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PTH08T231W : How can we decrease output noise and output current (70mA) when there is no load?

Lewis Kevin
Intellectual 500 points
Other Parts Discussed in Thread: PTH08T231W
Greetings,
We managed to form a DC to DC Convertor circuit using PTH08T231W.
Please check the attached data.
Structures are like below :
input voltage : 12V Linear DC Power Supply (E3632A Agilent)
output : 5V/5A

Question 1. 
Input current is 70mA without a load.
we cannot obtain specifications of output ON condition in Data sheet.
Please check whether this is activating properly.

Question 2.
When there is a load with 5V/5A, ripple is much higher than we expected.
We'd like to have at least 50mV p-p, is this possible?
If it is possible, can external components can be involved?
and how can we make at least 50mV p-p?

  • 0
    TI__Mastermind 38230 points

    Bae Su-min:

    I reviewed the e-mail and your questions concerning the PTH08T231W an output ripple with 12Vin and 5Vout at 5 amps.

    1. The normal  input current with 12Vin and 5Vout with no load is about 77mA.

    2. Figure 1 and 2,are PTH08T231W data below,  is with 12Vin and 5Vout at 5 Amp load. This is output ripple as measured with a 20MHz bandwidth .

    . Fig #1 scope loose coupling at 20MHz bandwidth. Ignore High frequency switching pulses which are stray pick-up scope probe (Ground) . Measures  loose coupling probe not across external  ceramic capacitor

    The ripple is low frequency sinusoidal data at 288kHz. The higher amplitude high frequency switching pulses  on the sinusoidal are from the scope probe sensitivity to e-field noise. They are easily detected when the scope probe has long ground probe connection and clip on center conductor.This is described as loose probe coupling.

     Fig #2 Scope close coupling at 20MHz bandwidth. Ignore High frequency switching pulses which are stray pick-up scope probe (Ground) . Measures  close coupling probe across external  ceramic capacitor reduces stray high frequency switching pulses.

    Close- coupling  The ripple is low frequency sinusoidal data at 288kHz. The higher amplitude high frequency switching pulses  on the sinusoidal are from the scope probe sensitivity to e-field noise. The scope probe has the center clip -on  removed, and the  plastic barrel removed along with the ground clip ( 3" ) . . The center conductor is  is now connected to  C54, or C55 or C56 ceramic  Vout bus . The metal barrel is has a short bare wire wrapped around it( 1CM long) and it is connected across the same ceramic .  This the preferred  method for measuring ripple