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BQ51013B: Output current glitch

Fonia
Prodigy 20 points
Part Number: BQ51013B
Other Parts Discussed in Thread: BQ24072T

Hi,

I'm including the BQ51013B and BQ24072T  to charge single LI-ION battery. RX coil is TDK WR303050-15F5-G  (Ls = 12uH, Rdc =390mohm)

When using connect BQ24072T directly from a DC source for battery charging ( charing current 300mA), BQ24072T works well with normal input/outpu current waveform.

When using BQ51013B, the output current of BQ51013B has glitches.

Vrect is aournd  5.7V.  Battery charge current sees no problem.

I've looked in to the SCH checklist and other 3 related docs but still can't fix it.

All the parametes on the PCB are same as described in BQ51013B datasheet.

 

Thanks，

Follin

  • 0
    TI__Guru 67476 points

    Hi Follin

    The glitch seen on BQ51013B OUT is probably communications packets, they appear to be at a 250ms rate.  Also check the RECT voltage, this voltage supplies OUT regulator.

    Couple of things to try.

    1.) Increase OUT capacitors

    2.) Increase RECT capacitors

    4.) Re-Tune the Series and Parallel Resonant Capacitors, Data sheet section 9.2.1.2.2.  

    5.) Adjusting COMM1 / COMM2 capacitors slightly higher or lower may help.  But too much of a change will cause communication problems.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Hi Bill,

    I've looked into the datasheet again, and it says when I < 40% Imax it will always send error packets to converge. Currently I'm using Io = 300mA and Imax should be set at 1.2A, will it affect? 

    And I've made two layouts with same circuit (same componnet parameters). The glitch on the other one seems much smaller than this one. 

    I'll try your suggestions, thanks！