LM25066A: LM25066A/about Voltage, current, power monitor

Kevin Leary

Part Number: LM25066A

We are having trouble calculating the amperage passing thru the 2-milli-ohm RSENSE SHUNT resistor using the LM25066A 2016 Datasheet; the CL=GND. what is the proper equation to determine the current ?

thanks,

over 6 years ago

0 Brian Daugherty over 6 years ago

TI__Expert 5940 points

Kevin

Assume you are using PMBus to read. Use the m,b,r coefficients per table 41, pg 39 of the DS with the normal PMBus protocol.

Brian

0 Kevin Leary over 6 years ago in reply to Brian Daugherty

Prodigy 150 points

We are aware of table-41, could you show the 'amperage' calculation using as follows: 2-milli-ohm shunt, CL=GND, measured voltage across shunt 5-milli-volts ?

0 Brian Daugherty over 6 years ago in reply to Kevin Leary

TI__Expert 5940 points

5/2 = 2.5Amps

0 Kevin Leary over 6 years ago in reply to Brian Daugherty

Prodigy 150 points

yes, ohms' law...E/R=I

I am asking for how to calculate the current using the M,B,R equation with the 12-bit READ_IIN number from the LM25066A ?

0 Brian Daugherty over 6 years ago in reply to Kevin Leary

TI__Expert 5940 points

Best for you to pull the PMBus specification (1.2). Data is processed by the host system through PMBus standard protocol. Essentially convert Hex data out to Decimal and using equation 2, page 39 right above table 41 m,b, r coefficients. Equation 2 is a form of an equationof a line. m = slope (hence Rsns impacts), b = y intercept. It is important to have the PMBus standard understood as it applies to all serial telemetry info coming from the LM25066A. You will need to be very good with this to use at the system level.

Brian

0 Kevin Leary over 6 years ago in reply to Brian Daugherty

Prodigy 150 points

Could you send me an example amperage calculation using the M,B,R etc...the issue is the datasheet is not complete.

0 Brian Daugherty over 6 years ago in reply to Kevin Leary

TI__Expert 5940 points

Kevin,

There isn't much I can provide that isn't in the DS or explained here. You need be up on PMBus and serial communication. Do you have a local FAE that can work with you?

Brian

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LM25066A: LM25066A/about Voltage, current, power monitor