INA180-Q1: Analog output stuck to 0V

Hello,

No nothing has changed on the INA180. If you could give me the lot number on the Digikey package I can verify if these are genuine parts.

Has anything else changed in your circuit? If you power-cycle the board does the issue persist? Would it be possible to verify the VS voltage and VCM voltage on a scope shot (during power-up with and without failure)?

Regards,

Cas

Dear Cas,

thanks for your feedback.

Please find here below all the measurements - with and without failure.

SCREEN 1 - WITH RESISTIVE LOAD CONNECTED - NO FAILURE

CH1: INA180 - Pin 4 - IN- (YELLOW)

CH2: INA180 - Pin 3 - IN+ (BLUE)

CH4: INA180 - Pin 5 - VS (GREEN)

The IC supply line (+5V) is up ~2 seconds before activating the output power line (+12V)

SCREEN 2 - WITH RESISTIVE LOAD CONNECTED - NO FAILURE

CH1: INA180 - Pin 4 - IN- (YELLOW)

CH2: INA180 - Pin 3 - IN+ (BLUE)

CH4: INA180 - Pin 1 - OUT (GREEN)

At the beginning the output is high saturated, and after 40us if works nominally

SCREEN 3 - WITH RESISTIVE LOAD CONNECTED - NO FAILURE

CH1: INA180 - Pin 4 - IN- (YELLOW)

CH2: INA180 - Pin 3 - IN+ (BLUE)

CH4: INA180 - Pin 1 - OUT (GREEN) FILTERED, post RC (R101, C69)

The RC filter works fine, filtering the OUT signal.

SCREEN 4 - WITHOUT RESISTIVE LOAD - NO FAILURE

CH1: INA180 - Pin 4 - IN- (YELLOW)

CH2: INA180 - Pin 3 - IN+ (BLUE)

CH4: INA180 - Pin 1 - OUT (GREEN)

The output signal gets low after the 10uF capacitor is charged - no load is connected.

SCREEN 5 - WITHOUT RESISTIVE LOAD - !!FAILURE!!

CH1: INA180 - Pin 4 - IN- (YELLOW)

CH2: INA180 - Pin 3 - IN+ (BLUE)

CH4: INA180 - Pin 1 - OUT (GREEN)

Error condition: the OUT signal stays high for more than 40us, and then slowly goes to 0V. The external load is not connected. 

The two plots have different time scaling, in the second plots you can see the output discharge phase.

Please note that in this condition the Vs is up way before the external load is powered. 

Thanks,

Andrea

Regarding the missing information:

• No, our design didn't change in the last 3 years. We are now checking the passive components with respect the previous production batches, but all the relelevant components are the same.
• If we power-cycle the board, it's like flipping a coin: sometimes the fault condition happens, but it seems random.
  
  
• The IC marking is the following:

Do you need more info about the DigiKey part?

Thanks,

Andrea

Hello, 

Yes if you can provide the lot number on the digikey esd bag label there should be a lot number. 

Also is it possible to get a Vs with IN+ and IN-  and a failure you show here Vout?

I will look this over.

Regards,

Cas

Dear Cas,

here the DigiKey info:

In case of failure, the Vs is stable and high (+5V) some seconds before the +12V are applied to the load.

 With respect to SCREEN 5, the Vs has the same behaviou shown in SCREEN 1.

Hello,

Okay there are problems with latch-up when the device has a floating Vs and a Vcm is applied I just wanted to check this was not happening. I will continue to look into this problem and the authenticity of the INA180. Expect a reply within the week.

Regards,

Cas

Hello,

It looks like the common mode when there is a failure goes from ~2.7V to 12V while on the no failures the Vcm goes from 0 to 12V. What is 12V_PTC rail powering? 

Regards,

Cas

Hi there,

12V_PTC rail powers two external pressure sensors (the nominal current absorbed for the two sensors is ~5mA). The 12V_PTC rail has also a 10uF bypass capacitor.

Understood your point on the ~2.7V starting voltage: we now double check the Vs voltage.

Thanks,

Andrea

Hello,

The top markings are correct on the part so they most likely are genuine parts. Let me know about the 2.7V on the common mode for the failure.

Regards,

Cas