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UC2845: UC2845 operation temp range

Given Ding
Genius 10115 points
Part Number: UC2845

Hi,

here is a question from customer in RRU application

1. recommended operation condition in datasheet shows Ta spec is -40C to 85C.

2. absolute maximum rating in datasheet shows Tj spec is up to 150C

In customer's application, its board temp is ~95C.  So want to check on below:

1. can the part work in above case?

2. if we can secure the Tj to below 150C, can it support long time reliability?

3. many other TI device indicate recommended Tj to be within 125C, is it same for this device?

Thank you

  • 0
    TI__Mastermind 31580 points
    Hi Given,

    If the PCB board temperature is 95C then the pin temperature of the device is known. If you measure the bias current flowing into the VCC pin of the IC and multiple it by the Vcc voltage you can calculate the internal power dissipation within the IC.

    Using the Tjb for the device package you can calculate the junction temperature.

    Note that the electrical parameters for the UC2845 are given for a Ta of 85C which during test equates to Tj of 85C. So if the Tj in the application is over 85C the some of the electrical parameters may outside of the datasheet limits.

    If the junction temperature is kept below 125C then there is no long term reliability issue. Although reducing the junction temperature will always extend the expected lifetime of the device.

    Regards

    Peter