• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 261 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM74502-Q1: Using as regulator

zabbza
Prodigy 140 points
Part Number: LM74502-Q1

Tool/software:

Dear team,

may LM74502-Q1  be used for surge protection and regulation?

İf a diode connected to input for reverse polarity, Q2 is unneccessary, is that right?

if input voltage is 48 volt and R2 and R3 is arranged to clamp voltage around 30V, Or Dz clamp voltage is choosen 30V, LM74502-Q1 acts like a regulator, is there any unsufficent situation?

which one is sufficient, Arranging R2 and R3 to clamp voltage around 30V or Choosing Dz clamp voltage 30V?

Of course Q1 will be choosed to dissepate  enough power.

 the circuit which is on figure 10-11 on datasheet, is not needed tvs for load dump, Because VS pin is protected with DZ and R1, is that right?

Best Regards.

  • 0
    TI__Mastermind 48085 points

    Hi Zabbza,

    Q2 is present for reverse polarity protection. If you dont require this feature, you can choose to remove it.

    Dz is used to protect the VS pin whereas R2 and R3 will operate the FET to cutoff after certain level and protect the downstream circuits.

    It is true that TVS is not required to clamp the load dump.

    You can refer to EVM for component selection help.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 140 points

    Dear Shiven

    Is above circuit Ok, for regulation and surge protection?

    Best Regards.

  • 0 in reply to zabbza
    TI__Mastermind 48085 points

    Hi Zabbza,

    Please place a zener from GATE to SOURCE. The FET is driven with respect to SRC pin and not ground.11V-12V zener should be enough.

    Rest, the schematic is fine.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 140 points

    Dear Shiven,

    İf A zener (Vz=12V) is placed from GATE to SOURCE, When input voltage is 48V What is the output voltage?

    Are you sure this design(A zener (Vz=12V) is placed from GATE to SOURCE) is work as regulator and output voltage is equal to 30V?

    Best Rgards.

  • 0 in reply to zabbza
    TI__Mastermind 48085 points

    Hi Zabbza,

    No, this will not work as regulator. Apologies I missed it. You need to scale OV ladder such that it cuts-off at 30V.

    You can refer OV ladder to VOUT instead of VIN for hysteretic clamp.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 140 points

    Dear Shiven,

    Main aim is that, Output is limited 30V when input is lower than 60V, and output is cut off when input is higher than 60V

    I do not know inner circuit of LM74502-Q1  so I am not sure.

    When a zener placed gate to gnd as in the picture, Is the circuit output limited to 30V when input is lower than 60V.

    Or can above circuit use to  limit output voltage to 30V when input is lower than 60V.

    Best Regards

  • 0 in reply to zabbza
    TI__Mastermind 48085 points

    Hi Zabbza,

    Please try simulating the above circuit. The model is available on TI.com

    Regards,

    Shiven Dhir