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PSoC™ 6

GuNo_288966
Contributor

Hi, I have a custom board with CYBLE-416045-02. It is powered by a powerbank.

The power supply of the CYBLE can be interrupted by a MOSFET switch. If interrupted, the powerbank goes to sleep after a few seconds, the output voltage drops to 2,3V. This is ok and works as intended.

The problem is that I have an analog input pin for voltage measurement. There is a voltage divider of 27kOhm to the plus input and 10kOhm to ground. Even if the powerbank sleeps, there are still 0,62V present at the analog input pin. As a result, VDD goes to 0,33V, and some other I/O pins also stay at 0,33V. The PSoC6 is not running but also not completely off. I need the output pins to be at 0V when the PSoC6 is not powered.

When the 27kOhm resistor is removed, VDD and the other pins all go to GND level as intended.

I understand that this is a kind of back powering issue. I had a similar issue with UART and a PSoC4 that could be solved by adding a 10kOhm resistor in the RX line.

Here I have a 27kOhm resistor between the voltage source and the input pin, the voltage is lower, and still face issues.

I also understand that a pin with hot swap ability should be used, but there are no such pins on the CYBLE-416045-02.

What can I do to solve this problem?

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1 Solution
Vasanth
Moderator
Moderator

Hi,

The module does not have pins which has hot swap capability. One solution to solve this back powering is to add another mosfet on top of the 27K, which can be turned on from a pin in PSoC. One additional pin should be used for this. The mosfet will be tuned off when PSoC is OFF and will not back-power the pin. You may take a slight hit on the accuracy of ADC results.

Best Regards,
Vasanth

View solution in original post

1 Reply
Vasanth
Moderator
Moderator

Hi,

The module does not have pins which has hot swap capability. One solution to solve this back powering is to add another mosfet on top of the 27K, which can be turned on from a pin in PSoC. One additional pin should be used for this. The mosfet will be tuned off when PSoC is OFF and will not back-power the pin. You may take a slight hit on the accuracy of ADC results.

Best Regards,
Vasanth

View solution in original post

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