13
For two specifically selected
external threshold voltage levels,
V+ and V , the use of RX and RP
-
will permit this selection via
equations (2), (3) provided the
following conditions are met. If
the denominator of equation (2)
is positive, then
Figure 13. External Threshold Voltage Level Selection.
Electrical Considerations
V+
VTH+
VTH-
V+ - VTH+ ITH+
The HCPL-0370/3700/3760
optocouplers have 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
In applications where dVCM/dt
≥
and
<
may be extremely large (such as
static discharge), a series resistor,
RCC, should be connected in
series with VCC and Pin 8 to pro-
tect the detector IC from destruc-
tively high surge currents. See
Note 13 for determination of RCC
In addition, it is recommended
that a ceramic disc bypass
V
-
V - VTH-
-
ITH-
Conversely, if the denominator of
equation (2) is negative, then
V+
VTH+
VTH-
V+ - VTH+ ITH+
.
≤
and
>
V
-
V - VTH-
-
ITH-
voltage, V , a corresponding
±
typical value of RX can be ob-
tained from Figure 12. Specific
calculation of RX can be obtained
from Equation (1). Specification
of both V and V voltage
threshold levels simultaneously
can be obtained by the use of RX
and RP as shown in Figure 13 and
determined by Equations (2) and
(3).
capacitor of 0.01 µF be placed
between Pins 8 and 5 to reduce
the effect of power supply noise.
VTH- (V+ ) - VTH+ (V )
-
RX =
RP =
(2)
ITH+ (VTH-) - ITH- (VTH+
)
For interfacing ac signals to TTL
+
-
VTH- (V+ ) - VTH+ (V )
-
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
problems. For ac input applica-
tions, a filter capacitor can be
placed across the dc input
terminals for either signal or
transient filtering.
(3)
ITH+ (V -VTH-)+ ITH-(VTH+ -V+ )
-
RX can provide over-current
transient protection by limiting
input current during a transient
condition. For monitoring con-
tacts of a relay or switch, the
HCPL-0370/3700/3760 in
www.agilent.com/ semiconductors
For product information and a complete list of
distributors, please go to our web site.
Either ac (Pins 1, 4) or dc
(Pins 2, 3) input can be used to
determine external threshold
levels.
For technical assistance call:
combination with RX and RP can
be used to allow a specific current
to be conducted through the
contacts for cleaning purposes
(wetting current).
Americas/ Canada: +1 (800) 235-0312 or
(916) 788-6763
Europe: +49 (0) 6441 92460
China: 10800 650 0017
Hong Kong: (+65) 6756 2394
For one specifically selected
external threshold voltage level
India, Australia, New Zealand: (+65) 6755 1939
The choice of which input voltage
clamp level to choose depends
upon the application of this
device (see Figure 1). It is recom-
mended that the low clamp
Japan: (+81 3) 3335-8152 (Domestic/ Interna-
tional), or 0120-61-1280 (Domestic Only)
V or V, RX can be determined
+
-
without use of RP via
Korea: (+65) 6755 1989
V - V
+
(-) TH+ (-)
Singapore, Malaysia, Vietnam, Thailand,
Philippines, Indonesia: (+65) 6755 2044
RX =
(1)
condition be used when possible.
Taiwan: (+65) 6755 1843
ITH+
(-)
Data subject to change.
Copyright © 2004 Agilent Technologies, Inc.
Obsoletes 5989-0785EN
December 20, 2004
The low clamp condition in
conjunction with the low input
current feature will ensure
extremely low input power
dissipation.
5989-2101EN
HP [ HEWLETT-PACKARD ]
