HCPL7850300 Avago Technologies US Inc., HCPL7850300 Datasheet - Page 13

• Manufacturer Part Number: HCPL7850300
• Manufacturer: Avago Technologies US Inc.

Specifications of HCPL7850300

• Operating Supply Voltage (typ): 5V
• Lead Free Status / RoHS Status: Not Compliant

Applications Information
Functional Description
Figure 23 shows the primary functional blocks of the HCPL-
7850. In operation, the sigma-delta modulator converts
the analog input signal into a high-speed serial bit stream.
The time average of this bit stream is directly proportional
to the input signal. This stream of digital data is encoded
and optically transmitted to the detector circuit. The
detected signal is decoded and converted back into an
analog signal, which is filtered to obtain the final output
signal.
Application Circuit
The recommended application circuit is shown in Figure
24. 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
three-terminal voltage regulator (U1). The voltage from
CONDITIONS: I
Figure 28. Operating Circuit for Burn-In and Steady State Life Tests.
13
Figure 25. Single-Supply Post-Amplifier Circuit.
1
3
2
4
27
HCPL-7850
1 k
1 k
U2
GND
V
V
V
T
IN+
IN–
DD
CC
A
=+125˚C
=17.5mA
1
2
3
4
8
7
6
5
+
–
+5 V
C4
0.1 µF
150 pF
+
–
10.0 K
10.0 K
R1
R2
C6
20.0 K
R4A
8
7
5
6
+5 V
V
V
V
GND
DD
OUT+
OUT–
R4B
20.0 K
27
1 k
1 k
–
+
+5 V
U3
150 pF
10.0 K
MC34071
C5
R3
0.1 µF
C8
0.1 µF
the current sensing resistor, or shunt (Rsense), is applied
to the input of the HCPL-7850 through an RC anti-aliasing
filter (R5, C3). And finally, the differential output of the
isolation amplifier is converted to a ground-referenced
single-ended output voltage with a simple differential
amplifier circuit (U3 and associated components).
Although the application circuit is relatively simple, a few
recommendations should be followed to ensure optimal
performance.
Supplies and Bypassing
As mentioned above, an inexpensive three-terminal
regulator can be used to reduce the gate-drive power
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.
V
OUT
(+)
(–)
5.5 V
V
DD
DC
Figure 26. Top Layer of Printed Circuit
Board Layout.
Figure 27. Bottom Layer of a Printed
Circuit Board Layout.
TO R
TO R
SENSE+
SENSE–
TO V
DD1
R5
C3
C2
C4
TO V
V
V
OUT+
OUT–
DD2