OPA197: Conditions which could cause large current on power supply pins

Taketo Sato

Part Number: OPA197

Hello team,

My customer uses OPA197 in their product and faced an issue with the circuit.

In customer circuit there is a resistor between OPA197's V+ pin(or V- pin) and positive supply source(or negative supply source). And customer found the resistor somehow failure with OPEN mode.

Customer is now investigating what will potentially cause the resistor OPEN and considers large current flow to OPA197's power supply pins may be one of potential cause.

Could you let me know any conditions which will lead to large current on power supply pins?

Best regards,

over 2 years ago

+1 Marek Lis over 2 years ago

TI__Guru 60590 points

For several reasons, it is not a good idea to include resistors is series with the supply pins:

Any change in the output current (load) will cause modulation of the supply voltage, which in turn may feed into the signal path
The voltage drop across such resistors will affect input and output linear voltage ranges
This may cause a startup issue in low supply voltage applications caused by shoot-through current (spike of current in output stage during power-up)

The series supply resistor may fail if its power rating, P[W], is below OPA197 maximum short-circuit current of 65mA. Since P> V*I = I^2*R, for R=250ohm P>1W.

0 Taketo Sato over 2 years ago in reply to Marek Lis

TI__Genius 9475 points

Hello Marek-san,

Thank you for your comments.

Regarding 3), is the startup shoot-through current a unique behavior for OPAx197? Or is the behavior seen widely with CMOS OpAmps?

Best regards,

+1 Marek Lis over 2 years ago in reply to Taketo Sato

TI__Guru 60590 points

Most op amps exhibit an increase in the quiescent current during power up condition but its magnitude varies depending on the output stage circuit topology used and the ramp up rate in the supply voltage, dVs/dt.

0 kai klaas69 over 2 years ago

Guru 140200 points

Hi Taketo,

can you show a schematic?

Kai

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OPA197: Conditions which could cause large current on power supply pins