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Original question:

PGA305: How to write EEPROM Data + CRC Check

PGA305: How to Calculate PGain and POffset

Heiko Muench
Prodigy 80 points
Part Number: PGA305

Hello,

at no point in the data sheet is it documented how the Pgain or POffset factors are composed.
At Default this is:

0x40000044 = 1 //PGain
0x40000045 = 0
0x40000046 = 0
0x40000047 = 0 //POffset
0x40000048 = 0
0x40000049 = 0

At Page42 there is mentioned that P = PGAIN × P ADC + POFFSET

But how are they really calculated? the compensation constants in the registers are 2^22 times of the actual factors, does it mean the constants can be -1 to 1?
what is with Pgain, is there a factor also?

  • 0
    TI__Guru**** 181021 points

    Hello Poster!

    Our support staff is taking time with their families for the Independence Day holiday here in the US.  It may be July 8th before we can get back to you with help on your query.  We apologize in advance for the delay and will get back to you as soon as possible.

  • 0 in reply to Tom Hendrick
    TI__Mastermind 31655 points

    Hi Heiko,

    The PGAIN and POFFSET are actually just as described with no additional scaling factor for either of those values. The decimal value of the PGAIN is what is multiplied by the PADC values. This of course is very limiting since only having integer gains does not allow for very much fine tuning of the gain, but that is simply how it was designed.

    Regards,