The ADC sampling based on a 3.6 V reference voltage, the chip inside with built-in 300 k ohm resistance?Can you remove?

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The 2020-05-26 04:01 Tue
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MintCandy5
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The ADC sampling based on a 3.6 V reference voltage, the chip inside with built-in 300 k ohm resistance?Can you remove?

We adopt the ADC sampling a precision resistor voltage, based on a 3.6 V reference voltage, set the GP_ADC_ATTN3X.But measured voltage value, and we have a larger theoretical value difference.We check manual found Figure 55, chip inside are two built-in parallel resistor, added up to 300 k ohms.Our understanding is correct, please?In addition, the two resistance can cancel?

Keywords:
The ADC built-in parallel resistance
Device:
DA14580
The 2020-06-02 09:27 Tue
CYibin
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Joined:The 2017-12-14 02:48
hello

hello

The internal resistance can't remove.

Precision can be improved through the following points.

0. Prefer using VBAT test for the channel

1. Do not use the internal voltage divider (disable GP_ADC_ATTN3X)

2. Using precise resistance as 1:3 external voltage divider, total resistance is less than 1 k.

3. Software, after each sampling, delay us again to read value is 1.