LTC2955-1 Push Button Press Duration

I want to implement the LTC2955-1 in our company project and would like to know the following.

1. Am I correct to assume that if the Vin(wall-adapter) is connected to the ON pin of the LTC2955-1, then it automatically drives the output after a 32ms delay?

2. I want to make sure that when the wall-adapter power is not present, the device is turned on ONLY AFTER the PUSH-BUTTON is pressed for a duration of 900ms. I know that the delay can be adjusted by varying the capacitor value on the TMR pin? My calculation gave me a capacitor value of 173nF to get a delay of 900ms.

  • 1. Am I correct to assume that if the Vin(wall-adapter) is connected to the ON pin of the LTC2955-1, then it automatically drives the output after a 32ms delay?

    Yes, that is correct.

    I am assuming the ON pin is monitoring the wall adapter while the LTC2955 has a separate supply for its Vin pin.

    Let me know if this isn’t the case.

    2. I want to make sure that when the wall-adapter power is not present, the device is turned on ONLY AFTER the PUSH-BUTTON is pressed for a duration of 900ms. I know that the delay can be adjusted by varying the capacitor value on the TMR pin? My calculation gave me a capacitor value of 173nF to get a delay of 900ms.

    The timer pin determines how long PB# must be held low to release EN, not to turn it on.

    If you want to debounce PB# for turn on, you need an ONT pin.

    Check out the LTC2950 or LTC2954.

    Hope this helps,
    -Aaron

  • If you want to debounce PB# for turn on, you need an ONT pin.

    Check out the LTC2950 or LTC2954.

    If I use the above two parts, I loose the auto power on functionality when wall adapter power is plugged in. right? Any way I can implement the on time delay as well as auto power on feature at the same time?

  • The LTC2955 is the only PB controller with automatic turn-on, but its debounce time for turn-on is fixed at 32ms. The LTC2950/4 has adjustable debounce time for turn-on, but doesn’t have automatic turn-on. Unfortunately, you cannot mix and match these features.