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LM74502H-Q1: Designing with LM74502HQDDFRQ1

Sv
Intellectual 380 points
Part Number: LM74502H-Q1
Other Parts Discussed in Thread: LM74502

Hello Team,
We are planning to use the IC LM74502HQDDFRQ1 for one of our applications.
We have a system which is working from a 12V adapter.
The load current will be 12A maximum.
During wiring assembly, there might be chances the power supply is connected wrong and it may damage the system.
So we are looking for an over voltage and reverse polarity protection.
Can anyone suggest whether LM74502HQDDFRQ1 is a good choice for our application?.
 Supply Voltage = +12V
Load current  = 12A.
Device will 100% time ON.

Can you please suggest a MOSFET as well for the application?.


Looking for the reply.


  • 0
    TI__Mastermind 26025 points

    Hi SV,

    If you don't need reverse current blocking, LM74502 is the right choice.

    For the MOSFET, datasheet talks about MOSFET selection guide.

    Please refer to: "9.2.2.2 MOSFET Selection"

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Intellectual 380 points

    Hello Shiven,
    Thank you for your reply.
    Can you please explain what is reverse current.
    We don't have a battery in the system so may be we don't need reverse current protection.
    Please correct me if I am wrong.
    So like you said, may be we can do with LM74502.
    Also, will it damage the IC when the adapter voltage is reversed?
    The value of the flying capacitor for the charge pup is 0.1uF in BoM and in datasheet while in the application note, it is mentioned as 220nF.
    How to select the value of the flying capacitor?.
    Can you please review the circuit below?.
    The Enable pin is directly connected to the +12V line.
    The over voltage is set to about 13.5V.


    Regarding the MOSFET selection,
    The reference design in the application note is for a load current less than 5A and but they are using the MOSFET DMNH6012SPSQ which has an Id of 50A.
    We have the MOSFET IPTG039N15NM5 in our system.
    Can I use this MOSFET for this circuit?.

    Looking for your reply

  • +1 in reply to Sv
    TI__Mastermind 26025 points

    Hi SV,

    1. Current flowing in the direction shown is called reverse current. Which means if VOUT > VIN the FETs will still be on and provide a path. Whereas reverse current blocking controllers will turn off the FETs.

    2. If the voltage on input side is reverse, the IC will not be damaged. 

    3. Charge pump cap selection is mentioned in the datasheet as follow.

    4. You can use the chosen MOSFET comfortably.

    5. The schematic looks fine.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Intellectual 380 points

    Hello Shiven,
    Thank you for your reply