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TPS7A4501 minimum delta v?

Mauro Kerry
Prodigy 115 points

I am using a TPS7A4501 as an adjustable regulator for a noise sensitive LF power amp.  The input voltage is 8.5 volts from a switching pre-regulator.  When the output voltage is less than 7.4 volts the wideband output noise is 2mv or so.  When the output voltage is increased above this value to about 8.14 volts a 7mv pp oscillation of about 25KHz appears on the output.  I have done test into a 10 ohm resistive load and the same thing occurs.  Does this regulator have a problem with delta v's less than 300mv ?

Kerry  

  • 0
    TI__Genius 15780 points

    Hi Kerry,

    From the datasheet: "Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current."  At 300mV, the device is close to its dropout voltage at full load (1.5A) and the device may not regulate as well.  With an RLOAD of 10ohms, the device is still operating at 0.8A and the dropout voltage should be similar.

    What output capcitance do you have on the device?  A higher output capacitance may help in reducing the noise.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Prodigy 115 points
    Thanks Alek,

    I should have read the data sheet a little closer. I'll try to raise my input voltage a little higher to see if that fixes it.

    Kerry