
(-)
Rx = –––––––––
ITH+
(1)
See Application Note 1004 for
more information.
(-)
9
AVAGO [ AVAGO TECHNOLOGIES LIMITED ]
