INA220: About INA220 shunt voltage detection

Hello Vera,

My team and I will look into this and get you support soon. In the meantime, could you please provide schematic information such as the measured current, shunt resistor, and ADC conversion time?

Also, what temperature is making the device output stable? And what is the expected output?

Sincerely,
Peter Iliya
Current Sense Applications

hi Peter,
thank you for the reply!
sorry that I haven't gotten the sch from customer yet.
as for the shunt voltage measured is 6mV~30mV, and shunt resistor is several mOhm, ADC conversion time is 68ms. and using +/-80mV measuring range.
we did not measure the brd temp yet, but the whole brd is still in room temp, just be heat up for a while it could cause it stable.
for the expected output, for an example, for the 154W power, stable output will be 171~172 W, while when the issue happens, the output will drift from 160+~190+W.

Hello Vera,

The device readings should not be drifting this much.

1. What is the Vbus voltage?
2. Is the shunt current being measured a PWM signal or is it DC?
3. Is there an input filter being used?
4. Is this a high-side application?
5. Is this problem just seen with one INA220 on multiple boards? Or is this problem seen with multiple INA220 on one board?
6. What temperature is the board being heated up to?

Sincerely,
Peter Iliya
Current Sense Amplifiers

Hi Peter,

thank you for your reply!

for your questions:

1. What is the Vbus voltage?

---it is 48V divided down to around 9V, and the capturing result shows it is stable. 

2. Is the shunt current being measured a PWM signal or is it DC?

----it is DC.

3. Is there an input filter being used?

----there is an input cap of 0.1uF C53, no serial resistor.

4. Is this a high-side application?

----what do you mean high-side?

5. Is this problem just seen with one INA220 on multiple boards? Or is this problem seen with multiple INA220 on one board?

----they manufactured around 3k brds,  1pcs IN220 on one brds, and around 20% brds has such issue.

6. What temperature is the board being heated up to?

----currently I haven't gotten the information yet.  only know the brd is in room temp. 

and we also do some experiment these two days, with a stable input 7mV shunt voltage from external source, the output is still drifting.  and when replace the chip with a new one, the result is good. and the power supply ripply test with 300M BW is only 50mVpp.  now it seems the issue is mainly related with chip.   tomorrow I will go on site to do further experiment.  if I get some failed sample back, where should I send to?  tks!

below is the sch, because customer can not send to us, so only get such blur pic:

1. INA220 sch.  power supply decoupled by 4.7u*2 , 0.1u*1.

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2. Shunt voltage in red circle.

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