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ALM2402-Q1: Thermal shutdown and safe operating temperature related

Josh Wei
Intellectual 1197 points
Part Number: ALM2402-Q1
Other Parts Discussed in Thread: ALM2402F-Q1, ALM2403-Q1

Hi, 

Please help me with these questions related to thermal and temperature of ALM2402-Q1.

  1. at section 7.3.5, how to understand the safe limits and thermal shutdown hysteresis? Is there a specific number of these values? 
    1. In my understanding, the safe limit is TJmax 150℃, from the TJmax to OTF is the hysteresis, is that right?
    2. How long can the device works in this region?
  2. How to understand "The op amp toggles on and off between the thermal shutdown hysteresis", do you know how to shutdown these devices safely when thermal shutdown occurs. In the other word, I want to turn off this device with a specific signal.
  • 0
    TI__Mastermind 23210 points

    Hey Josh, 

    Our Applications Engineer who knows this device well will be back on Monday. For now I will try to answer some of the questions the best I can. 

    Josh Wei said:
    In my understanding, the safe limit is TJmax 150℃,

    The absolute maximum die temperature is 150 degrees C. However please note the footnote in the datasheet below. 

    Josh Wei said:
    Is there a specific number of these values? 

    The typical hysteresis is approximately 7-10 degrees. 

    We will look further into the details of your question and provide some feedback by the end of business on Monday. 

    Best Regards, 

    Chris Featherstone

  • +1
    TI__Guru 56891 points

    Hi Josh,

    Josh Wei said:
    do you know how to shutdown these devices safely when thermal shutdown occurs. In the other word, I want to turn off this device with a specific signal.

    First of all, ALM2402F-Q1  or ALM2403-Q1 is the resolver driver. ALM2402-Q1 has certain limitation for resolver application, since its full power BW is not high due to the low slew rate.  

    In ALM2402F-Q1, the OTF/SH_DN pin has dual functionality. If the internal thermal shutdown is occurred due to elevated Tj temperature, the OTF pin's voltage will pull low (< 0.4V) from the internal overtemperature circuitry. At the same time, SH_DN pin can pull low to shutdown the output (from low impedance to high impedance) with an external circuitry, such as the pin is driven by GPIO from MCU/DSP processor. The OTF/SH_DN pin is how you would shutdown the driver safely, if some desired or undesired events are commanded or detected. 

    Typically, resolver's overcurrent or short output current conditions can result the ALM2402F-Q1/ALM2403-Q1 into overheating or high heat dissipation conditions, where the internal Tj is rising and cause the IC's internal thermal detection circuitry to be activated - this is the IC's default self thermal protection feature. If the design requirements have current sensing circuitry and would like to use the status to activate OTF/SH_DN pin, you may certainly do that. Since I do not know your customer's specific fault conditions to be protected, I am unable to provide the details recommendation for the application. 

    If you have other questions, please let me know. 

    Best,

    Raymond 

  • 0 in reply to Josh Wei
    TI__Guru 56891 points

    Hi Josh, 

    Are there any inquiries that we missed? 

    If you have resolver's design requirements, I can simulate the whole circuit for you, if you are interested. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Intellectual 1197 points
    Chris Featherstone said:
    Josh Wei said:
    Is there a specific number of these values? 

    The typical hysteresis is approximately 7-10 degrees. 

    We will look further into the details of your question and provide some feedback by the end of business on Monday. 

    This question please

  • +1 in reply to Josh Wei
    TI__Mastermind 23210 points

    Hey Josh, 

    The thermal shutdown temperature is listed in the product datasheet with a typical of 165 degrees F. The hysteresis is typically 7-10 degrees based on measured data. 

    Best Regards, 

    Chris Featherstone