HCPL788J Datasheet, PDF (13/20 Pages) Agilent(Hewlett-Packard) – Isolation Amplifier with Short Circuit and Overload Detection

13
R2
39 Ω
INPUT
+
CURRENT _RSHUNT
0.02 Ω
R1
.01 µF
C3
0.1 µF
ISOLATED +5 V
C1
0.1 µF
1
C2
2
V_IN+
V_IN-
HCPL-788J
GND₂ 16
V_DD2 15
3 C_H
FAULT 14
4 C_L
ABSVAL 13
5 V_DD1
V_OUT 12
6 V_LED1+
V_REF 11
7 V_DD1
V_DD2 10
8 GND₁
GND₂ 9
C6
0.1 µF
R3 4.7 kΩ
µC
TO OTHER
PHASE OUTPUTS
C8 C4 C7 C5
A/D
V_REF
GND
Figure 25. Recommended Applications Circuit.
+5 V
C5 = C7 = C8 = 470 pF
C4 = 0.1 µF
HV+
GATE DRIVE
CIRCUIT
R4
+
FLOATING
POWER
SUPPLY
–
MOTOR
+ ^R1 +
R_SENSE
R2
39 Ω
D1
5.1 V
HV-
C1
0.1 µF
C2
0.01 µF
5 V_DD1
HCPL-788J
GND₂ 16
1 V_IN+
V_DD2 15
2 V_IN-
FAULT 14
8 GND₁
ABSVAL 13
7 V_DD1
V_OUT 12
3 C_H
V_REF 11
4 C_L
V_DD2 10
6 V_LED+
GND₂ 9
Figure 26. Recommended Supply and Sense Resistor Connections.
Analog Interfacing
Power Supplies and Bypassing
The recommended supply con-
nections are shown in Figure 26.
A floating power supply (which in
many applications could be the
same supply that is used to drive
the high-side power transistor) is
regulated to 5 V using a simple
zener diode (D1); the value of
resistor R4 should be chosen to
supply sufficient current from
the existing floating supply. The
voltage from the current sensing
resistor (Rsense) is applied to the
input of the HCPL-788J through
an RC anti-aliasing filter (R2 and
C2). Although the application
circuit is relatively simple, a
few recommendations should
be followed to ensure optimal
performance.
The power supply for the
HCPL-788J is most often obtained
from the same supply used to
power the power transistor gate
drive circuit. If a dedicated
supply is required, in many cases
it is possible to add an additional
winding on an existing trans-
former. Otherwise, some sort of
simple isolated supply can be
used, such as a line powered