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POLA (e.g. PTH08T250W) Track and Inhibit Control

Xuezhuan
Prodigy 100 points
Other Parts Discussed in Thread: PTH08T250W

Hi,

We know we can use Inhibit Pin to enable/disable POLA output. I want to know if we can also use Track pin to turn on/off the module:

1. Pull Inhibit Pin Low(Use NMOS) => disable output;

2. Inhibit Pin is open, pull Track Pin low then disable output;

3. Inhibit Pin is open, pull Track Pin High (e.g, 12V), then enable output;

Thanks.

  • 0
    TI__Mastermind 38230 points

    Xuezhuan:

    The track pin when grounded through a FET  or by an external bus to ground will disable the  power module. The data sheet page 24 has addtiopnal data.

     Extract from PTH08T250W autotrack control function

    Notes on Use of Auto-Track™

    1. The Track pin voltage must be allowed to rise above the module set-point voltage before the module regulates at its adjusted set-point voltage.

    2. The Auto-Track function tracks almost any voltage ramp during power up, and is compatible with ramp speeds of up to 1 V/ms.

    3. The absolute maximum voltage that may be applied to the Track pin is the input voltage VI.

    4. The module cannot follow a voltage at its track control input until it has completed its soft-start initialization.

    This takes about 20 ms from the time that a valid voltage has been applied to its input. During this period, it is recommended that the Track  pin be held at ground potential.

    5. The Auto-Track function is disabled by connecting the Track pin to the input voltage (VI).  When Auto-Track is disabled, the output voltage rises according to its softstart rate after input power has been applied.

    6. The Auto-Track pin should never be used to regulate the module's output voltage for long-term, steady-state operation.

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 100 points

    Thank you, Tom.

    I see datasheet mention we can use open-drain to control Track pin, so Track pin can be floating? but why "If unused, this input should be connected to Vi" at data sheet page 6?

    I'll use this method to implement Track control, if it is OK? and don't need add any pull up for Track Pin? Thanks.

  • 0 in reply to Xuezhuan
    TI__Mastermind 38230 points

    Xuezhuan:

    The track pin  has its own internal pull-up to 5V. In order to defeat the  track pin when not used, it should be connected directly to input voltage.

    The FET open drain circuit is one method to control the track pin. One requirement for track control  is the FET gate voltage should be delayed by minimum 20msec after 12V is applied to the input power pins.

    tom