BQ24650: Error BTST in PCB

Hello,he

Do you have full schematic of our board?

Can you also describe your full testing conditions? Are you testing your board with a solar panel or a real power supply? Do you have any loads applied in this test? What is the battery voltage and the regulation voltage setpoint, charge current setpoint, and input voltage capability? What is the input voltage when you measure? What is the VCC voltage as compared to the SRN voltage, as measured from the pins of the charger?

And what is the waveform you captured? Is that capturing the node w.r.t. ground?

It would be beneficial to capture on a scope the PH node, the input voltage VCC, the SRN voltage, and the input or output current measurement.


Regards,
Joel H

I did my tests with 2 differents pcb with the same bench power supply(VCC 5V, 3A) and the same Li-ion battery pack (VBat=3.64V)

PCB1: Assembled by us in our lab. I've been taking measures before the charge process begin (PCB1_OFFCHG) and when the charger are working (PCB1_ONCHG)

PCB2: Assembled in China. The same SCHEMATIC, GERBER and BOM.  The main difference is you need to apply VCC= 5.32V in order to the charge process begin.

Bq24650_Sch.pdf

The next table shows all measures I took.

	PCB1_OFFCHG	PCB1_ONCHG	PCB2_OFFCHG
Vcc	4.8V	4.423V	4.8V
Vmppset	1.371V	1.371	1.465
REGN	4.8V	4.39V	4.77V
Vref	3.29V	3.29V	3.29V
TS	1.906V	1.906V	1.86V
Term_En	3.29V	3.29V	3.29V
Vbat	3.64V	3.84V	3.64V
VbatReg	4.2V	4.2V	4.2V
SRN	3.64V	3.88V	3.64V
Vfb	1.814V	1.93V	1.812V

Secondly, I've taken some caps of PCB2 in my oscilloscope.

As you can see in my first post, BTST send "ramps" periodically, however PH node doesn't change.

In the picture below you can see VCC & SRN:.

If you need more info and the complete schematic, layout I can upload it without any problem.

Regards

Anybody has an idea about what is happening?

If someone needs more info I can provide you without any problem

Hello,

It is difficult to say what is different between your two boards. If your prototype is the same as the failing board manufactured elsewhere, I am inclined to note this as a manufacturing error.

One test we can do on your non-functioning board is to drop the battery voltage during this test to see if this is the result of entering SLEEP mode. Keep your input voltage settings the same (5V), but lower the battery voltage to something like 3.0 to 3.2V and see what happens. 

Regards,

Joel H

Hello,

In the table below you can see the values of the next test.

VCC	4.78V
Vmppset	1.446V
Regn	4.78V
Vref	3.29V
TS	1.86V
Term_EN	3.29V
Vbat	3.43V
Vbat_Reg	4.2V
SRN	3.42V
vFB	1.702V

In the next picture you can see the "ramps" in BTST node 

With Vbat=3.43V the device begin to charge at Vcc=5.26V in my power supply and the btst send ramps each 1.5s aprox.

Should I supose the device is in SLEEPING MODE?

Hello,

    From the test results, BQ24650 is not in sleep mode as the condition for SLEEP is VCC-SRN < 500mV. Make sure to measure VCC and SRN on the respective pins of the IC. Your REGN voltage is a lot lower than is specified for this IC and should be between 5.7V and 6.3V with a typical value of 6V. REGN is used to drive the HSFET and LSFET. Can you check for the value of REGN on the boards of yours that were working? If REGN is so low it means IC could have been damaged. Try replacing the IC on failing boards, as well once you have measured REGN on passing boards.