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PSoC 5, 3 & 1 MCU

Anonymous
Not applicable

Hello, I'm trying to use an external reference voltage (1.25V) in my design. The problem is that I've got a ripple (+-50mV) which depends on the conversion rate / ADC-clock. I've selectet 'Externel Vref on P0[3]', do I have to do more? It seems that this GPIO is not very high impedance or so..? If I switch the reference to internal, my external reference looks nice, so I excluded problems with my external design.

   

Had anyone ever a similar problem?

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3 Replies
HeLi_263931
Honored Contributor II

Didi you add a decoupling cap on P0[3]? This is recommended for the reference voltage.

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Anonymous
Not applicable

If I do so, the ripple increases. In other designs I used the 'internal bypassed' mode with external decoupling C and never had problems..

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HeLi_263931
Honored Contributor II

Sounds as if you get oscillations on your reference voltage. How is it generated, maybe it cannot cope with an external capacitance?

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