Application Information
Power Supplies and Bypassing
The recommended supply
connections are shown in
Figure 16. 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-7510
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-7510 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 transformer.
Otherwise, some sort of simple
isolated supply can be used,
such as a line powered
transformer or a high-
frequency DC-DC converter.
An inexpensive 78L05 three-
terminal regulator can also be
used to reduce the floating
supply voltage to 5 V. To help
attenuate high- frequency
power supply noise or ripple,
a resistor or inductor can be
used in series with the input
of the regulator to form a
low-pass filter with the
regulator’s input bypass
capacitor.
HV+
GATE DRIVE
CIRCUIT
+
FLOATING
POSITIVE
SUPPLY
-
R4
R2
MOTOR
39
Ω
+ R1 -
R
SENSE
D1
5.1 V
C1
0.1 µF
1 V
DD1
2 V
IN+
C2
0.01 µF
3 V
IN-
4 GND1
HCPL-7510
HV-
Figure 16. Recommended supply and sense resistor connections.
11
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