HCNR201-300E Avago Technologies US Inc., HCNR201-300E Datasheet - Page 18

• Manufacturer Part Number: HCNR201-300E
• Description: OPTOCOUPLER ANLG DC-1MHZ GW 8SMD
• Manufacturer: Avago Technologies US Inc.

Specifications of HCNR201-300E

• Output Type: Linear Photovoltaic
• Input Type: DC
• Package / Case: 8-SMD Gull Wing
• Number Of Channels: 1
• Voltage - Isolation: 5000Vrms
• Current Transfer Ratio (min): 0.36% @ 10mA
• Current Transfer Ratio (max): 0.72% @ 10mA
• Current - Dc Forward (if): 25mA
• Mounting Type: Surface Mount, Gull Wing
• Current Transfer Ratio: 0.36 % to 0.72 %
• Forward Current: 1 mA to 20 mA
• Isolation Voltage: 5000 Vrms
• Minimum Forward Diode Voltage: 1.2 V
• Output Device: Photodiode
• Configuration: 1 Channel
• Maximum Forward Diode Voltage: 1.95 V
• Maximum Reverse Diode Voltage: 2.5 V
• Maximum Input Diode Current: 25 mA
• Maximum Power Dissipation: 60 mW
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: - 55 C
• No. Of Channels: 1
• Optocoupler Output Type: Photodiode
• Input Current: 20mA
• Output Voltage: 15V
• Opto Case Style: SMD
• No. Of Pins: 8
• Forward Voltage: 1.6V
• Rohs Compliant: Yes
• Forward Current If: 25mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Current - Output / Channel: -
• Vce Saturation (max): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 516-1609-5

The preceding circuits were pre sented to illustrate the
fl exibility in designing analog isolation circuits using the
HCNR200/201. The next section presents several com-
plete schematics to illustrate practical applications of the
HCNR200/201.
Example Application Circuits
The circuit shown in Figure 16 is a high-speed low-cost
circuit designed for use in the feedback path of switch-
mode power supplies. This application requires good
bandwidth, low cost and stable gain, but does not re-
quire very high accuracy. This circuit is a good example
of how a designer can trade off accuracy to achieve
improve ments in bandwidth and cost. The circuit has a
bandwidth of about 1.5 MHz with stable gain character-
istics and requires few external components.
Although it may not appear so at fi rst glance, the circuit
in Figure 16 is essentially the same as the circuit in Fig-
ure 12a. Amplifi er A1 is comprised of Q1, Q2, R3 and R4,
while amplifi er A2 is comprised of Q3, Q4, R5, R6 and R7.
The circuit operates in the same manner as well; the only
diff erence is the performance of amplifi ers A1 and A2.
The lower gains, higher input currents and higher off set
voltages aff ect the accuracy of the circuit, but not the
way it operates. Because the basic circuit operation has
not changed, the circuit still has good gain stability. The
use of discrete transistors instead of op-amps allowed
the design to trade off accuracy to achieve good band-
width and gain stability at low cost.
To get into a little more detail about the circuit, R1 is se-
lected to achieve an LED current of about 7-10 mA at the
nominal input operating voltage according to the fol-
lowing equation:
where K
0.5%. R2 is then selected to achieve the desired output
volt age according to the equation,
The purpose of R4 and R6 is to improve the dynamic re-
sponse (i.e., stability) of the input and output circuits by
lowering the local loop gains. R3 and R5 are selected to
provide enough current to drive the bases of Q2 and Q4.
And R7 is selected so that Q4 operates at about the same
collector current as Q2.
The next circuit, shown in Figure 17, is designed to achieve
the highest possible accuracy at a reasonable cost. The
high accuracy and wide dynamic range of the circuit is
achieved by using low-cost precision op-amps with very
low input bias currents and off set voltages and is limited
by the performance of the opto coupler. The circuit is de-
signed to operate with input and output voltages from
1 mV to 10 V.
18
1
I
V
F
(i.e., I
OUT
= (V
/V
IN
PD1
IN
/R1)/K1,
= R2/R1.
/I
F
) of the optocoupler is typically about
The circuit operates in the same way as the others. The
only major diff erences are the two compensa tion capaci-
tors and additional LED drive circuitry. In the high-speed
circuit discussed above, the input and output circuits are
stabilized by reducing the local loop gains of the input
and output circuits. Because reducing the loop gains
would decrease the accuracy of the circuit, two compen-
sation capacitors, C1 and C2, are instead used to improve
circuit stability. These capacitors also limit the bandwidth
of the circuit to about 10 kHz and can be used to reduce
the output noise of the circuit by reducing its bandwidth
even further.
The additional LED drive circuitry (Q1 and R3 through
R6) helps to maintain the accuracy and band width of the
circuit over the entire range of input voltages. Without
these components, the transcon duc t ance of the LED
driver would decrease at low input voltages and LED
currents. This would reduce the loop gain of the input
circuit, reducing circuit accuracy and bandwidth. D1 pre-
vents excessive reverse voltage from being applied to
the LED when the LED turns off completely.
No off set adjustment of the circuit is necessary; the gain
can be adjusted to unity by simply adjusting the 50 kohm
poten tiometer that is part of R2. Any OP-97 type of op-
amp can be used in the circuit, such as the LT1097 from
Linear Technology or the AD705 from Analog Devices,
both of which off er pA bias currents, μV off set voltages
and are low cost. The input terminals of the op-amps and
the photodiodes are connected in the circuit using Kelvin
connections to help ensure the accuracy of the circuit.
The next two circuits illustrate how the HCNR200/201 can
be used with bipolar input signals. The isolation amplifi er
in Figure 18 is a practical implemen tation of the circuit
shown in Figure 14b. It uses two opto couplers, OC1 and
OC2; OC1 handles the positive portions of the input sig-
nal and OC2 handles the negative portions.
Diodes D1 and D2 help reduce crossover distortion by
keeping both amplifi ers active during both positive and
negative portions of the input signal. For example, when
the input signal positive, optocoupler OC1 is active while
OC2 is turned off . However, the amplifi er control ling OC2
is kept active by D2, allowing it to turn on OC2 more rap-
idly when the input signal goes negative, thereby reduc-
ing crossover distortion.
Balance control R1 adjusts the relative gain for the posi-
tive and negative portions of the input signal, gain con-
trol R7 adjusts the overall gain of the isolation amplifi er,
and capac i tors C1-C3 provide compensa tion to stabilize
the amplifi ers.