INA138 Output Voltage Error

Jared Becker

Genius 11945 points

Other Parts Discussed in Thread: INA138

Hi Team,

I am using the INA138 with the following setup:

Rs = 0.4 Ohm

RL = 265k Ohm

V+ and Vin+ are tied together at 6V

Load current = 250mA

I calculate that I should get an output voltage = 0.25 * 0.4 * 265000 / 5000 = 5.3V

However, I am only getting an output voltage = 1.53V

I tested this on two board.

Can you please help me understand why this is happening?

Thank you,

Jared

over 9 years ago

0 Mayrim Verdejo over 9 years ago

TI__Genius 15770 points

Hi Jared,

You should be getting 5.3V in the output. What are you using to test this? Is this a pcb board or just bread board (prototyping) setup? If it is a PCB can you send us the schematic and pcb layout?

Regards,

0 Jared Becker over 9 years ago in reply to Mayrim Verdejo

TI__Genius 11945 points

Hi Mayrim,

Thank you for your excellent support! As it turns out, the shunt value I had on my board was incorrect. It was actually a 0.10 Ohm resistor instead of a 0.40 Ohm resistor.

What kept throwing me off was that my multimeter kept indicating that the resistor value was 0.40. It must not be able to go as low as 0.10.

I switch to a 0.50 Ohm shunt and now I am seeing 5.3V on the output, which is what I expect.

Thank you for your help!

Best regards,
Jared

0 Mayrim Verdejo over 9 years ago in reply to Jared Becker

TI__Genius 15770 points

Hi Jared,

Great news! It was great working with you over the phone for troubleshooting.

Regards

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INA138 Output Voltage Error