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LMZ35003: Start Up Delay Circuit Question

KevinZhang123
Expert 5750 points
Part Number: LMZ35003

Hi, Team

My communicaiton customer is using LMZ35003 in their smart antenna products, to convert 12V to 10V. They want to delay the LMZ35003 start up.

As LMZ35003 is first stage power converter, no MCU can control the INH/UVLO pin. They use 599kohn and 91kohm resisters as voltage divider on INH/UVLO pin, and place a 4.7uF capaciter between INH/UVLO pin and GND to delay the start up.

1. Is there any potential risk if adding 4.7uF capacitor on INH/UVLO pin? Will it affect the INH/UVLO function?

2. Is there better solution to delay the LMZ35003 start up?

Thanks

Kevin

  • 0
    TI__Guru 50120 points

    Hi Kevin,

    From the resistor divider(Ruvlo1 = 599kOhm and Ruvlo2 = 91kOhm) they will have a Von of 9.47V using equation 3 of the datasheet. The recommended way to delay the startup is by increasing the Von threshold. Placing a capacitor on the INH/UVLO is another method to delay the startup and will not affect the INH/UVLO function. 

    Regards,

    Jimmy