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Original question:

LM5170-Q1: LM5170-Q1: External gate driver(UCC27712DR)

LM5170-Q1: LM5170 Vin pin current calculate

user5339996
Prodigy 80 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: LM5170

Dear experts,

Because my input voltage maybe exceed over 100V, I want to use linear regulator to limit input voltage in LM5170.

I need to know vin pin current to design resistor and power dissipation.

Zener diode is used to 85V. 

thank you

BR

Steven

  • +1
    TI__Guru 68675 points

    Hi Steven, 

    Thank you using the Lm5170.  The total current into the VIN pin is less than 375uA + the current draw by the RAMP circuits, which are two RC circuits discharged each switching cycle.   

    Since you input is >100V, just protecting the VIN pin is not enough,  because the SW as well as HO and HB may also exceed their max rating.  You will have to use external half-bridge drivers of >100V rating.  

    Thanks,

    Youhao Xi, Applications Engineering