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LP5912: LP5912-1.5 voltage drop

user4773172
Intellectual 1410 points
Part Number: LP5912

Hi Sir,

We use LP5912-Q1 EVM and change the chip to LP5912-1.5 sample, below is our test results.

LDO

Vin

Loading rise

75mA

150mA

300mA

250mA_400mA

LP5912-1.5

1.8V

0.5us

0.33V

0.43V

0.485V

0.09V

Do you think this voltage drop trend is make sense to you? Is there any way we can improve voltage drop?

Besides, do you have similar size or small size solution and have better performance can promote to customer?

Thank you for your kindly help.

Edward Chen  

  • 0
    TI__Guru 55940 points
    Hi Edward,

    Could you please clarify how you are doing your measurement? Dropout is a DC parameter; therefore, Vin and Iout should be settled before making the measurement. Your measurements look like they could have transient response impacting the results. Could you provide a multichannel scopeshot showing Vin, Vout, and Iout during your testing?

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Intellectual 1410 points

    Hi Ryan,

    I already send a mail to you and attach all pictures.

    Please kindly discussed by mail.

    Thank you.

    Edward Chen

  • 0 in reply to user4773172
    TI__Guru 55940 points
    Hi Edward,

    Thank you for the scopeshots. The scopeshots show the load transient response of LP5912-Q1. Dropout is a DC specification with a constant current and constant load. Load transient curves are provided in the typical characteristics curves section of the datasheet in Figures 32 to 37.

    The load transient response for any LDO will depend on the bandwidth of the LDO, the magnitude of the transient, the slew rate of the transient, and the output capacitance.

    The bandwidth of the LDO is how quick the LDO control loop can respond to the transient. This is not an adjustable parameter as it is a factor of the the design decisions made internal to the LDO.

    The magnitude of the transient and slew rate of the transient are determined by the application. The higher the magnitude of the transient and the faster the slew rate of the transient, the higher the magnitude of the transient response will be.

    The output capacitor will help reduce the magnitude of the transient response while the LDO responds to the transient. The larger the output capacitor, the lower the magnitude of the transient response will be; however, this will also extend the duration of the transient response. This is due to the output capacitor charging/discharging during the transient.

    The following Application Report provides additional details:

    www.ti.com/.../snoa507.pdf

    Very Respectfully,
    Ryan