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Original question:

LM7480-Q1: 48V Automotive rail protection (in addition to 12V and 24V rails)

LM7480-Q1: LM7480-Feasiblity for 48V systems

reshma b
Prodigy 120 points
Part Number: LM7480-Q1

Tool/software:

Hi,

I would like to confirm if the ideal diode controller LM7480-Q1 can be used for 48V automotive systems?

I have referred the datasheet LM7480-Q1 Ideal Diode Controller with Load Dump Protection datasheet (Rev. C) and planning to use the circuit as per figure 10-25 application diagram.

Could you please clarify the below points.

1)I need input reverse battery protection of 52V.This means the diode D4 in figure 10-25 needs to be replaced. What is the voltage rating required for D4 in this case.

2)Transient voltage (Load dump) at input can go up to 70V for 40ms.Will this circuit able to meets this?

3)Input voltage nominal range is 36-52V but shall go up to 60V for 1hour.Will this be okay if I chose D1 of 60V.

4)In the datasheet example Q1 is chosen for 200V Mosfet (I understood this is for load dump protection) whereas Q2 is rated for 60V.Whys is it so?

Thanks and Regards,

Reshma

  • 0
    TI__Mastermind 47775 points

    Hi Reshma,

    1. It depends on the level of transients in the system. If the transients do not violate the device ratings, you may not need any diode at all.

    2. Yes, this can be achieved. You just need to scale the OV ladder such that the device ratings are not violated.

    3. Yes, as far as the power rating of Zener is not violated. The series resistor R1 is used to minimize the power dissipation.

    4. This is because the Q1 FET will block any voltage greater than 60V with the help of OV pin. Load dump protection is supported with the help of OV pin only.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 120 points

    Hi Shiven,

    Regarding the diode D4.My  application requires input reverse battery protection of 52V.This means the diode D4 in figure 10-25 needs to be replaced. What is the voltage rating required for D4 in this case. (if clamping voltage needs to be less than absolute max of 65V & breakdown voltage to be greater than 52V we are unable to find a TVS diode part)

  • 0 in reply to reshma b
    TI__Mastermind 47775 points

    Hi Reshma,

    D4 is used to protect the controller and the FETs from negative transients which can be higher than -65V or may stress the VDS of the FETs. Are there any transients which can do the same to your system?

    If not, you don't need any TVS. -52V is something that the controller can withstand without any supporting components.

    Regards,

    Shiven Dhir