PSOC 4200 GPIO pin high should be high impedance?

[DaHu_285096]

I am detecting a voltage (present or not) from 5V USB connector. The measured voltage with plug connected is 5V in to a resistive divider.

The series resistor is 1k and 10k to ground with 1 100n cap across the 10k and also a 3V zener.

In creator I have set the pin to High Impedance. The voltage of the divider should be around 3V (4.5V is output but it should be clamped by the Zener to around 3V).

However, when I measure the voltage I only see 2.6V?

The pin being used is P4.0 and I have it creating an interrupt on change (high or low).

[Vasanth]

Hello David,

The voltage is 2.6V only when you are shorting the divider output to the pin 4[0]? Is it 3V when you are not shorting the output point to the GPIO? One more question, did you select "High impedance analog" in the drive mode option ?

Best Regards,
VSRS

[DaHu_285096]

What do you mean by "shorting the divider output"? I have a resistive divider with Zener across output to prevent input voltage rising above the 3V supply. VDetect Pin is set up as high impedance, the 5V input is the measured USB power voltage and the 2.6V is what I get at input of the GPIO pin.

[Anonymous · Accepted solution]

David,

Few things to check-

1. What is the minimum zener current that needs to be satisfied for regulation?

2. Is there anything else on Pin P3.1 on the board which can load the circuit?

3. What is the device VDD? Device can get back powered via IO if lower by 0.5V compared to pin voltage.

-Rajiv