DRV8305-Q1: Calculation of output of current shunt amplifier

Chase Jeong

Mastermind 8545 points

Part Number: DRV8305-Q1

Tool/software:

Dear TI experts,

My customer wants to calculate the output of current shunt amplifier based on the equation in the datasheet. (page 25)

My customer set the variants as below ;

V_vref = 5V (same as VREF)

K = 2 (offset)

G = 10 (gain setting)

SNx-SPx = 1mV (actually measured value)

And by the equation, Vo = (5/2)-(10*(0.001)) = 2.49V.

But by actual measurement, they measured 3.7V.

Are there anything which I missed for exact calculation? Please let me know.

Best regards,

Chase

over 1 year ago

0 Akshay Rajeev Menon over 1 year ago

TI__Mastermind 25971 points

Hey Chase,

Thank you for the question. I will aim to provide feedback before the end of the week.

Best,
Akshay

0 Chase Jeong over 1 year ago in reply to Akshay Rajeev Menon

Mastermind 8545 points

Dear Akshay,

Please let me know if there are any updates about the issue above. Thanks.

Best regards,

Chase

0 Anthony Lodi over 1 year ago in reply to Chase Jeong

TI__Mastermind 29676 points

Hi Chase,

Akshay is out of office till Thursday, I appreciate your patience on this.

Regards,

Anthony Lodi

0 Akshay Rajeev Menon over 1 year ago in reply to Chase Jeong

TI__Mastermind 25971 points

Hey Chase,

Your calculation looks correct.
Can the customer measure the output voltage when the SP=SN shorted = 0v?

Also how were the measurements taken?

Also is the customer using calibration bit to calibrate the amplifier? - • "Minimize DC offset and drift through temperature with DC calibrating through SPI register. When DC calibration is enabled, device will short input of current shunt amplifier and disconnect the load. DC calibrating can be done at anytime, even when the MOSFET is switching because the load is disconnected. For best result, perform the DC calibrating during switching off period when no load is present to reduce the potential noise impact to the amplifier."

Best,

Akshay

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DRV8305-Q1: Calculation of output of current shunt amplifier