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8.10 ADC Averaging
The ADC12 control provides capability for averaging of ADC results. The averaging module utilizes a
modified moving average (MMA) algorithm, to reduce hardware resources and avoid the need to store up
to 32 ADC samples per result. Averaging is provided on the first 6 result registers (ADC Result Register 0-
5). Averaged ADC results can be read by firmware in the ADC Averaged Result Registers following
completion of an ADC conversion sequence.
Modified Moving Average (MMA) algorithm is a type of IIR filter defined by the following equation:
Y[n] = X[n] / N + Y[n - 1]*(N - 1) / N
where
•
X[n] is the new sample
•
Y[n] is the average value
•
N is the number of averaged samples
Firmware can select from 4 options for ADC averaging (4X, 8X, 16X, 32X):
•
4-sample moving average: 1/4 of current sample and 3/4 of previous average
•
8-sample moving average: 1/8 of current sample and 7/8 of previous average
•
16-sample moving average: 1/16 of current sample and 15/16 of previous average
•
32-sample moving average: 1/32 of current sample and 31/32 of previous average
The averaging result register is stored immediately following the calculation of the moving average. Upon
receipt of the next ADC sample, the ADC sample value and current moving average are used for
calculation of the next moving average. In addition, 5 fractional bits from the moving average calculation
are stored for use in the next moving average calculation. These fractional bits ensure better accuracy of
the moving average over time.
NOTE: No oversampling or decimation is used during the averaging process. The average value is
calculated over several separate consecutive sequences of conversion. Therefore the non
averaged result is always more responsive than the averaged result.
8.11 Temperature Sensor
The ADC-12's channel-14 is internally connected to a temperature sensor. The internal sensor may be
used for purposes like overtemperature protection and/or temperature compensation of control related
parameters like voltage reference or switching frequency. Some applications may require additional
external temperature sensor/s for measurement of switching stage temperature/s and for copper trace
current sensing temperature compensation.
In order to activate the internal temperature sensor the following bit in TEMPSENCTRL register at
Chapter 8
need to be cleared.
MiscAnalogRegs.TEMPSENCTRL.bit.TEMP_SENSE_DIS = 0;
SNIU028A – February 2016 – Revised April 2016
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ADC Averaging
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