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TPL5100 MOS_DRIVE 'ON' Period

David Gerber
Intellectual 315 points
Other Parts Discussed in Thread: TPL5100

Hello,

I just bought the evaluation board for the TPL5100 because I was thinking of incorporating it into my circuit for better power saving.

I've been playing with the EVM for quite some time and read the datasheets of the EVM and the TPL5100 a million times but I still can't get something straight...

According to the TPL5100 datasheet It seems that the MOS_DRIVE signal is LOW (i.e. turning ON the P MOSFET shown on the first page of the datasheet) for only two internal oscillation periods (as mentioned in page 8 second paragraph) if no DONE signal is received. This means that if I want to execute some code on the micro controller that was just now turned on then I have less than two internal oscillation periods to do so because then the MOS_DRIVE signal goes back up and turns OFF the P MOSFET. This doesn't make sense because this is less than 0.5 seconds and my micro-controller doesn't even have time to boot up before it gets shut down again. Am I missing something? Is there some way to keep the MOS_DRIVE signal LOW until I send a DONE signal from the micro controller? I thought that the datasheet perhaps is mistaken so I just tried to connect it to my circuit and see what happens but it indeed operates this way which makes no sense to me. 

I am completely baffled. 

Either I didn't understand how to use the TPL5100 or I didn't understand its intended use.

I would greatly appreciate your help. 

Thanks,
Eyal

  • 0
    Prodigy 10 points
    Hi,

    You're not the only one - I also cannot understand this behavior. the manual was even revised in December 2014 , and still it writes
    [quote]
    The frame, C, shows a standard sequence, but in this case, the TPL5100 receives the DONE signal when
    MOS_DRV is high and TCAL pulse is still high. As soon as the TPL5100 recognizes the DONE signal, the
    counter resets and MOS_DRV and TCAL return to default conditions (MOS_DRV signal high and TCAL signal
    low).The external power-gating MOS stays ON for the execution time of the program of the connected
    microcontroller.
    [end-quote]
    a. If the MOS_DRV signal is high, a connected mc is very much turned off, so how on earth could a DONE be recognised as it can never be send??
    b. The last sentence, wich initially triggered me to buy this timer, indicates a variable pulse, but is is practically impossible??

    Please TI / anyone, help

    Thanx,

    \Hans

    P.S. I solved this temporary by hooking up a lmc555im timer - the DRV signal triggers this timer.... by selecting the right R / C (monostable) the mc is power just long enough. It actually works but this was really not what I looked for...
  • 0 in reply to Hans Stapelberg
    Prodigy 20 points
    I want to wake up my µC with the TPL5100 every 512 Seconds.
    For this i like to connect only the MOS_DRV pin to the Interrupt Pin on the µC (i have only one pin left).
    So i can't send a DONE to the TPL5100.

    Is this possible?
  • 0 in reply to Stefan Schreiter69
    TI__Genius 9655 points

    Hi Stefan,

    you can connect only the MOS_DRV, in this case the uC will be automatically turned off when the ON time elapses.

    Please be sure to connect the PGOOD to VDD.

    regards,

    Domenico