INA209: Calculating measurement error

Gerry Hawkins

Part Number: INA209
Other Parts Discussed in Thread: INA226, INA231, INA300

Hello,

This part measures shunt voltage to infer current and bus voltage. I am attempting to evaluate the measurement error across the input and voltage current range of my application and would like some clarification as to the meaning of the figures stated in the datasheet.

My application has an 11-13V bus voltage input range, Vsense from 0-38mV, across a temperature range of 0 to 85 degrees celcius.

Typically I would sum the offset voltage error, gain error, and quantisation error to calculate the overall error on a given measurement.

In this instance that is not possible as the bus voltage offset and gain error is not specified (although graphs of typical performance are given, I need to know the maximum values of these parameters).

So my questions are:

1) What do the "current measurement error" and "bus voltage measurement error" specifications given in the "DC ACCURACY" section of the datasheet correspond to?

2) In order to calculate the overall measurement error across the range of operating conditions in my application, should I simply assume 1% worst case current measurement error for both current and voltage and manually add the quantisation errors to these measurements?

3) Are you able to supply the maximum bus voltage offset and bus gain error specifications for this part?

Thanks in advance,

Gerry

over 4 years ago

0 Patrick Simmons over 4 years ago

TI__Mastermind 21730 points

Hello Gerry,

Thanks for considering to use Texas Instruments. I am looking into your inquiry. As this part was released in 2007 and some of the engineers responsible for the part are no longer at TI, it will take some time to find.

0 Gerry Hawkins over 4 years ago in reply to Patrick Simmons

Prodigy 40 points

Thank you, Patrick.

Meanwhile, is there an equivalent but newer part I should consider? Bandwidth and accuracy are the key parameters in my application.

Kind regards,

Gerry

0 Patrick Simmons over 4 years ago in reply to Gerry Hawkins

TI__Mastermind 21730 points

Hello Gerry,

Im still looking into your original question. However, if you are looking for a digital part with similar bandwidth, I would recommend the INA226 and INA231. These parts have more of their error specs better defined.

0 Gerry Hawkins over 4 years ago in reply to Patrick Simmons

Prodigy 40 points

Hello Patrick,
Having reviewed these parts, unfortunately they aren't suitable for us due to the lack of integrated fast comparator. The 5us overcurrent warning of the IN209 is required by our application.
Kind regards,
Gerry

0 Patrick Simmons over 4 years ago in reply to Gerry Hawkins

TI__Mastermind 21730 points

Hello Gerry,

So for your original questions, here is what I can say.

1) Current measurement error and bus voltage measurement correspond to the total of all errors combined for the current and bus measurements.

2) For worst case you can assume 1% worst case for both current and bus measurement error and that includes quantisation.

3) I will not be able to supply you with the max bus voltage offset and gain error specifications for this part.

0 Patrick Simmons over 4 years ago in reply to Patrick Simmons

TI__Mastermind 21730 points

Hello Gerry,

I looked through our portfolio and we do not have another power monitor with an integrated comparator for over current warnings. The next best option I could provide you would be adding an external comparator like our INA300 with whichever power monitor you feel best satisfies your accuracy requirement. However, the best typical alert propagation delay of our INA300 is 10us.

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INA209: Calculating measurement error