topic Re: PCA9420 Battery detection in-progress ? in Power Management

PCA9420 Battery detection in-progress ?

akckwang — Fri, 30 Sep 2022 03:08:09 GMT

Hi,

Our device adopts PCA9420UKZ to be pmic,
and charging source is Qi wireless charging,

When we charging battery by Qi wlc charger,
if antennas aren't aligned very accurately,
even charger feels everhthing is right and keep power output,

the pca9420 would stop charging because it falled into a state "Battery detection in-progress",
(CHG_STATUS_2(1Ah) = 0x10, "Battery detection in-progress", "Charger in Idle State")

but at the sametime, register reveals pca9420 has detected battery,
(CHG_STATUS_0(18h) = 0xf0, "VBAT_DET_OK = 1", "VBAT_OK = 1")

Detailed register values:

0x01=0x00, 0x02=0x00, 0x03=0x3f, 0x04=0x00,
0x05=0x7f, 0x06=0x00, 0x07=0xff, 0x08=0xff,
0x09=0x41, 0x0a=0x81, 0x0b=0xce, 0x0c=0x01,
0x0d=0x00, 0x10=0xaf, 0x11=0x14, 0x12=0x02,
0x13=0x13, 0x14=0x0a, 0x15=0x25, 0x16=0x95,
0x17=0x24, 0x18=0xf0, 0x19=0xc0, 0x1a=0x10,
0x1b=0x00, 0x20=0x10, 0x21=0x00, 0x22=0x14,
0x23=0x2c, 0x24=0x41, 0x25=0x2c, 0x26=0x1c,
0x27=0x4c, 0x28=0x4f, 0x29=0x0c, 0x2a=0x1c,
0x2b=0x4c, 0x2c=0x4f, 0x2d=0x0c, 0x2e=0x1c,
0x2f=0x4c, 0x30=0x4f, 0x31=0x0c

datasheet of pca9420 mentioned the battery detection sqquence at "Figure 10. Charger state diagram",
but we still have no idea how pca9420 to have suceh state,
because seems the voltage we measured doesn't match the conditions of document description,

So we do like to consult more detailed of the "Battery detection in-progress",
How it happened?
Do we have way to know the truly VBAT voltage what pca9420 detected?
Any suggestion to investigate more forward?

2022-09-30:
Try to measure VBAT voltage by oscilloscope,
the voltage has ~0.1V gap between 2 case,
but when wlc charger isn't aligned perfectly, the frquency is ~37Hz only,
compare to aligned perfectly case, the frequency is very low,
is't caused pca9420 can't detect battery?

Thanks~

Re: PCA9420 Battery detection in-progress ?

guoweisun — Mon, 26 Sep 2022 06:33:13 GMT

The device has a unique battery detection scheme with two comparators, 1.9V and 3.4V.
when the detection scheme is executed, a 5mA current sink is activated to determine
battery presence by detection the fall threshold, VBAT_DET_LOW, 1.9V typ. In addition,
a 5mA current source is used to detect battery voltage whether it stays above the
threshold, VBAT_DET_UP, 3.4V. if both conditions are met, absence of battery is declared.

Re: PCA9420 Battery detection in-progress ?

akckwang — Mon, 26 Sep 2022 09:09:49 GMT

Hi Guoweisun,
Your reply is exactly what pca9420 document Figured 10 mentioned,
and that can't explain why our pca9420 can't detect battery event VBAT is stable ~3.9V...

Re: PCA9420 Battery detection in-progress ?

akckwang — Fri, 30 Sep 2022 03:18:16 GMT

Hi @guoweisun,

If VBAT freuency drop to ~37Hz, can pca9420 still detect battery normally?

We measured VBAT by oscilloscope,
and noticed that when wlc charger isn't aligned perfectly,
the VBAT voltage has ~0.1V drop compare to normal case,
but frequency is droped to ~37Hz.

Thanks~

Re: PCA9420 Battery detection in-progress ?

guoweisun — Mon, 03 Oct 2022 11:33:37 GMT

Vbat should be clear DC voltage, don't understand why it has the frequency in your side.

Re: PCA9420 Battery detection in-progress ?

akckwang — Tue, 04 Oct 2022 02:41:21 GMT

Hi @guoweisun,

Can pca9420 battery detection work with the "strange frequency" dc voltage?

Thanks~