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PSOC™4 HV PA: ADC resolution range of voltage/temperature and current - KBA237883

PSOC™4 HV PA: ADC resolution range of voltage/temperature and current - KBA237883

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Version: *A

Question:
Why is there a variation in the PSoC™ 4 HVPA voltage/temperature resolution, which is 16-bit*1, and   the current resolution, which is 23-bit*2?

Answer:

  • The basic resolution of the ADC is 16 bits (the delta-sigma modulator in the PACSS is 16-bit).
    For example, the configuration of voltage/temperature channels are as follows:
  • gain = 1
  • moving average = 1
  • SHIFTL = 0
  • DEC_SHIFTR = 0,

So, it gets the native 16-bit resolution.

  • The current channel has an additional automatic gain control (AGC).
    At that setting, the configurations are as follows:
  • moving average = 4 (2-bit shift left)
  • SHIFTL = 8
  • DEC_SHIFTR=3

So, it gets an effective shift left*3 of seven bits (i.e., the native 16-bit is now 23-bit).

*1: See SID100, SID131 in the PSoC™ 4 HVPA DS
*2: See SID117 in the PSoC™ 4 HVPA DS
*3: The effective shift left value is a combination of the following:

  • SHIFTL
  • Moving average
  • DEC_SHIFTR

The equation for the effective shift left is as follows:

SHIFTL + log2(Moving Average) - DEC_SHIFTR

Effective left shift = 8 + log2(4) - 3

 = 8 + 2 - 3

 = 7

The other settings increase the analog gain and reduce the shift left, resulting in the same overall current resolution.

For more details on AGC, see section 1.8.5 of the PSoC™ 4 HVPA DS or section 21.2.4 of PSoC™ 4 HVPA Architecture TRM. Contact your local Infineon sales representative for access to these documents.

Note: This KBA applies to the following series of PSoC™ 4 HV family MCUs:

  • PSoC™ 4 HVPA series
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