TPS53667: Read value of 8Ch

Hi Yuto,

The first thing I would check on your design is the IMON resistor value. Does the populated resistor match the calculated value? Is the calculated resistor value correct (i.e. double check your math)?

I suggest this because assuming the correct value was placed on the PCB, VIMAX (0.85V) would correspond to a current of 377A. That's pushing past the capabilities of a six phase design and seems unlikely. 

After checking this resistors I would then double check the initial IMAX settings. If you're using the pin-strapping options make sure the correct resistors are populated on the F-IMAX pin. For NVM settings, make sure the pre-programmed IMAX value is correct. The wrong IMAX value will affect the scaling seen on IMON and could affect your results.

Once those options get straightened out, you can also use the IOUT_CAL_OFFSET register to further improve your current sense accuracy. Simply apply a known load current. Read the READ_IOUT register and subtract the register value from the applied current to get your offset error. Then write the correct offset value into the register.

Example: 50A load is applied, 49A is read. 49A - 50A = -1A = offset error. Since the error is -1A an offset of +1A should be written to IOUT_CAL_OFFSET to cancel our the error.

Let me know if you have any questions.

Cheers,

Carmen

Hi Yuto,

A 1kΩ difference wouldn't cause all the issues you're seeing. Have you checked the F-IMAX divider to make sure it's setting the correct IMAX value? Is the IMAX register reading correct? I'd also check the OFFSET register too just to make sure it's initially 0 like it's supposed to be.

As for CSP pins they should sit at 1.7V DC so that's expected. The value of those pins will change at 5mV/A, ±2.5%. Typically to see those small changes the scope would need to be AC coupled.

Cheers,

Carmen