Is Vbus input always connected to the rail being measured? Also, what is impedance range for Vbus input?

N Maris

Part Number: INA226

Hi I cannot determine from the datasheet if the INA226 Vbus pin is always loading the rail being measured at the pin, irregardless of whether or not it is measuring Vbus, or is it switched in or out depending upon whether or not the device is measuring Vbus voltage or shunt voltage? It seems to imply that the amplifier is always connected and that the ADC is switched to the Vbus amplifier as required, but wanted to verify that this is the case.

Also the datasheet specs a typical value for the Vbus impedance of 830 kohm, but no min/max values are supplied. What is the range of impedance values?

Thanks.

over 5 years ago

0 N Maris over 5 years ago

Prodigy 210 points

FYI I searched the forum posts and I found that the impedance range variation spec in another post, +/- 15% tolerance with 25 ppm tempco, however still cannot find anything indicating that Vbus is disconnected from the rail when not measuring Vbus.

0 Peter Iliya over 5 years ago in reply to N Maris

TI__Mastermind 32395 points

Hello N Maris,

Thank you for posting your question. The VBUS pin will always possess an 830 kΩ common-mode input resistance, thus it will always act as a resistive load to the bus rail it is sensing/connected to. This is true even if the iNA226 is programmed to only sense the shunt voltage.

Also the ±15% tolerance and 25ppm is appropriate for VBUS impedance.

Please come back with any other questions you may have.

Best,

Peter

0 N Maris over 5 years ago in reply to Peter Iliya

Prodigy 210 points

Thanks Peter!

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Is Vbus input always connected to the rail being measured? Also, what is impedance range for Vbus input?