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TPS53667EVM-769: Internal gain in TPS53667 COT controller

Sundaramoorthy Sridhar
Prodigy 15 points
Part Number: TPS53667EVM-769
Other Parts Discussed in Thread: TPS53667

Hi,

I would like to know if there is any internal gain in the isum feedback to PWM comparator in TPS53667 COT controller? The datasheet (for D-CAP+ control) expression (shown in Fig. 3) says that there is an gain of about 1/6 but the datasheet of TPS53667 (shown in Fig. 2) says the internal gain is 1. Also, there is no internal gain for VISUM_AC mentioned in the block diagram ( shown in Fig.1.) from datasheet of D-CAP+ control. 

Fig.1. Block Diagram of COT Controller

Fig. 2. Internal sense gain from datasheet of TPS53667

Fig. 3. Visum_ac Expression given in datasheet of D-CAP+ control

  • +1
    TI__Expert 5281 points

    Hi Sundaramoorthy, 

    The internal gain is 1/phase#, so it depends on how many phases are being used. If the phase is not being used, then the resistor is opened on the respective phase. If all 6 phases are being used, then it will be 1/6. The internal current sense gain Gscint measuring 1 is when one phase is used. 

    Best,

    Ryan

  • 0
    Prodigy 15 points

    Thanks for the clarification.

    I could see external ramp amplitudes ranging from 20mV to 200mV peak-to-peak in the fusion designer.

    I would also like to know if the peak-to-peak value of ramp that appears at PWM comparator (Vramp), shown in the block diagram, equals to the ones given in fusion designer or do we have any internal scaling factor for the ramp amplitude that appears at PWM comparator as well?

  • 0 in reply to Sundaramoorthy Sridhar
    TI__Expert 5281 points

    Hi Sundaramoorthy,

    The peak-to-peak values of Vramp are the same as the ones that appear in fusion designer. 

    Best,

    Ryan