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LMZ31530: Regulate Output with PVIN variation

NIKUNJ Zadeshwariya
Prodigy 20 points
Part Number: LMZ31530
Other Parts Discussed in Thread: TPS60151

I would like to use LMZ31530 for FPGA supply with 0.9V rail output. My concern is with its output regulation. Output is adjustable with Vadj Pin(by connecting single Rset resistor to AGND) and it is dependent on PVIN input voltage. My application works on battery and hence PVIN may vary with discharging of battery (Variation is 4.2 to 3V). And hence output will also change accordingly. Would you please suggest or clarify how would i make sure that output remains constant with PVIN Variation?

  • 0
    TI__Guru 50120 points

    Hi Nikun,

    The LMZ31530 has an option to use PVIN and VIN seperately. PVIN can go as low as 3.0V but VIN must be greater than 4.5V to power internal control circuits.If you are wondering how to provide a stable input voltage to prevent any PVIN variation that would affect your output regulation, you can provide a stable 5V input by connecting your "variable voltage source" to the charge pump(TPS60151), tie PVIN and VIN together on the LMZ31530, and connect the 5V input supply voltage to PVIN/VIN pin. This way your conversion will always be 5V to 0.9V or whatever adjustable output voltage option you want to use. 

    LMZ31530_BatteryInputVariation.pdf

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Prodigy 20 points

    Hi Jimmy,

    As VIN requires min 4.5V and i'd have only 3.0V battery supply i can not connect both together. But yeah i think by providing stable input via TPS60151 to VIN and connecting battery to PVIN should work. 

    Thanks for the explanation. :)

    Regards,

    Nikunj