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BQ51222: Typical RFOD and question about "compromises to meet WPC and PMA"

Alexander Sevcik
Prodigy 20 points
Part Number: BQ51222
Other Parts Discussed in Thread: BQ51003, BQ51020, BQ25170, BQ51221, TIDA-00243

Hello,

I read the user manual about dimensioning RFOD and understand, that this has to be checked on the final product with a calibrated transmitter and the necessary tools.

But with what default value should I start?

I downloaded the "FOD Calibration" Tool to find out the default value, but the BQ51222 is not listed there.

I choosed BQ51222 because of the low price (compared to the others) and the high stock of this product.

I read many threads about the BQ51222 because it seems like TI is not recommending it if only one standard is used.

One example: BQ51222: About BQ51222 and BQ51052B : wireless charging solution - Power management forum - Power management - TI E2E support forums 

<<<

" .. The BQ51222 makes a number of compromises to meet WPC and PMA. "

>>>

What are those compromises?

I plan to wireless charge a small battery (140mAh), with a receiver current of max 280mA (140mA for the product and 140mA max. for charging).

BR, Alexander Sevcik

  • 0
    TI__Guru* 75656 points

    Hi Alexander

    The battery charge current is low and this will give your a number of options for charging devices, BQ5105XB, BQ51020 or 21, BQ51003 + BQ25170 and others.

    Any possibility of using other devices?

  • 0 in reply to Bill Johns
    Prodigy 20 points

    We already have an IC which charges the battery and provides all necessary board voltages, sorry for the misunderstanding.

    We need to provide 5V which needs to deliever  ~200mA.

    The main question was:

    1) default value for BQ51222 FOD-resistor?

    2) Which compromises where met with the BQ51222, why is the first answer to BQ51222 related question always a suggestion of alternative components?

    I can use an alternative IC, as long as it has the same (or lower) price and the same (or better) availability.

    If I saw it correctly the BQ51020 is pin compatible to the BQ51222, only thing which has to be considered is an additional resistor from VIREG(222)/VTSB(020) to TS/CTRL.

  • 0 in reply to Alexander Sevcik
    Prodigy 20 points

    Now I read all remaining E2E forums related to this IC.

    I now understand that BQ51222 is equal to BQ51221 (only communicates that it is a v1.2 receiver), so I can use the standard FOD-resistor mentioned for BQ51221.

    But the second question is still open. 

    What are the downsides when using the dual receiver BQ51222? Are they really relevant for my solution?

  • 0 in reply to Alexander Sevcik
    TI__Guru* 75656 points

    The difference between the BQ51221 and BQ51222 is data in ID packet, WPC 1.1 vs 1.2.  All info available for the 221 will apply to 222.  

    BQ51222 / BQ51221 WPC FOD EVM values can be reused.

    BQ51221 EVM User's Guide:

    https://www.ti.com/lit/pdf/sluuax6

    TI Reference Design TIDA-00243:

    https://www.ti.com/tool/TIDA-00243

    Application Note, Layout:

    https://www.ti.com/lit/pdf/slua710