9.2.1.2.12.1.1 Gain Error Correction

Gain Error Correction: For a 5V cell voltage, -19.4 mV to 19.4 mV in 255 steps (8 bits) in the CELL*_GAIN registers (one per channel) Procedure:

1. Set the CELL ADC to 1MHz frequency, 256 Decimation Ration, Corner freqeuncy to 1.2 Hz for best results.
2. Apply voltage VIN1, read back from ADC VOUT1 in the VCELL*_LF, VCELL*_HF registers, and record both.
3. Apply voltage VIN2, read back from ADC VOUT2 in the VCELL*_LF, VCELL*_HF registers, and record both.
4. Find the gain error correction (GEC) at 5 V (5V is used regardless of VINx value) and write the 8-bit value to the CELL*_GAIN register.
   1. Calculate slope m = (VOUT2–VOUT1) / (VIN2–VIN1)
   2. The gain error is calculated at 5V. Thus Gain Error=[(5V*m)-5V]
   3. The Gain Shift value is 19.4mV*2/255=0.15mV
   4. Then take the negative of the gain and divide it by the gain shift to find bit shift required Bit Shift=(-Gain Error)/(Gain Shift)
   5. Then convert bit shift to a two’s complement hex value
   6. Make sure that if the bit shift is greater than “127”, the hex value will be “7F”
   7. Make sure that if the bit shift is less than “-128”, the hex value will be “80”
   8. Finally enter the calculated Hex value to CELL*_Gain
5. Repeat steps 1-3 on each cell voltage
6. Perform the steps in Offset Error Correction.