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LM76005: LM76005RNPR protection Behavior

Red Yen
Expert 4360 points
Part Number: LM76005

Hi Support team 

my customer would like to adopt LM76005RNPR in our power supply.

The input voltage of this IC is +48Vdc and the output voltage is +12V/3.5A (for our fan circuit).

 

some questions about the IC behavior when do a single fault as below items.  (see below circuit)

  1. What is the IC behavior when we do the short circuit across the RFBB? 
  2. What is the IC behavior when we do the open circuit across the RFBT? 
  3. What is the IC behavior when we do the short circuit across the PVIN and SW pin, it seems like we short the High Side MOSFET inside the IC? 
  4. What is the IC behavior when the voltage at FB pin is over 115%? Will it turn off the High Side MOSFET and Turn ON the Low Side MOSFET at the same time?

 

For item 1 and 2, Does it require an external OVP circuit to pull down the EN pin of the LM76005RNPR when the OVP occurs?

Please advise.

  • 0
    TI__Expert 4821 points

    Hi Red，

     Ⅰ. Ⅱ. In my opinion， both 1. 2. means FB short to GND. Shorting FB to GND will cause no voltage regulation control. It won't damage LM76005 itself. But the un-regulated output voltage may harm other device in your system.

    Ⅲ. If you do the short circuit across the PVIN and SW pin, LM76005's Low side FET will be damaged.

    Ⅳ. Did 115% have some special meaning? A high FB voltage will lead to a lower duty cycle. But it doesn't mean LM76005 will turn off the High Side MOSFET and Turn ON the Low Side MOSFET immediately.

    Ⅴ. It depend on the requirements of your load. I'm not sure about how fast the OVP need to be.

    BR,

    Victor

  • 0
    TI__Expert 4821 points

    Hi Red,

      I'll close this thread according to forum rules. If you have any other question about this case, please feel free to reply and this thread will be re-opened.

      Thanks.

    BR, 

    Victor