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UCC28950: Adding a capacitor during EA- and GND

Kuramochi Tadahiko
Guru 28715 points
Part Number: UCC28950

Hi,

My customer is considering adding a capacitor(100pF~1000pF) during EA- pin and GND.

Does it allow for stability?

Best Regards,

Kuramochi

  • 0
    TI__Mastermind 25570 points

    Hello Kuramochi-san

    It depends - the customer should calculate the resulting pole in the transfer function - normally the capacitor along with the resistor to ground. On our EVM (sluu421a) the resistor is 2.37k and 330pF would give a pole at 200kHz. This is high enough that it won't affect the closed loop response at all so the added capacitor would be ok.

    I would expect that if the pole is 10 times or greater than the closed loop bandwidth there would be no problem. It is also very important to keep the PCB track from the EA- pin to the potential divider as short as possible - this is to reduce the level of electrical noise picked up by this high impedance node. A reduced level of noise pickup will allow the use of a smaller value capacitor.

    Regards
    Colin