The A/D input impedance is so high that accurate A/D conversion cannot be performed. What should I do to solve this problem?|FAQ|ROHM Semiconductor

FAQ's

The A/D input impedance is so high that accurate A/D conversion cannot be performed. What should I do to solve this problem?
- When the A/D input impedance is high, charging to the internal capacitor of the A/D converter circuit may not be completed within the A/D conversion time, thus possibly resulting in worsened conversion accuracy. The following shows three measures against this problem.
  - Add an external large capacitor, such as 0.2 uF or 0.47 uF, to the A/D input pin.
  - Set the SACK bit of SA-AD control register 0 to "1" and select the longer conversion time (approximately 41.26 us).
  - Repeatedly convert the same A/D input pin to increase the time to charge the internal capacitor. (This is because a residual charge, which was A/D converted last time, is left in the internal capacitor at the next conversion.)
  Fig. 1
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