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HCNR200 NEED HELP ! [SOLVED]

v1.5

Member
Hi
I designed a circuit containing an hcnr200 analog isolator. I designed this circuit completely according to datasheets. Today, my circuit came from jlcpcb. I started soldering in the evening. First I soldered the part where the hcnr200 is located. it didn't work and I don't know what the problem is. I directly share the diagram of the circuit board I sent to jlcpcb. In the diagram, VCC1 and GND1 are the voltage in the isolated part. This voltage is 12 V. Likewise I used VCC and GND from another source 12v. While the input voltage was 0-10v, I lowered it at 0-3.3v for the convenience of me in the forward steps. I did this with RN1 603x4 10k 1% resistors. I aimed to isolate this with an analog isolator, but regardless of the input voltage of the isolator, I see a constant 300mV voltage from the voltage follower at the output. I changed the output resistors to 10k, 100k or even 10MEG, but nothing changed. All of these resistors are 1% sensitive.
I quoted the circuit diagram from the datasheets in figure 12.b. I had not tried hcnr200 before that. I am using it for the first time and I am still having problems at the first stage of the pcb. I did not solder the next parts of the pcb. I'm testing it cleanly and away from conductors. Having problems at the first stage made me very sad. please help me.
 

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ronsimpson

Well-Known Member
Most Helpful Member
Start at the beginning. Is the output of the first op-amp what you think it should be?
 

v1.5

Member
thanks
The + input of IC2A, the first opamp, is 1/3 of the input voltage as I explained above. Since the first opamp is a voltage follewer, its output has the same voltage. When I test the circuit from the TP7 point, I see 2V at the TP7 test point while the input is 6v. so the first stage is working right.
IC2B, on the other hand, is an opamp required for HCNR200 and I don't know how to test this opamp. because this opamp is responsible for generating constant current.
help please
 

v1.5

Member
I just noticed something new. Up to 358mV the circuit works as it should. but then it does not respond to the increase in input voltage and the output remains at a constant 358mV.
For example: When there is 135mV input voltage in TP7, about 140mV voltage is generated from pin 7 of IC4B. what would be the reason ?
 

v1.5

Member
Hi
I managed to get the circuit to work. After thoroughly reviewing and reviewing the datasheet, I realized that Ipd1 current was too much. then i replaced the R1 and R3 resistors with 100k and it worked. Currently there is only 70mV difference between input and output, which is not a problem for my circuit.
 

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