AD5940 LPDAC Calibration & Excitation Signal

Hi,

I have a few questions regarding the AD5940.


1) LPDAC calibration: Can you give me more information how the calculations of the parameters (bC2V_DACXB, kC2V_DACxB) are done in the function "AD5940_LPDACCal"? For example, it is unclear to me where the factor 1e3f/32768*1.835f/1.82f comes from.

2) LPDAC calibration: I have a deviation from the expected output for both the 6 and 12 bit output of the LPDAC. For example, with a register value (Vzero0/6bit output) of 0x00, I expect a voltage of 200mV according to the datasheet, but I only measure 190mV. I was hoping that the LPDAC calibration would minimize the deviation. Is there a configuration or setup to minimize these deviations/tolerances?

3) LPDAC calibration: I used the formula from the example code (ad5940.h) (Code(LSB) = kV2C_DACxB * Voltage(mV) + bV2C_DACxB) to calculate the register value for a given voltage. Again, I was able to find a discrepancy. For example, if I want to achieve a voltage of 800mV, I get a calculated register value of 0x11. However, the measured voltage at the LPDAC output is only 730mV. Probably this is related to the calculated factors from the function "AD5940_LPDACCal". Am I missing something or why do I still have deviations even after calibration?

4) Excitation signal: Is it possible to set a negative voltage between the excitation signal and the voltage at the Vzero0 pin (voltage at SE0)?

thanks in advance