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Question about ramp generator of LM5020-1

Satoshi
Guru 19645 points

Please let me know about ramp generator(below) of LM5020-1.

---------------------------------------------------------------

・I think that datasheet P8 write below contents, is it right?

　⇒Slope ramp signal is compare with "（Error AMP output＋1.4V）×1/3" by a PWM comparator.

・Ramp signal is 0V to 105mV(typ).

　In the case of Duty:50%, ramp signal is between 52.5mV to 105mV, is it right?

・If above is right, I think the 52.5mV is too small to Error AMP output.

　Is it mistaken where my way of thinking?

---------------------------------------------------------------

Best regards,

Satoshi

  • 0
    TI__Guru 74002 points

    Hello Satoshi,

    (COMP - 1.4V) / 3 is one input to the LM5020-1's PWM comparator. The other input is the current sense signal plus the slope compensation signal, which at 50% duty cycle is an additional 52mV above the CS pin voltage (assuming no additional series resistance is added in series with the CS pin). You can reference this level back to COMP by multiplying by 3 and adding 1.4V.

    Regards,

    Tim