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Hi ,
what is the calibration value for the following configuration
R shunt = 0.001 ohm
Max_Expected_I = 3A
I calculated the result according to datasheet as bellow
Cal = trunc [ 0.04096 / (0.0001*0.001) ] = 409600 (DEC) = 110 0100 0000 0000 0000 (BIN)
But calibration register only consists of 2 bytes
how can I enter calibration register ?
Hello Austin,
Thank you for using the TI forum. Although you did the calculation correctly, The reason you got a Cal value out of the register size range is because the chosen shunt resistor is not a good size for this application. Using the the error analysis tool on the product page and using the A version with some assumed values in the calculator with a 2mΩ shunt, we get:
From this tool, you can see that the error is very high. If you change the shunt to 10mΩ, then you error improves quite a bit:
This brings your Cal value to 40960, which will fit in the register.
I recommend looking at our "Getting Started with Digital Power Monitors" app note found here: https://www.ti.com/lit/pdf/sboa511. This document also has a link to a calculator tool to help pick the shunt resistor.
Regards,
Mitch
Hi Mitch,
is there a default setting for the calibration register? Do I need to program calibration register before reading power from it?
Thanks,
Tony
Hey Tony,
The default value for the calibration register is 0, and the calibration register does need to be programmed before the registers will update, per the datasheet:
Regards,
Mitch