BQ25606: doesn’t charge

Hendrik Bruer

Part Number: BQ25606

Hello I build the following circuit following the example given in the datasheet and tried to test it. For unknown reasons it isn’t charging the battery. To the contrary it discharges the battery, with nothing connected to SYS.

To test this circuit it was solder on an experimental board. K5 was replaced with a 10k resistor. Vusb is provided by a lab power supply, set on 5V. For the battery a 2000mAh LiPo is used, with a voltage of 3,9V.

The circuit shows following behavior:

Without battery:

PG_N, Stat: blinking simulate. 800ms high 500ms low

Vbat: ripples 4,2V-3,8V rise 50ms fall 850ms

Vsys: same as Vbat

With battery

STAT: high

PG_N: short dim flashes. 2400ms between flashes

Vbat = battery voltage

Vsys = battery voltage

Am I missing something? Any input would be helpful.

Thank you

over 4 years ago

0 Ning T over 4 years ago

TI__Guru 57741 points

Hi,

Please visit https://e2e.ti.com/support/power-management/f/196/t/890626 for BQ25606: Schematic Review and PCB Layout Design Tips.

Additional Information including FAQs is available http://www.ti.com/lit/an/slva924/slva924.pdf Designing A Standalone Single Cell 3-A Charger with the bq25606.

/PG should stay low in order to charge normally. Please check VBUS pin voltage and see if VBUS voltage is above 3.9V all the time.

Please check if STAT pin indicate any faults and debug from there. STAT pin blinks 1Hz when Charge suspend (input overvoltage, TS fault, timer fault or system overvoltage, battery overvoltage)

Please also check if the input source is over-loaded, either the current exceeds the input current limit or the VBUS pin voltage falls below the input voltage limit.

Thanks,

Ning.

0 Hendrik Bruer over 4 years ago in reply to Ning T

Prodigy 50 points

Hello,

Thank you for the help. Sadly it doesn’t help.

I replaced the resistors connected to TS with tow 10k resistors, one connected to GND the other connected to REGN.
There was no change in the circuit´s behavior.

I checked VBUS. It stays above 3,9V, its stable at 5,2V.

STAT still blinks, but not with 1Hz. Furthermore I checked for all faults, none of them were given.
                Input Voltage = 5,2V.
                TS -> connected to GND and REGN with 10k resistors.
                Timer fault -> unlikely, device was never active for more than some minutes.
                System voltage = 3,9V (with battery attached, without ripples between 4,2V and 3,8V)
                battery voltage = 3,9V (with battery attached, without ripples between 4,2V and 3,8V)

Input current never exceeded 20mA and ILIM is set to 3,125A (=500A*R/160R)

Compared both datasheets with the build circuit. There are no differences.

Best regrades

Hendrik Bruer

0 Ning T over 4 years ago in reply to Hendrik Bruer

TI__Guru 57741 points

Hendrik,

Please check if the STAT pin pull-up source is stable or not.

Thanks,

Ning.

0 Hendrik Bruer over 4 years ago in reply to Ning T

Prodigy 50 points

Ning,

Pull-up source STAT pin is stable, it is VUSB.

Best regards

Hendrik Bruer

0 Ning T over 4 years ago in reply to Hendrik Bruer

TI__Guru 57741 points

Hendrik,

/PG high indicates power not good. Did you monitor the VBUS pin voltage (measured at VBUS pin of the charger IC)?

Thanks,

Ning

0 Hendrik Bruer over 4 years ago in reply to Ning T

Prodigy 50 points

Ning,

I monitored VUSB Pin as close as possible to the IC and it is stable, ripples is smaller than 10mV.

Best regards

Hendrik Bruer

0 Ning T over 4 years ago in reply to Hendrik Bruer

TI__Guru 57741 points

Hendrik,

Is VBUS pin voltage similar to BAT pin voltage?

Thanks,

Ning.

0 Hendrik Bruer over 4 years ago in reply to Ning T

Prodigy 50 points

Ning,

They are not similar. VBUS is stable at 5.2V with or without battery attached.

BAT ripples between 4.2 and 3.8 if no battery is attached and with a battery attached BAT is equal to the battery voltage, 3.9V, and stable.

Best regards

Hendrik Bruer

0 Ning T over 4 years ago in reply to Hendrik Bruer

TI__Guru 57741 points

Hendrik,

Will get back during business hours in the next week.

Thanks,

Ning

0 Ning T over 4 years ago in reply to Ning T

TI__Guru 57741 points

Hi,

Please try a new fresh IC and/or another fresh board and see if it works.

Thanks,

Ning.

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BQ25606: doesn’t charge