ACPL-782T-500E 查看數據表（PDF） - Avago Technologies
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ACPL-782T-500E Datasheet PDF : 18 Pages
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Application Information
Power Supplies and Bypassing
The recommended supply connections are shown in
Figure 17. 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 ACPL-782T
through an RC anti-aliasing filter (R2 and C2). Although the
application circuit is relatively simple, a few recommenda-
tions should be followed to ensure optimal performance.
The power supply for the ACPL -782T is most often obtained
from the same supply used to power the power transis-
tor 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 trans-
former 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.
As shown in Figure 18, 0.1 PF bypass capacitors (C1, C2)
should be located as close as possible to the pins of the
ACPL-782T. The bypass capacitors are required because
of the high-speed digital nature of the signals inside the
ACPL-782T. A 0.01μF bypass capacitor (C2) is also rec-
ommended at the input due to the switched-capacitor
nature of the input circuit. The input bypass capacitor
also forms part of the anti-aliasing filter, which is recom-
mended to prevent high-frequency noise from aliasing
down to lower frequencies and interfering with the
input signal. The input filter also performs an important
reliability function—it reduces transient spikes from ESD
events flowing through the current sensing resistor.
HV+
+
GATE DRIVE
CIRCUIT
***
FLOATING
POWER
SUPPLY
-
MOTOR
***
+ R1 -
RSENSE
D1
5.1 V
R2
39 :
C1
0.1 μF
C2
0.01 μF
***
HV-
Figure 17. Recommended Supply and Sense Resistor Connections.
ACPL-782T
13
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