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GD75232: The operation temperature for GD75232

Zhang Liang
Expert 2745 points
Part Number: GD75232

Hi,

We use the GD75232 for the RS232 driver in the product,  we measure GD75232 surface temperature is more than 80℃ when power on, but the RS232 commuincate is normal;

Now, we have no idea if this temperature is normal or abnormal;

We temporary determinate the temperature is abnormal, and we we test GD75232 circuit as below step:

1. We remove the load, the temperature is also more than 80℃ and there are no improve;

2. We continue remove the input signal circuit, we only reserve +/-12V VDD/VSS power(On board) input in and GND, the temperature is also more than 80℃ and there are no improve;

3. We use the external +/-12V VDD/VSS power input and GND(Off board), the temperature is also more than 80℃ and there are no improve;

4. We only use the +12V VDD power input and GND, and the input current of VDD is 2.6mA; And we add -12V VSS and the input current of VDD is 10.7mA(The normal current in datasheet is 5mA max.);

5. We have no idea that how to solve the issue, pleaes kindly help, thanks.

The schemaitc diagram please refer to below:

  • 0
    TI__Mastermind 46607 points

    Zhang,

    What is the ambient temperature of the test - not surface temperature of IC? 

    When measuring IDD current are all the inputs floating? Our test condition specifically states an input voltage which doesn't seem to be adhered to in this test - you can and most likely will see higher currents if the inputs are floating. 

    Are there any communication issues or is the concern that the surface of the device is 80C? 

    Have they followed the power sequencing described in datasheet during testing?

    Ultimately the junction of the device is what is most important when considering thermal considerations. Varying with package the ambient temperature + thermal impedance * power dissipated needs to remain under 150C degrees. The thermal impedance will change based on package.  In the test setup that you have shown - I don't think you are hitting that limit. We spec a max ambient temperature of 70C - but the internal junction can heat up to 150C before damage occurs - we just don't guarantee performance after 70C ambient has been crossed. 

    Please let me know on the above questions - but you may not actually have an issue - if you confirm the above questions I will be able to give you more confidence if there is an actual issue or not. 

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Expert 2745 points

    Hi,

    We test the IC on the laboratory the temperature is 25℃;

    We test the IDD current all the inputs floating, the result is same as on board when we connnet the signal pins;

    There are no communication issue when the surface temperature above 80℃;

    The VDD(12V) and VSS(-12V) are the synchronous power on, but we turn the 12V first and then ture the -12V, the result is same;i

    I know the 150℃ Operating virtual junction temperature is the max. in the datasheet, and we want to know if the 80℃ surface temperature is normal or not?

    And we use a new GD75232 IC to repeat this testing, the result is same as the last one. 

    So please kindly recommend how to solve this issue, or can you test on your laboratory also? Thanks.

  • 0 in reply to Zhang Liang
    TI__Mastermind 46607 points

    Hi Zhang,

    Okay - so the surface temperature does not matter - only the junction temperature does and the ambient since we do spec a max ambient temperature.  

    Your test condition isn't exactly the same as ours for IDD current - so you can't say we are out of spec because you are using testing the device in a different setup. Test conditions must be followed exactly - you can't apply the same specification to different test setups and expect the same performance. 

    The junction temperature is found with the following equations:

    where i represents the pin number and N representing the total number of pins on the device. The power dissipated is the sum of the product of voltage and current at every pin. So that needs to be measured at every pin to get a power dissipation approximation on the device 

    The junction temperature is a function of ambient temperature and thermal impedance - which is listed in the datasheet and varies by package - but also will vary in system level. 

    If the TJ stays under 150C and the TA stays at or below 70C there is no issue. 

    Since there are no communication issues, your test conditions don't match with what we spec - so there is no indication of device issue, surface temperature is not specified anywhere in our datasheet - I don't see any issue and there is no current reason to believe the part is malfunctioning.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Expert 2745 points

    Hi,

    We only connect the VDD and GND, the surface temperature is less than 40℃, but if will rise to 80℃ when to connect to VSS, so we wants to know if this temperature is normal or not? 

    Based on your comment, our IDD test condition isn't exactly the same as yours for IDD current, so please advise how to test the IDD current, and we can test the IDD by ourselves and provide to your to compare, thanks.

  • 0 in reply to Zhang Liang
    TI__Mastermind 46607 points

    Zhang,

    There is no issue to help you with. Your part is fine - unless there is an actual issue I can't help you. I have given you everything I can at this point. The test conditions are listed right next to spec - but once again there is no issue here. The device is heating up because of the power its dissipating but that is okay you aren't having communication issues or signs of damage. 

    Best,

    Parker Dodson