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OPA548: I would like to have the schematic of the die that makes this part. In the old days that used to be available.

Robert Kilpatrick
Prodigy 130 points
Part Number: OPA548

We are concerned that our simulation does not represent or indicate a failure we are having sow we want to see the schematic of the die and maybe simulate that or at least use it to analyze the failure we are seeing.

  • 0
    Guru 140200 points
    Hi Robert,

    what failure are you seeing?

    Kai
  • 0
    TI__Guru* 93105 points

    Hi Robert,

    TI does not openly share die images, or detailed die schematics, due to the proprietary nature of many designs. Some general information such as a die image may be included in the datasheet if the product is offered as an unencapsulated die. Also, some datasheets do provide a simplified schematic for the product. That is not the case for the OPA548.

    The best option as Kai mentioned is to provide us information about the OPA548 failure you have experienced. We will need to see your circuit schematic, power supply voltages, input signal details, and output load conditions on the op amp. More information may be needed if we can't make a determination from what is initially provided.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to kai klaas69
    Prodigy 130 points
    I cannot provide the circuit at this time but I will say the we are getting a spike or current draw on Vcc- or output respectively. We have had the wires going from the Die to the output pins fused open at the output in two cases and at VCC- in one. Replacement of the op-Amp generally resolves the issue. All failures were from same LDC. We have not been able to capture the spike or current draw that causes the problem. We do know that in all cases melting away of substrate around the output transistor on the die occurs possibly indicating all were related to an increased current draw on the output pin.Have you had an issue with this die?
  • 0 in reply to Robert Kilpatrick
    Prodigy 130 points
    Output goes to a 1:1.5 transformer
  • 0 in reply to Robert Kilpatrick
    TI__Guru* 93105 points

    Hello Robert,

    The OPA548 is a very popular TI power op amp that provides reliable operation when properly applied and protected. Can you tell me anything about the output load after the 1:1.5 transformer? Back EMF can be an issue with reactive loads and when that is the case external protection of the op amp is necessary. Datasheet Figure 38, Motor Drive Circuit, shows how current steering diodes are used to protect the OPA548 from back EMF generated by the motor. Today, we would add TVS diodes to the power supply pins to provide a current path for current associated with the EMF event.

    Any information you can provide would be helpful.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Prodigy 130 points

    Output load of failure is a .01 uf and 45 ohm resistive load in parallel in a test environment and we have the diodes in like the motor drive circuit

  • 0 in reply to Robert Kilpatrick
    Prodigy 130 points
    We have a 40k and .01u in parallel to our negative rail (-V, -25V) directly tied to ILIM if there was a spike here could that cause a failure?
  • 0 in reply to Robert Kilpatrick
    TI__Guru* 93105 points
    Hi Robert,

    A parallel 45 Ohm resistor with a 10 nF capacitor coupled through a 1:1.5 transformer likely wouldn't present a potentially damaging load. It might present a load that could cause the OPA548 to become unstable. A lot depends on what the transformed impedance looks like at the OPA548 output pin.

    Would it be possible for you to share the OPA548 portion of your circuit schematic so that we can see exactly how it is being configured? Also, it would be really helpful if you can provide the input waveform information, the supply arrangement and what the expected output waveform is supposed to be.

    Thanks, Thomas
    Precision Amplifiers Applications Engineering
  • 0 in reply to Robert Kilpatrick
    TI__Guru* 93105 points
    Hi Robert,

    That ILim connection should be okay for the OPA548, and not cause a failure. The internal current limit circuit is located prior to the output devices, in a low current portion of the circuitry.

    Regards, Thomas
    Precision Amplifiers Applications Engineering
  • 0 in reply to Thomas Kuehl
    Prodigy 130 points

    Do you have a group that handles NDA’s

  • 0 in reply to Robert Kilpatrick
    TI__Guru* 93105 points

    Hello Robert,

    Our applications support of the Precision Amplifiers e2e forum is mostly of a technical nature and we don't have involvement in establishing an NDA between TI and our customers. I suggest that you contact the TI field office in your region, or the authorized TI distributor from who you purchased the OPA548 devices and ask them about what is required to have an NDA put in place between your company and TI. They should also be able to check if an NDA is already in place between the two companies. If so, that makes exchanging confidential information much easier and faster.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Robert Kilpatrick
    Guru 140200 points

    Hi Robert,

    is the OPA548 an original TI's component? Or could it be a conterfeit? Have you bought the OPA548 from an authorized TI's distributor?

    Connecting a transformer to the output of an OPAmp can be tricky. A transformer can present a short circuit at DC. Have you AC coupled the transformer to the output of OPA548? Also, have you mounted the Zobel network as recommended in figure 38 of datasheet?

    Are you sure that the OPA548 is not oscillating? Does it become hot?

    Inductive kick backs can easily destroy the output of an OPAmp, if not protected. Have you mounted the free wheeling diodes very close to the OPA548 pins? And don't foget the TVS across the supply terminals of OPA548 as suggested by Thomas!

    Can you insert an isolation resistor at the output? This could decouple a bit the complex load from the feedback loop of OPA548. And it could be used to provide a robust two stage free wheeling protection.

    Kai

  • 0 in reply to kai klaas69
    Prodigy 130 points

    We have the motor diode in but how are the TVS diodes your talking about placed in the circuit, is there a diagram?

  • 0 in reply to Robert Kilpatrick
    Guru 140200 points

    Hi Robert,

    Thomas has explained it here:

    e2e.ti.com/.../2811672

    and here:

    OPA541: Damage at startup with an inductive load - Amplifiers forum - Amplifiers - TI E2E support fo...

    e2e.ti.com
    Part Number: OPA541 Hello, I'm using the OPA541 and at startup the sense input is dammage I drive an inductive load (25mH 2,4ohms) here is the schematic used

    Kai

  • 0 in reply to Robert Kilpatrick
    TI__Guru* 93105 points

    Hello Robert,

    Kai referenced the TVS drawing posted to an earlier E2E inquiry. It is fine, but here is an updated, more complete version of that drawing. Hopefully this will make the protection circuit connections more clear.

    Regards, Thomas

    Precision Amplifiers Applications Engineering