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Original question:

TPS50601-SP: Synchronization Timeout

TPS50601-SP: Synchronization Timeout

Jerry Molisani
Prodigy 80 points
Part Number: TPS50601-SP

The last response in this thread stated that, after an external sync signal is applied, if it is later removed, the TPS50601-SP will not switch back to using the internally-generated sync signal.  If that is true, then what does it do?  Does it just stop functioning?

Another question:  the datasheet states that "When operating the converter in internal oscillator mode ..., the synchronous pin becomes the output".  This contradicts Table 1 in the datasheet.  Elsewhere in the datasheet it states that the sync pin is an output only in master mode, which is when the RT pin is left unconnected.  So my question is this:  is the sync pin ever an output when there is a resistor connected from the RT pin to AGND?  I'm concerned that there could be contention between the externally-supplied sync signal and the internally-generated sync signal both trying to drive the sync pin simultaneously especially at the point when operation switches from the internal sync signal to the external sync signal.

Thanks,

Jerry Molisani

  • 0
    TI__Expert 4420 points
    Hi Jerry, perhaps I wasn't clear enough before, I apologize for the confusion. Eventually yes, the device will start running at the frequency set by the RT resistor (or the internal oscillator frequency if the pin is floating) but it will take typically at least 25us before that happens.
    Regarding your second question, the only situation in which the SYNC pin becomes an output is when the RT pin is floating. In this case, it will output the internal oscillator frequency (500kHz), 180 deg out of phase. The reason why we mention master mode is because typically, you would want to avoid using an external clock in master/slave configuration and therefore you would leave the RT pin of the master device floating and connect the SYNC pins of the master and slave devices. The RT pin of the slave device needs to have a resistor to AGND representative of the 500kHz clock.

    Please let me know whether this response answers your questions.

    Thanks,

    JV
  • 0 in reply to Javier Valle
    Prodigy 80 points

    Hi Javier,

    Yes, your response answers my questions.

    Thanks,

    Jerry