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KL03 time to wait after bandgap buffer is enabled

Question asked by Martin Krause on Mar 21, 2016
Latest reply on Mar 21, 2016 by Kerry Zhou

How long do I have to wait after enabling the bandgap buffer on an KL03 MCU before the read ADC value for the bandgap channel is stable? In the datasheet / user manual there is no time specified.

I'm asking, because when I do not wait any time, and just enable the bandgap buffer and then immediately afterwards do an ADC measurement of the bandgap, the ADC value "jumps" at higher MCU temeratures (> 50°C). If I add an delay of about 2 us, between enabling the bandgap buffer and measuring the internal bandgap voltage, the ADC value for the bandgap stops jumping, even at higher MCU temeratures (>80°C). My MCU runs at the 8 MHz internal clock, when I do this measurements, the ADC-Clock runs on ADC asynchronous clock source with ADLPC = 0 and ADHSC = 1.

 

So I assume, there is a waiting time after enabling the bandgap buffer, before I should do measue the ADC bandgap channel to get stable values. The question is how long should I wait to get stable values over the whole MCU temperature range?

 

Best Regards,
Martin

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