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UCC28063 Switching of the single-phase mode and the 2-phase mode

Kuramochi Tadahiko
Guru 28715 points
Other Parts Discussed in Thread: UCC28063

Hi,

My customer is evaluating the UCC28063.

The PHB pin is tied with the COMP pin on their circuit.

When ON/OFF of the Bch output is switched by PHB pin, Vout becomes unstable.

The unstable condition is that  the GDB pin sometimes outputs the voltage, it doesn't sometimes.

At the unstable condition the load current increases, and the Vout becomes stable.

They expects that this condition is caused by the large variation of the voltage of the PHB/COMP pin.   

Could you please show me how to improve this unstable condition by the circuit constant?

I guess that increasing the Cp improves this condition, is it wrong?

Thanks and Regards,

Kuramochi / JPN Disty 

  • 0
    TI__Mastermind 34465 points
    Because the value of the COMP signal is used as a parameter here, this method of phase management may result in a system instability if the voltage loop compensation components are incorrectly chosen.
    Please use the calculator tool for the UCC28063 and test for system stability with the phase management option disabled. Alternatively monitor the output current and use external thresholds of current to decide between single or dual phase operation. Since the output voltage is fixed, you can use the measured current as a proxy for power output.
    Regards,
    John Griffin