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Auto-track max slew rate on PTH08txxx family

Allan Herriman
Prodigy 140 points
Other Parts Discussed in Thread: PTH08T210W, PTH08T220W

Hi,

I'm using the auto-track inputs on PTH08T220W and PTH08T210W in a design for a client.

The datasheets for those parts specify a maximum slew rate "capability" on the auto-track inputs of 1V/ms.

 

My design has a small fet that can pull down the auto-track voltage rather quickly and I have a large (4mF) capacitance on the output of the PTH08T210W.  Will this cause any damage?  How can I predict the output voltage waveform under these conditions?

 

Thanks,

Allan

  • 0
    Prodigy 140 points

    Perhaps I should ask a different question since that one didn't get any response...

     

    The Auto-Track app note slyt095.pdf says "each Track pin is also provided with its own RC charge circuit that can produce a suitable rising voltage from the input source voltage."

     

    Could someone please post details of this circuit?  I know from reading the datasheet that the Thevenin equivalent of the track input is something like a 60-70kohm resistance pulling up to 8V or so, but I can't tell how the capacitor is connected.

  • 0 in reply to Allan Herriman
    TI__Mastermind 38230 points

    Hi Allen:

    The auto track function  dv/dt for PTH08T2 is different  of each group of PTH08T2 modules.

    The PTH08T210  is pulled up to 5V with  a 43.2k resistor The circuit has   a 1uf  capacitor and a 43.2K resistor. The RC is 43 ms to maximum 5V.

    The PTH08T220 through PTH08T260 is pilled up to 6.2V maximim with a  56k resistor. The circuit has   a 1uf  capacitor and a 56K resistor. The RC is 56ms to maximum 6.2V.