SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
The internal EADC output is a 6 bit two’s complement number. Depending on AFE gain, the least significant EADC bit can have a value of 1 to 8 mV. To simplify automatic AFE gain changes, this EADC output is shifted depending on the AFE gain, giving a 9 bit output to the filter.
This way, regardless of the AFE gain, the least significant bit will always have a resolution of 1mV. Depending on AFE gain, the bits and range of the output actually used will change:
Analog Gain | AFE_GAIN Bits | Input Range (mV) | Bits Used | Left Shift | Measurement Resolution (mV) |
---|---|---|---|---|---|
1 | 0 | +248 to -256 | 3 - 8 | 3 | 8 |
2 | 1 | +124 to -128 | 2 - 7 | 2 | 4 |
4 | 2 | +62 to -64 | 1 - 6 | 1 | 2 |
8 | 3 | +31 to -32 | 0 - 5 | 0 | 1 |
Here is a graphical representation of the EADC output:
The EADC error output as described above can be read from the EADC raw value register:
eadc_error = FeCtrl0Regs.EADCRAWVALUE.bit.RAW_ERROR_VALUE;
It is also sent to the Filter, and is one of the values which can be used by the digital comparators controlled by the Fault Mux.