2
Quick Start Procedure
The HCPL-4562/HCNW4562 Evaluation Kit is fully assem-
bled and tested. Following procedures guide you to oper-
ate this board.
This kit is recommended for optocoupler evaluation and
application reference only, Avago Technologies cannot
assume responsibility for use of any circuitry other than
circuitry entirely embodied in this board. No circuit patent
licenses are implied.
1. Verify there should not be any interconnection
between input and output side circuits.
2. Verify both 5 VDC and 9 VDC power supply are set
right voltage output, do not turn on any power supply
before all are connected. The Evaluation Kit both
power supplies are recommended within maximum
15 VDC.
3. Connect 5 VDC power supply to input side J1, and 9
VDC power supply to output side J2.
4. Connect input signal from signal generator to B1, and
measurement equipment oscilloscope to B2. Don’t
turn on output of signal generator.
5. Turn on 5 VDC power supply.
6. Measure voltage at point VB and VE, VB is around 1.15
V and VE around 0.5 V.
7. Turn on 9 VDC power supply.
8. Turn on signal generator output, adjust oscilloscope
setting to measure output waveform. This circuit is
designed for a typical 1 Vp-p input signal.
9. Adjust resistor R4 get desired gain G
V
.
10. The Kit is designed AC output signal with C2= 2.2
µF capacitor coupling, when JU1 is shorted with a
shunt, the output signal is DC coupled. DC coupling is
recommended if it is acceptable in design system. Or
user can apply AC coupling via other capacitor with
JU1 shorted.
Detailed Description
Figure 1 shows a schematic circuit for wide-bandwidth
analog/video application and an amplifier design. This is
an ac input coupled and ac output coupled circuit. The
LED input current IF is set at a recommended 6 mA for the
HCPL-4562 or 10 mA for the HCNW4562 by selecting an
appropriate value for the R4. If the VCC1 on the input side
is 5 V the voltage VB established by the resistor divider R1
and R2 at the base of Q1 (neglecting base current drop
across R3) is approx. 1.15 V. This establishes the voltage
VE at the emitter of Q1 around 0.5 V. Adjust R4 to set the
recommended LED current at 6 mA. With 0.5 V at VE the
resistor R4 is selected to be approx. 70 Ω for 6 mA of IF.
For isolating a composite video signal, VCC1 is recom-
mended increasing to 9V so that transistor Q1 has higher
bias voltage VB, and R4 can have more space to be ad-
justed.
With a VCC2 supply between 9 to 12 V, the value of R11
is selected to keep the output voltage at midpoint of the
supply at approx. 4.25 V with the collector current ICQ4 of
Q4 at approx. 9 mA.
ICQ4
≈
Vo/R11
≤
4.25V/470 Ω
≤
9 mA
The small signal model of the bipolar transistors can de-
termine the overall voltage gain of the circuit and gain
stages involved and is found to be
G
V
≈
V
OUT
/ V
IN
≈
∂
I
PB
/
∂
I
F
[R
7
R
9
/(R
4
R
10
)]
Where
∂
I
PB
/
∂
I
F
is the base photo current gain (photo di-
ode current gain) and is indicated as a typical of 0.0032 in
the data sheet.
Adjust resistor R
4
to achieve the desired voltage gain.
The voltage gain of the second stage (Q3) is approximate-
ly equal to
R
9
/ R
10
• / [1 + sR
9
(C
CQ3
+1/(2
p
R
11'
f
T4
) )]
Where R
11'
is the parallel combination of R
11
and load
impedance and f
T4
is the unity gain frequency Q
4
. From
this equation one can observe that to maximize the band-
width one would want to increase the value of R
11'
or re-
duce the value of R
9
at a constant ratio of R
9
/R
10
.
