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TPS22995H-Q1: Control slew Rate with capacitor does not seem to function as expected

Andre Lochner
Prodigy 20 points
Part Number: TPS22995H-Q1
Other Parts Discussed in Thread: TPS22995,

Hi

I am building a circuit to manage the inrush current. I am trying to increase slew rate and reduce inrush current using the TPS22995.  From my understanding the capacitor on CT pin should determine my slew rate. What I see is counter to what I expect. If I add a capacitor on CT I get higher inrush current then if I leave it open. As I increase CT capacitance the measured inrush current increases. The slew rate of the Output voltage seems to stay fairly consistent. I measure the current using a shunt resistor of 1ohm between power supply andTPS22995. Any help would be appreciated ! 

My circuit looks the same as in the schematic, my load is a 47uF capacitor only and my power supply is 3V with current limit set to 2A

Screenshot showing inrush current with CT left unconnected, orange is on signal, purple is Vout connected to 47uF Capacitor to ground

Screenshot showing inrush current with CT connected with 0.1uF Capacitor to ground, orange is on signal, purple is Vout connected to 47uF Capacitor to ground

  • 0
    TI__Mastermind 24560 points

    Hi Andre,

    Welcome to e2e! I apologize for the delay, as it is currently a holiday season in the US and many support staff are out of the office.

    One thing I notice is that the question title refers to TPS22995H-Q1, while you show that you are using TPS22995. The two devices use a different slew rate control mechanism - TPS22995 uses a capacitor while TPS22995H-Q1 uses a resistor. If you are using TPS22995H-Q1 with a capacitor, that would explain the behavior you are seeing. Which device are you using?

    Thanks,

    Patrick