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PTH12000W: Voltage drop appears after 20 ms when turn on.

Daniel Osorno
Prodigy 10 points
Part Number: PTH12000W

Name of device: PTH12000W

Test made: Turn ON without load (the same voltage drop appears when load is 0 to 1.5 A of load, although if the load is higher, the voltage drop is lower.). By using a load of 2 A, the voltage drop disappears.

Fig 1: Turn ON with no load. (yellow) Vin = 12 V, (green) Vout = 3V3

Fig 2: Detail of the glitch which appears 20 ms after the turned on without load. (yellow) Vin = 13.2 V, (green) Vout

This voltage drop of 300 mV appears without load (0 to 1.5 A) by using different configurations:

-          Cout = 33 uF + 100 uF + 100 uF (Cin = 47 uF + 47 uF)

-          Cout = 33 uF + 100 uF (Cin = 47 uF + 47 uF)

-          Cout = 33 uF (Cin = 47 uF + 47 uF)

-          Cout = 0 (Cin = 47 uF + 47 uF)

-          Cout = 330uF (Cin = 47 uF + 47 uF+ 330uF)

 

We need to remove this voltage drop because for our application is not acceptable (from 3V3 to 3V0).

Why this voltage drop appears? Is there any way to remove that?

 

Thanks in advance.

  • 0
    TI__Mastermind 38230 points

    Daniel:

    PTH12000W during start-up  Vout  for the first 20-25ms is under pre-bias control. . Pre-bias startup condition occurs as a result of an external voltage being present at the output of a power module prior to its output becoming active. This often occurs in complex digital systems when current from another power source is back-fed through a dual-supply logic component, such as an FPGA or ASIC.  

    Is it possible to possible to pre-load PTH12000W to about 2 amps.

    If there are any further questions, my direct e-mail is tguerin@ti.com

    Tom