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TPS566238: What is behavior on large Cout?

Motoyasu Hattori
Expert 8675 points
Part Number: TPS566238

Hi,

According to the Table 8-2 of TPS566238 datasheet, Cout MAX is 220uF.  However, my customer wants to use it on the following conditions.

  • Device : TPS566238 @ 600kHz SW-Freq
  • Inductor : 1.0uH
  • Input Voltage : 5V

  • Case1 : Output Voltage / Current : 1,0V @ 2.5A,   Cout ; 541uF
  • Case2 : Output Voltage / Current : 0.7V @ 4.74A,   Cout ; 444uF

Unfortunately, on all cases, Cout are >220uF.  On these cases, does they have any issues?  Please advise us.

Thanks and best regards,
M.HATTORI.

  • 0
    TI__Expert 3245 points

    Hi Motoyasu,

    This device uses DCAP-3 technology.  In D-CAP3, the regulator reacts within one cycle to the change in duty cycle so the good transient performance can be achieved without needing large amounts of output capacitance. Adding the extra capacitance will just increase the cost since the same performance can be observed with just 220uF.

    However, there could be negative effects of too much output capacitance. The impedance of the output capacitance affects the damping of the output filter and has a major affect on the transient response of the supply. It can also affect stability of the feedback loop. 

    I recommend to stick to what TI suggests in the datasheet with 220uF. You can also use the WEBENCH/SIMPLIS simulation to add the extra capacitance and see how that can affect the performance of the circuit. I also suggest for the customer to use our EVM if they would like to double check how the IC will behave with the extra capacitance.

    Regards,

    Akshat