Low side bidirectional current sensing

Michael Lawton

Prodigy 50 points

Is the common mode range of a current sense amplifier relative to the chips ground?
The voltage across a 100mV shunt in a bidirectional application will be -100mV to +100mV
In a low side application one side of the shunt will be connected to ground so the shunt voltage will be ±100mV relative to ground
The common mode range of many of your current sense amplifiers which say they are low side and bidirectional capable only extends to 0V
Therefore using the shunt as described above would cause the amplifier inputs to go outside the specified common mode range

What am I missing?

over 9 years ago

0 Mayrim Verdejo over 9 years ago

TI__Genius 15760 points

HI Michael,

In low side applications Vcm ~ 0V. Please refer to training video series Section 2& 3 for more detailed explanation.

e2e.ti.com/.../467332

0 Michael Lawton over 9 years ago in reply to Mayrim Verdejo

Prodigy 50 points

Hi Mayrim

Thanks for your reply. I actually found the answer just after submitting this question - I should have been looking at the datasheet not the parametrics.

Although the parts say a common mode range down to 0V on the description page (e.g. www.ti.com/.../INA226) that is the common mode bus voltage range. The actual full common mode range in the datasheet shows that the input can go below 0V.

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Low side bidirectional current sensing