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TPS2492 timer

Other Parts Discussed in Thread: TPS2492

Hi,

I'm using the TPS2492 and I want the TPS2492 will turn off exactly at the time it sensing the over current.

What is the minimum capacitor value I can assamble to get the fastet response?

Shmuel

  • Shmuel,

    You can utilize the fast trip response of TPS2492 which only requires that the VCC-SENSE be overdriven by 4x of the current sense trip voltage (50mV). The conditions for this event are shown in the EC table as tF_TRIP and the response time is 1.2us.

    You can also refer to the tD_FAULT which is also 1us maximum.

    The TIMER pin could theoretically be left open in an environment without noise. A minimum of 50-100pF is recommended if the TIMER function was not used. We have some applications (http://www.ti.com/lit/an/slua500/slua500.pdf) where the Ct was 680pF and this yielded a delay of ~100us.

     

  • Eric,

    First, I didn't undestand the setup for 1.2uS.

    Second, I attached 2 pictures that shows the respons of IMON according to UV enable.

    Channel1- UV enable

    Channel 2- Timer

    Channel 3- IMON

    Channel 4- VOUT

    1 picture is without any load and the second is with 2A load whaiting.

    Can you please explane me the strange response of the IMON?

    Thanks

    Shmuel

  • Shmuel,

    The fast trip response time setup is as follows: Connect PROG to VREF (4V) and OUT to SENSE. Connect GATE to OUT with a 2nF capacitor. Quickly slew the voltage between VCC and SENSE from 0 to 200mV and GATE will slew low quicky within 1.2us maximum.

    Regarding the IMON waveform, this is the power limited current response waveform being controlled by the TPS2492. You can see this current reflected as the actual FET current during startup shown in Figure 13 and 14 of the datasheet.

  • Eric,

    The behavior of the IMON is very strange. I didn't understand why the IMON is jumping so high and then after 2mS from power on the IMON set the right current value.

    I'm using in design the IMON as input to a comperator with DAC and this behavior sets errors.

    Please explain again.

    Shmuel