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TPS7A8300: Bead suggestion for Input and output

Haritha Munnangi
Intellectual 280 points
Part Number: TPS7A8300
Other Parts Discussed in Thread: ADC12DL2500

Tool/software:

Hi,

ADC (P/N: ADC12DL2500) input regulator for VA11 supply we are using P/N: TPS7A8300,

we are planning to use bead for input and output side for isolation P/N: BLM31PG121SN1L

Input voltage:1.5V

Output Voltage: 1.1V

Load current: 0.9A (Assuming ADC taking)

DCR for bead= 0.04 ohm

Drop voltage after bead V=I*R is 0.9*0.04 =0.036V, then output - drop voltage is 1.1-0.036 =1.064V

So as per this calculation if we place bead at output the voltage can drop to 1.064V instead of maintaining 1.1V, is this bead ok use? or any suggestion for alternate?

Thaks in advance.

Regards,

Haritha

  • 0
    TI__Genius 15125 points

    Hello Haritha,

    Thank you for your question.

    As long as the minimum headroom is met between the input and output voltage, then you should not have to worry about the device heading into dropout.

    Where is the bead located in your schematic, at the input or the output? 

    If at the input, the only concern would be that the input drops below the minimum required headroom. 

    Please let me know when you have a moment.

    Thank you,

    Hannah

  • 0 in reply to Hannah Grace
    Intellectual 280 points

    Hi Hannah,

    Thanks for the quick reply,

    Bead is placing at input side,

    So our input voltage is 1.5V,

    36mV maximum dropout of 1.5V generation IC

    200mv maximum droput of 1.1 Generation IC

    then is it 1.5-0.036-0.2 is 1.264V which is greater than 1.1Voutput voltage

    Is my understanding correct?

    Thanks & Regards

    Haritha

  • 0 in reply to Haritha Munnangi
    TI__Genius 15125 points

    Hi Haritha,

    Since the bead is at the input side, you shouldn't see a drop at the output unless your input is dropping below the minimum headroom.

    As long as Vin is equal to or greater than 0.3V above the output, this device should not head into dropout. 

    1.5V-0.036V = 1.464 input, output = 1.1V. 1.464V-1.1V = 0.364V

    There is a 0.364V headroom between the output and input, which allows this device to avoid heading into dropout. 

    Hope this helps!

    Best,

    Hannah