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LM74502: EN pin and UVLO pin

Rob
Prodigy 130 points
Part Number: LM74502
Other Parts Discussed in Thread: LM74900-Q1, LM74912-Q1, LM74912Q1EVM

Tool/software:

Hello,

I would like to use the LM74502 to protect my circuit from a 12V power supply.

I need to cut off the 12V power supply in case of undervoltage and overvoltage. But I need to be able to control the activation of the 12V via a 5V signal.

The ideal would have been to have a separate EN pin and UVLO pin and not a pin for both functions.

Do you have any assembly ideas to be able to control the LM74502 while retaining the under voltage function?

Or another component that could be suitable for my application?

Thanks in advance,

Rob

  • +1
    TI__Mastermind 46170 points

    Hi Rob,

    Please consider using LM74912-Q1 or LM74900-Q1 in which EN and UVLO pins are separate.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 130 points

    Hello,

    Thanks for your reply.

    I will use the LM74912-Q1.

    1. The "SW" pin is defined as an input. Isn't it an output?

    2. Can the "SW" pin support a 2mA current drawn by my voltage dividers (UVLO and OV)?

    3. Can the "SLEEP_OV" pin be connected to GND if it is not used?

    4. I am not using the SLEEP function. I enable the LM74912-Q1 via a 5V signal. Is this connection correct?

    Regards,

    Rob

  • +1 in reply to Rob
    TI__Mastermind 46170 points

    Hi Rob,

    1. SW pin can be considered input/output pin. Input because it senses voltage from A pin and output because it feeds voltage to resistor ladders. It should affect the designs.

    2. Yes, it can support 2mA current.

    3. Since, you dont need sleep function, you can connect it to either VS or VOUT and its functionality will never come into picture. Connecting SLEEP_OV to OUT should be the easiest way out as they are adjacent pins. 

    4. If you do not need sleep function, you can tie it high. Connecting it to EN should be fine.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 130 points

    Hello,

    Thanks for your reply.

    1. If the EN pin is at 0V (via external command), does the LM74912-Q1 protect against negative voltage (-65V)?

    2. I do not use the FLT# pin, can I connect it to GND (so as not to leave it floating)?

    3. Can I connect the NC pins to GND (so as not to leave them floating)?

    4. The CAP capacitor is connected differently in the evaluation kit (LM74912Q1EVM) [schematic: sheet 10] and in the device datasheet [schematic: sheet 21]. In the datasheet, CAP is connected to pin C, but in the evaluation kit, CAP is connected to pin VS (on the other side of the Rvs resistor). How do I connect this capacitor?

    Regards,

    Rob

  • +1 in reply to Rob
    TI__Mastermind 46170 points

    Hi Rob,

    1. Yes, it will protect.

    2. Yes, you can ground it.

    3. Yes, you can.

    4. Please connect CAP to VS pin.

    Regards,

    Shiven Dhir