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Maybe some errors in schematics

Other Parts Discussed in Thread: TIDA-00762, TIDA-00623, BQ50002, BQ500511

Hello,

I come again for your help.

After some research, I decided to use tida-00623(5W) or tida-00762(1W).

tida-00762 use a 6.5 uH coil and I found that this coil should fit :

tida762 is rated for 1W but its coil is rated for 3A?.

tida623 use a 6.3 uH coil.

So I compared schematics of tida762 and tida623 and found only some few differences and strange things.

- tida623 use 22 uF caps for pvin1 and 2                                 tida762 use 10 uF caps instead                          bq50002 documentation says it has to be 22 uF.

- tida623 shows pin 4 ilim with resistor                                    tida762 has resistors and 3.3V                           bq500511 documentation says it's a reserved pin

- tida762 use some kind of filters before the coil                   

- tida623 use flim pin

Could you tell me if those differences are the reason of power abilities? and what I missed for the pin 4?

I think it's very close of what I want to do (2.5W and the previous coil).

thank you for your help

  • Hello
    TX coils for TIDA-00762 --- The Wurth 30mm coil (760308101103) is shown on the design. The Wurth 20mm coil (760308101104) can also be used. Both are 6.3uH coil +/- 10%. The 5W coil is also a 6.3uH coil +/- 10%. If the coil inductance is in this range it will work.
    The DC resistance of the coil should be kept low for good thermal performance. This low DCR requirement will drive the coil current rating.

    ---PVIN 1 / 2 bulk filter capacitors reduced on the 1W application, less filtering is required for the lower power application.

    ---bq500511 Pin 4 --- Unused in the final version of the device and can be left open.

    ---TIDA762 use some kind of filters before the coil --Could this be TIDA623? It will used C10/R8 and C18/R16 as snubbers to reduce noise and voltage spikes in the 5W application. Lower power applications do not require them.

    ---TIDA623 use FLIM (Pin 33) --- The pin should be left open, TIDA-00762 does not need the option to connect a pull down resistor.

    ---For operation at 2.5W check the thermal rise of bq50002 and resonant capacitors C1, 2, 3 and 4. Also look for voltage spikes at SW1 & SW2 node. The PCB was made small to reduce solution size this will reduce copper used to cool the TX.
  • Hello,

    thank you for your answer, it's more clear now.

    If I well understood:
    - my coil is ok for this application.
    - for 2.5W, I have to filter pvin 1/2 between 10uF and 22uF (is there a way to calculate it?)
    - I don't need to filter before the coil
    - pin 4 and 33 are left floating
    - C1,2,3 and 4 (resonant tank?) have to be at 100nf C0G
    - for thermal issue, if I make wider tracks, is it more safe?

    thank you a lot,
  • Hello Frederic

    Reply to your questions below:
    - my coil is ok for this application---yes, 20mm Wurth coil will work (TDK also makes a 20mm coil)

    - for 2.5W, I have to filter pvin 1/2 between 10uF and 22uF (is there a way to calculate it?)---If you have the room to work with use 22uF or greater. Check the ripple voltage on the bus at full load.

    - I don't need to filter before the coil---The snubber is for EMI and voltage spikes. Again if you have the room add it to the layout and make a decision later to populate the ckt.

    - pin 4 and 33 are left floating--yes

    - C1,2,3 and 4 (resonant tank?) have to be at 100nf C0G---yes

    - for thermal issue, if I make wider tracks, is it more safe---yes but make the ground plane as large as you can to spread the heat out.
  • Hello Bill,


    Thank you for your answer.

    It's great, now I have all I need.

    thank you a lot, it's very kind.

    best regards,

    frederic