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BQ51013B: Reduce t_hold timeout of 1s

Marco Dori
Prodigy 65 points
Part Number: BQ51013B
Other Parts Discussed in Thread: BQ51050B, TPS61500

Hi, i'm currently developing a pcb with the BQ51013B IC as energy source but we have encountered a problem with the delay of one seconds before the Vout is enabled by the device.

There are any solution to disable this delay or to reduce it?

The only one IC that doesn't have the delay is BQ51050B but without battery it doesn't work when the power surpass 1W.

ps. The pcb is composed by the wireless charger circuit and a light driver circuit (TPS61500).


Thanks a lot,

Marco

  • 0
    TI__Guru* 75486 points
    Hello
    Check the voltage at RECT pin.
    Time between RX place on TX and Vout enable could be due to time it takes to tune the TX to 7V at RECT pin, then Vout is enabled. If this is the problem area then adjusting the coil tuning could be a solution.
    Other thing could be poor communication at start up where it takes a couple of tries before RX to TX comm is set up. Increasing value of communications caps may help this.
  • 0 in reply to Bill Johns
    Prodigy 65 points
    Dear Bill,

    I've checked the RECT pin and, as you said, it takes one seconds to tune TX to 7V. I've tried to increase the caps at COMM pins but i've earned only 20 ms at maxiumum.

    There are other solutions to "lie" to the IC or speed up more (we would like to decrease the output delay of 500 ms or more).

    Thanks a lot for the collaboration,
    Marco
  • 0 in reply to Marco Dori
    TI__Guru* 75486 points
    Hi Marco
    Also need to check the TX, time between pings they are often 500mS. The TX will check for an RX by powering the coil and look for a reply from RX. This is typically done every 500mS.
    Which TX are you using?
  • 0 in reply to Bill Johns
    TI__Guru* 75486 points
    Hi Marco
    I've checked the RECT pin and, as you said, it takes one seconds to tune TX to 7V. --- Bill J -- Check the tuning on RX coil, see section 8.2.1.2.2 of data sheet, Series and Parallel Resonant Cap
  • 0 in reply to Bill Johns
    Prodigy 65 points

    Dear Bill,

    We already performed the calculations for Cs and Cd caps and we changed the caps from 10nF to 22 nF and 47 nF connected to COMM pins but it hasn't improved.

    Only decreasing the distance between coils has reduced the delay, currently the distance is 5 to 6 mm, decreasing it to 3 mm has reduced the delay from 1600 ms to 800 ms (but we can't reduce the distance this much).

    For TX power transmission we are using Silvertel AG320T with the coil 760308103102 (Wurth), on the Rx we are using the coil 760308102207 (Wurth).

  • 0 in reply to Marco Dori
    TI__Guru* 75486 points
    I will contact you with forum Private Message.