SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
Zero offset error is defined as the difference between the voltage at midcode (2048) and 0.9V (for 1.8V reference voltage). DAC offset error is calibrated using an external 1.8V reference voltage and loaded into the DAC offset trim register by default. If the DAC is used at any reference voltage other than 1.8V, the offset trim must be adjusted to ensure that offset error performance stays within the device-specific data manual limits. The default DAC trim can be overridden from the EFUSE_OVERRIDE_DAC_TRIM register of TOP_CTRL.DAC0_TRIM register.
Follow the equations below to determine the custom trim value (reference voltage other than 1.8V) to be added to [7:0] bits of DACTRIM register.
Trim value of 0 to 127 corresponds to a negative value. So the effective formula for DACOUT becomes :
DACOUT = ((DACVALA-OFFSET_TRIM)/4096) * DACVREF * (33/18)
Trim value of 128 to 255 corresponds to a positive value. So the effective formula for DACOUT becomes
DACOUT = ((DACVALA-OFFSET_TRIM+256)/4096) * DACVREF * (33/18)
The DAC register space (CONTROLSS_DAC) is not used for any DAC trim function. Changing the default DAC offset trim using EFUSE_OVERRIDE_DAC_TRIM register is not recommended and only meant for debug or diagnostic purpose.