SBAS978A June 2019 – May 2020 ADS7028
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
In the ADS7028, any one analog input channel can be selected for computing the RMS result. The RMS result is computed over a block of samples from the selected channel and result can be read from the RMS_RESULT_LSB and RMS_RESULT_MSB registers. As shown in Equation 4, compute the RMS result with the 16-bit square root mean of the accumulated result of the squares of the ADC conversion data.
In Equation 4, D is the data corresponding to the analog input channel selected for RMS measurement and N is the number of samples over which RMS is computed. The DC offset must be subtracted from the AC component because the analog input signal to the ADC is unipolar. DC subtraction can be enabled or disabled, given by b in Equation 4, by configuring the DC_SUB field. When DC subtraction is enabled, the DC input voltage must be within ±5% tolerance of the mid-scale voltage, for example (0.5 × AVDD) ±5%.
The size of a 1-LSB RMS result is given in Equation 5 and the RMS result is 16 bits long.
The procedure for using the RMS module is outlined in the steps below: