• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 684 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ51050B: bq51050B, No comm seen on Rect

Mark Haskins
Prodigy 35 points
Part Number: BQ51050B

I have been trying to get our PCB working, based on the bq51050B chip and the standard/eval diagrams. wireless charging only, with a 1250mA lipo plugged in. The Rect waveform shows the Tx ping but there is no comm presant.

Similar to the thread http://e2e.ti.com/support/legacy_forums/wireless_power/f/693/t/619980

I have checked for any shorts ect and cannot find anything, I note that the voltage at the junction of R1 Rfod & Ros is basically 0V should this be so? I have tied TS/CTRL with a 10K to GND, AD to GND, coil is Wurth 760308101303

Rect

Comm1

Comm2

Schematic

  • 0
    TI__Guru* 75656 points
    Hello Mark
    The RECT voltage is very high, looks like 12 to 14V --- is this right?
    What is the coil to coil distance?

    Wurth Coil 760308101303 has a high L, 47uH so the tuning needs to be adjusted from 47nF / 68nF / 68nF to about 50nF total. 47nF should work for test.

    AD -- Grounded, good
    TS/CNTR -- To gnd with 10k good
  • 0 in reply to Bill Johns
    TI__Guru* 75656 points

    See attached start up.

    The output will turn on last.

    Once communications start the RX will tune TX operating point to RECT target voltage.  This will take several packets.  At that point the output is turned on.

    6646.bqTESLA FAQ--Start up.pdf

  • 0 in reply to Bill Johns
    Prodigy 35 points

    Hi Bill,

    Thank you for your help, I changed the C1 cap to 47nF and one of the two boards I have been testing started to comm, it starts a charge but drops out after about 3 seconds on one of the chargers (Semtech TSDMTX-19V3-EVM) with 10mm or 6mm spacers between coils. The other charger (Caseflex Qi Wireless Charger) holds transfer at the 1A as required with a 4mm spacer, you are right the Rect does seem high compared to supplied PDF, not sure why. So its working but does not seem particularly robust, any suggestions would be appreciated.

    10mm spacer (Semtech TSDMTX-19V3-EVM)  yellow=Rect & blue=AC2

    6mm spacer (Semtech TSDMTX-19V3-EVM) yellow=Rect & blue=AC2

    4mm spacer (Caseflex Qi Wireless Charger) yellow=Rect & blue=AC2

    close up of waveform

    4mm spacer (Caseflex Qi Wireless Charger) yellow=Rect & blue=AC2

    Bench