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LM61495-Q1: Damage in surge test

Part Number: LM61495-Q1
Other Parts Discussed in Thread: LM61495

Hi Team,

My customer now use LM61495 in their design. During 500V surge test, the TVS did not burn out. The LM61495 has the following two situations:

(1) When the LM61495 is connected to a load (normally installed, 正常装机), the LM61495 will be burned out;
(2) When the LM61495 is not connected to the load (a separate power supply board, no load单独电源板,没有负载), the LM61495 will not be burned out.
Customer also measured with an oscilloscope that TVS can clamp the voltage at around 32V during the surge test, but the negative pulse voltage will also reach -30V.

Since the absolute maximum rating of 61495 is -0.3 to 42V, I guess because the negative pulse voltage is -30V, so LM61495 is damaged? Could you kindly check any advice about this?
The circuit is shown in the figure below.

  • Hi,

    When you measure the VIN pin to GND pin, is the voltage measurement -30V? If so, this is outside of the minimum input voltage rating of the VIN pin and may result in damage. 

    Refer to Section 7.1 (Absolute Maximum Ratings) of the datasheet which specs the transient and continuous VIN to AGND/PGND is -0.3V. 

    You can place a diode in series with the input path to VIN pin to try and prevent that from happening.

    Regards,

    Jimmy 

  • Hi jimmy,

    Customer already add LM74700 protect anti-reverse before 61495.

    The -30V mentioned before is the power input terminal, not the VIN near the LM61495.

    The VIN waveform of LM61495, customer will measure it next time to see if there is any negative pressure.

    If a negative voltage (like -30V) is applied to the VIN of the LM61495, will it burn out the chip? What will happen?

  • Hi,

    It is specified in the datasheet that anything beyond the range listed in the absolute max rating may have damage to the device.

    As such it is suggested to stay within this rating.

    Regards,

    Jimmy