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Original question:

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

OPA548: OPA548 DC input create thermal rise

Robert Kilpatrick
Prodigy 130 points
Part Number: OPA548

OPA548: We have a situation where we are following a circuit very similar to your Evaluation board SBOU132 (Figure 1) including the "Motor " Diodes (D1/D2) where we have a solid DC voltage going into the inputs of U1. the output has a 1:1.5 transformer across R6/C8 which is probably sinking any output. The reason we have DC is our VDD and VSS PS are left on during test and put about approximately 6.5 VDC on U1-1 and U1-2. When this occurs we get  about 70 DegF rise on the op-amp a jump up from 70 nominal. We are well within the thermal parameters of the op-amp is there any concern about long term stays in this condition?

  • 0
    TI__Guru* 93105 points

    Hello Robert,

    One of the main operating constraints concerning a semiconductor device is the maximum junction temperature Tj(max) specification. For most semiconductor devices, including the OPA548 Tj(max) is specified as 150°C. Operating above that temperature can impact the long term reliability of the device, and the higher Tj is operated at the sooner a failure might occur.

    You mention that your OPA548 is initially at 70°F, or 21.1°C, and then the temperature increases by another 70°F to 140°F when power is required. A  temperature of 140°F is equivalent to 60°C, which I assume is measured some pint on the OPA548 package, or power tab. The important temperature to determine is Tj and whether it is exceeding 150°C, or not. The OPA548 datasheet in Section 11.5 provides useful information that should allow you to calculate Tj for your specific application conditions.

    Do keep in mind that the OPA548 internal thermal shutdown function will activate around 160°C Tj so if it isn't activating, then the the junctions aren't getting that hot. The thermal shutdown function will continually activate at 160°C, and turn then deactivate at about 140°C. This cycle will continue repeatedly if Tj is getting too hot.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    TI__Guru* 93105 points
    Hi Robert,

    Do you have the information you need regarding the OPA548 thermal rise? If so, please close this e2e inquiry.

    Best regards, Thomas
    Precision Amplifiers Applications Engineering