MC33772B Gain compensation issue

[marco_hsu]

During the current acquisition function test of MC33772B, we found that there will be current jump at specific temperature points (around -24℃, 1℃, 24℃, 45 ℃ and 110 ℃). Is this phenomenon related to the IC gain and offset compensation mechanism? How to disable gain and offset compensation mechanism?

[JozefKozon · Accepted solution]

Dear Marco,

the temperature gain compensation cannot be turned off. You can only load your own calibration values from your own EEPROM through the I2C interface. This is however not recommended by NXP. NXP provides parts with optimal calibration values already loaded in the chip. For the gain compensation description, please refer to the MC33772B datasheet from the page 56.

With Best Regards,

Jozef

[marco_hsu]

Hi JozefKozon,

thanks for your reply.

Because of the procute design, there is no external EEPROM in our board.

Is it possible to overwrite the deafult compensated date via other way?

[JozefKozon]

Hi Marco,

I apologize I made a mistake here. You can change the default data in the Mirror memory registers once they are loaded from the Fuses Cell Array (the internal memory), but you would need to change the date in the Mirror Memory registers after each MC33772B power up or reset. After each power up or reset are the Mirror Memory registers loaded again with the Fuses Cell Array data or from external EEPROM is used. 

For the Mirror Memory Access procedure, please refer to the section 9.23 in the MC33772B datasheet.

With Best Regards,

Jozef

[marco_hsu]

Hi Jozef,

Our product is compensated temperature effect in our factory, we compensates -30~105 degree C. So we don't need the calibration mechanism.

Is there other method to avoid the gain calibration mechanism? The standard calibration value will affect out compensation result.

Thanks

[JozefKozon]

Hi Marco,

unfortunately no. The gain compensation cannot be turned off and if no external EEPROM is used, the calibration values from gain compensation are loaded from internal memory, which is read only. Please see below a question from another customer regarding the internal memory.

1. As I understand, Fuse Memory is read only and there is no way to erase or corrupt it, correct?

[Answer]: Yes, you're correct, no way to erase it nor to corrupt it, unless a multiple fault occurs.

With Best Regards,

Jozef

[marco_hsu]

Hi Jozef,

I already accept that the compensate value can't be erased and the mechanism can't be disabled.

Is it possible to read out the Fuses Cell Array value and we do the inverse-calibration back?

Thanks