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[BQ51050B] RFOD value

Chang-woo YANG
Expert 1285 points
Other Parts Discussed in Thread: BQ51050B, BQ51050BEVM-764

Hello~

According to page 9 on the BQ51050B datasheet, RFOD value is 188ohm.

But, in the page 20 of BQ51050BEVM-764 user's guide, R2 (RFOD) value is 200ohm.

What is correct value???

Please clarify.

Thanks... C.W. :)

  • 0
    TI__Mastermind 32350 points

    C.W,

    If you want to be compliant with WPC1.1, The R_FOD value needs to be calibrated. If wpc1.1 is not a requirement, a 188 should do it. And you will need to re-calculate the RILIM accordingly.

     Thanks!

    Tahar   

  • 0 in reply to Tahar Allag
    TI__Mastermind 45250 points

    Tahar,

    Can you go into more detail regarding this (calculations etc.)? My customer questions as as follows:

    How exactly is the FOD resistor calibrated? I would like to comply with WPC 1.1. I am running into the same issues that I've seen from others on the TI Wireless Power forum. A higher bulk current is leading to the charger cycling on and off, whereas a much lower one allows the charger to remain on. I currently have the R_FOD resistor set to 200 ohms as shown in the bq51050EVM schematic, but I am experiencing the charger cycling on and off when placed on a transmitter, when attempting to charge at I_bulk (600mA in this case). It would be great if you could lend some guidance on how exactly to calibrate the FOD resistor. Is there a calculation? I am familiar with the "P_received - 250mW <= P_PR <= P_received" relationship, but I don't know how to correspond that with the FOD resistor. Is that power being reported on the FOD input of the IC? Does the Ros resistor (currently set to 42.2kohm) need to be adjusted as well?

    What calculations must the customer do to be compliant?

    Thanks for your help with this!

    Richard Elmquist