S32k14x datasheet ADC needs RS<5K, and no RF and RL values

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S32k14x datasheet ADC needs RS<5K, and no RF and RL values

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jacky_Tan
NXP Employee
NXP Employee

Foryou used R235 (560k)+ R213(56k) resistors to detect input Battery voltage by ADC, because their infotainment produces need total current <100uA in low power mode as OEM required , the battery voltage normal range is 9-16V. this battery detected circuit can pass their low and high temperature test. but S32k14x datasheet needs RS<5K, and no RF and RL values. Foryou needs to know if this circuit has risk , and need to check if it will impact ADC convert accuracy and range.

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lukaszadrapa
NXP TechSupport
NXP TechSupport

Hi Jacky,

there's an old app note talking about this:

https://www.nxp.com/docs/en/application-note/AN2438.pdf 

See section "Input Leakage Offset Error".

It's always a compromise between accuracy and current consumption.

If output impedance of measured signal is too high (and it is very high in this case) then you won't achieve accuracy specified in the datasheet.

Regards,

Lukas

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