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Problem with bandgap V conversion

Question asked by sys@allmatic.com on Oct 28, 2014
Latest reply on Oct 29, 2014 by David Sherman

Hello,

 

I'm having troubles with the conversion in subject: I'm using Kinetis MKE02Z32VLH4 (2N22J), mounted on our custom board.

We are supplying VDDA/VREFH and VDD pins with 5V.

The ADC module is set to 12-Bit conversion, with these settings:

- Input clock select: Bus clock/2

- Prescaler: 8 (è frequency ~1048 kHz)

- Long sample time: Enabled

- Low power mode: Disabled

 

Reading Channel No 23 (bandgap), we read a value of 1442 on 4096 (12Bit). Considering that, from datasheet, the bandagap voltage should be about 1.16V, we obtain a Vdd voltage of 3.3V.

 

But we are supplying with 5V... Am I mistaking something? I would expect a value about of 950 corresponding to 1.16V with Vdd = 5V

 

Thanks in advance to all!

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