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TPS53319: About ripple injection circuit

Part Number: TPS53319

Hi,

When designing without a ripple injection circuit, what merit or disadvantage can be considered?
If it is required, why is it necessary?
My customers are confirming normal operation by removing the ripple injection circuit against the phenomenon that the load response can not follow and the UVP or OVP of the FB pin is applied and the device stops. Therefore, I would like to present the merits, demerits and reasons (if necessary) to the customer, which can be thought out by removing the ripple injection circuit at TPS53319.

<condition>
Vin=19V,Vout=5V,Iout=10A,injection voltage level=30~40mV

Best Regards,
Yuto Sakai

  • Sakai-san,

    TPS53319 uses DCAP mode control. DCAP is a n adaptive constant on time, semi hysteretic off time control. The analog on time controller stets the on time for each cycle proportional to Vout / Vin. The off time is terminated by a hysteretic comparator when the FB pin voltage falls below the internal reference voltage. For this hysteretic off time controller o work properly, there must be a sufficient ripple voltage component at the FB pin. This can generally be accomplished two ways. If using electrolytic output capacitors with some significant ESR, then the ac inductor ripple current times the output capacitor ESR will generate a sufficient ripple component. If using low ESR or ceramic output capacitors, you can use the ripple injection circuit to inject ripple at the FB pin. Insufficient ripple voltage can cause very large amounts of jitter in the switching waveform.

    Does this answer your question? We most likely have training materials on this that can be shared. You can contact me off line, I'm sure you know my contact info ;-)

    Let me know how we can help you further.
  • Hi John-san,

    Thank you for your reply.
    I mailed you offline.
    Also, I have additional questions.
    Is it acceptable to use electrolytic output capacitors with some significant ESR with a small-capacity ceramic capacitor for high frequency noise countermeasure and mix?
    In that case will ripple injection circuit be unnecessary?

    Best Regards,
    Yuto Sakai
  • I'll forward the file to you tomorrow