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Voltage divider before ADC MKL17Z256

Question asked by Samuel Conti on Jun 23, 2016
Latest reply on Jun 26, 2016 by Samuel Conti

Hello,

 

In a design with a MKL17Z256 ( Vcc = 2V8), I use the ADC16 to read the voltage of a battery -3V3 to 4V2). So I must to place a voltage divider before the ADC to reduce the voltage. At this moment I use a 27K/47K but thses resistors are so big and I have a voltage drop in my ADC result (and the datasheet p32 says that a little resistance source is needed to drive the ADC). For example, instead of 4V15, I read 4V07. It's a bit much....So I will decrease these resistors values.

 

My question is : must the 2 resistors be low ? or just one of the two ? (which one ?)

 

In fact I would like to use the more bigger resistors possible to avoid current consumption through this voltage divider, it's battery powered design. Si if I can use a big resistor on 2 it will be good.

 

Thank you,

 

Sam,

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