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LM7480-Q1: Role of Diode D2 at Figure 10-25

Takeshi Sasaki
Expert 4480 points
Part Number: LM7480-Q1

Hi team,

Could you give me comment on following customer question?

Q1. What is the role of the D2 (85V) at Figure 10-25 in the datasheet? Is it always required?

Q2. Could you tell me how to select D2? 

Best regards,

Takeshi Sasaki

  • +1
    TI__Guru 57737 points

    Hi Takeshi,

    The purpose of D2 is to supply voltage to the VS pin from A pin. The 10 kohms in series with VS pin (which is placed to limit the current into Zener) limits the current required by the charge pump during startup conditions. So, a diode from A to VS provides uninterrupted current into the VS pin.