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TPS7A92: Thermal shutdown behavior and other recommended device

Ryotaro Fukui
Intellectual 2345 points
Part Number: TPS7A92
Other Parts Discussed in Thread: LMZM33602EVM, LMZM33602

Hello team,

I received a question from my customer about thermal shutdown of TPS7A9201DSK. I would appreciate it if you could provide us some advice about the following 3 questions.

◆ Environment

Assumes input 3.3V/output 1.2V, load current up to 1.561A or less.

◆ Questions

(1) When using the maximum current value in the above situation,  it is likely that the junction/case temperature would exceed 200°C at an ambient temperature of 25°C.

The data sheet confirms that ThermalShutdown will function at approximately Typ160°C before reaching this temperature.

When the temperature exceeded shutdown temperature threshold, does this IC turn off and drops the output voltage (output Enable off?) immediately? Or does it have some delay time?

(2) Are there any pin compatible device for TPS7A9201DSK that the junction temperature is within the operating temperature range under the above conditions

(3) If there are no devices that meets question 2, they would like to place the Buck Converter EVM, which has an input voltage (DC) of +24V, an output voltage of 1.8V, and a maximum load current of 1.561A, in front of the TPS7A9201DSK.

The current candidate is LMZM33602EVM. Are there any other EVM candidates with a lower price and a smaller area?

Best Regards,

Ryotaro Fukui

  • +1
    TI__Genius 12365 points

    Hi Ryotaro, 

    You are correct, if using Tj=Ta+(Rja*Pdo) and using your presented scenario, then, Tj=25C+(56.9C/W*3.27W)=211C.

    However, I would like to mention that this is a rough estimate and it does not mean that the device will reach such high temperatures due to the Thermal Shutdown.

    When the device heats to 160C, then Thermal Shutdown occurs, meaning that the device will completely shut down Output=OFF. The device will reset (turn on) when the Tj~140C. Since the thermal time-constant of the semiconductor die is fairly short, the output will turn on and off until power dissipation is reduced. 

    There are devices in our portfolio that can handle really high temperatures, unfortunately, they are not P2P. The majority of our devices have absolute maximum ratings of -55C to 150C and the Recommended Operating Conditions are: -40C to 125C.

    I would like to highlight the importance of the PCB design for thermal performance. If the PCB is properly designed for heat dissipation, then your device might not enter Thermal Shutdown. Another recommendation is using heatsinks if customer thinks this might be an issue. You can follow this Application Notes for further reading and understanding the impact of PCB design on LDO thermal performance :

    "An empirical analysis of the impact of board layout on LDO thermal performance"

    Regarding the Buck Converter LMZM33602, I can redirect you with that group for proper and further recommendations.

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    TI__Intellectual 2345 points

    Hi Edgar,

    Thank you for explaining us about thermal shutdown. It was easy to understand and very helpful for me and the customer.

    And about the LMZM33602EVM, if possible, they wants to know the board size of the LMZM33602EVM in addition.

    Also, as an alternative to the LMZM33602EVM, they told that it is desirable if the input voltage, output voltage, output current, and output noise level are equal to or less than the LMZM33602EVM.

    Thank you for the continuing support.

    Best Regards,

    Ryotaro Fukui

  • 0 in reply to Ryotaro Fukui
    TI__Genius 12365 points

    Hi Ryotaro, 

    It is good to know the thermal information was useful.

    Unfortunately, I do not have the information for the board size of LMZM33602EVM. This device corresponds to another family of devices. 

    We will need to reassign this forum post to the owners of the LMZM33602 device family. 

    Thank you for sharing your information with us. 

    Best, 

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    TI__Intellectual 2345 points

    Hi Edgar,

    I noticed that it is a different device family. For more information on LMZM33602EVM, I will post a new question in a separate thread. I will ask the LMZM33602EVM replacement device (question 3) there.

    Therefore, I would like to close this thread for now. Thank you for your support.

    Best Regards,

    Ryotaro Fukui