BQ25700A: charge current oscillated issues

Jelly li

Intellectual 290 points

Part Number: BQ25700A
Other Parts Discussed in Thread: BQ25700

About BQ25700 charge current issues:

VIN=12V; set charge voltage 13200mV, REGN=5.99V; cell_batpresz=3.48V, 58%-3cells;

issue1: when VBAT<7.2V start charge, charge current oscillated;

issue2: in CV mode, charge current oscillated, much bigger than you test on DB 30mmA ripple, how to decreas?

issue3: the same with light load, CV mode charge switch to OTG mode, the current ripple is big different, how to explain？

0x12[10]=1, set minimum PFM burst frequency to above 25kHz to avoid audio noise, will be valid for charge and OTG mode?

look forward you Answer ASAP.

Thanks

JellyBQ25700 current.docx

over 5 years ago

0 Paul Yeh over 5 years ago

TI__Genius 13625 points

Jelly,
Can you send schematic for reference?
Did you use real battery for evaluation?
Thanks

0 Jelly li over 5 years ago in reply to Paul Yeh

Intellectual 290 points

6735.BQ25700 current.docxHi Paul，

actually , we set charge voltage 13.2V. no load on system side; when VBUS power off, need VCAP supply the input side.

charge current issue and related SCH attached , plese give you advice.

Thanks

0 Paul Yeh over 5 years ago in reply to Jelly li

TI__Genius 13625 points

Jelly,

From your schematic, it seems you didn't use BATDRV signal to control BATFET. Why you not use it?

So far my suggestion for your oscillation symptom is to add 6pcs 10uF or equivalent capacitance in Q4 drain and VSYS(pin22) side for buck-boost output bulk cap purpose.

Thanks

0 Jelly li over 5 years ago in reply to Paul Yeh

Intellectual 290 points

hi paul, thanks for your reply.
i send the old version sch, actually we have design as your typical application, there is 6*10uF capacitor at the VSYS side, in CV mode , the current is oscillated . we add more 6*10uF capacitors, there is no difference. would you give me other suggestions? thanks

0 Paul Yeh over 5 years ago in reply to Jelly li

TI__Genius 13625 points

Jelly,
Can you try to change R22 & R23 value from 10ohm to 4.99ohm?
And please also check this oscillation is switch frequency or not, maybe it is PFM mode ripple current or voltage, not oscillation.
Thanks

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BQ25700A: charge current oscillated issues