OPA544: +Ve power supply not providing

Hi Kumaresan,

so V+ = 0V and Vin = 0V? In this case you would exceed the common mode input voltage range which would mean that your output voltage becomes unpredicted. Even phase reversal could occur. If your load is low, then an unwantedly high output current could flow during this condition.

Kai

Hi Kai,

Yes. Non-inverting input will be 0V.

The circuit as below,

I am using a relay to disconnect the output also but if at all output gets connected to low resistance(by chance), Will it damage the OPA544T device?.

Please confirm.

Kumaresan

Hi Kumaresan,

can you please post the schematic again? It didn't come through. Press the "Insert File" button (paper clip) in the header of text box to do so :-)

Kai

Hello Kumaresan,

Your inquiry "Is there any problem or issue if we didn’t give power for +V but we maintain –V for OPA544T and will not give any input signal also during this time? we don’t expect to OPA544T as working during this time But would like to know whether the device will be damaged or not."

It sound like you are proposing to let the OPA544T +V float (high impedance) while -15 V is being applied to -Ve? The OPA544T, like all TI op amps, are designed and intended to have both power supplies applied at the simultaneously. Leaving one supply pin floating while the other is powered is a recipe for a potential internal latch condition. This may result in excessive current flow through the device following unexpected paths (like high current flowing out an input pin, or output pin seeking a path to ground), or even device damage. We do not recommend powering any op amp in the manner you propose.

If you must have one supply powered for some time before the other usually a safe way to do that is to include transient voltage suppressor (TVS) diodes from each supply pin to ground as seen below in the accompanying image. The inclusion of the diodes assures a complete current path is provided between the op amp power supply pins and current can flow through the op amp internal circuits.The op amp probably isn't powered for normal operation, but the current flow between the supply pins should help prevent latching from occurring.

The TVS diodes should have a voltage breakdown rating several volts beyond the op amp's intended operating voltage to assure they don't turn on during application of the intended supply levels.

Regards, Thomas

Precision Amplifiers Applications Engineering