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TPS548D22: ripple injection

K.Hamamoto
Guru 12155 points
Part Number: TPS548D22

Hi

I have some question about the ripple injection for this device.

I think  the following circuit(R5,C31,C36) are DNP is the ripple injection circuit. Is that correct?

If it so,

1. How can we calculate the value of the circuit?

    (The condition is Vin=12V, Vo=1V, Io=450kHz, L=0.2uH.)

2. Is there any limitation?

3. Also could you advice me if there is any concerns to add the circuit?

Best Regards,

Koji Hamamoto

  • 0
    TI__Guru**** 191445 points

    Hamamoto-san,

    TPS548D22 uses DCAP3 control mode.  DCAP3 has internal ripple injection so those components are not needed.  TPS548D22 has the capability to revert to ordinary DCAP mode, which may require external ripple injection, depending on the ESR of the output capacitors.  This mode is intended for advanced users who are familiar with ripple injection.  The ripple injection in this case should be between 10 and 15 mV.  If you intend to operate in DCAP3 mode, you do not need to be concerned with external ripple injection.  If you are planning to use ordinary DCAP, can you tell me about your application and why you intend to operate in this mode?

  • 0 in reply to JohnTucker
    Guru 12155 points
    Hi John-san,

    I apologize for this late reply. I have talked with the customer. They would like to improve the transient performance.
    Of course, the compensation should be tuned but it will need faster transient.
    That is why they would like to know how can they put the ripple injection circuit.
    If there is other way to improve the transients performance,please advice us.

    Best Regards,
    Koji Hamamoto