BQ24070: BQ24070: No charge termination status is activated and interference with step-up converter on payload side

Hi Dmitry,

Just to get a better understanding of your problem, is the information you provided for when ISET2 and MODE are HIGH or LOW? 

Hi Anthony,

thank you for reply! ISET2 and MODE are both HIGH for my setup.

Best regards, Dmitry

Hello,

WHat is the state of MOde and ISET2?

Hi Raheem,

thank you for reply! ISET2 and MODE are both HIGH for my setup.

Best regards, Dmitry

Hi Dmitry,

Just to check that the device is operating correctly, as I don't think I see any problems with your schematic, does the device show proper current when in fast charge mode (for instance when the battery is a 3.5V)?

Hi Anthony,

yes it is. I have discharge my battery down to 3.4V, switch on DC supply, and check battery charge current. It was constant 0.3A as it should be for my Rset value, till ~4V at the battery. I left my setup switched on during the night and have found at the next morning both status LEDs are off, so finally charging was stopped by timer for the first time. But I still had a small charging current about 1mA at my battery and voltage was about 4.3V. Then I made just an off-on cycle at DC supply and have got STAT1=ON signal again for a whole day as usual. But charge current is zero now. It looks like completely broken logic, but I can't understand why. I'm continue some more experiments...

Best regards, Dmitry

Dmitry,

Would you be able to monitor the voltage TMR pin and see how that is operating as the current drops below 30mA (calculated termination current)? Do you also see the same behavior with higher RSET values? 

Anthony,

I repeated a charge cycle today (but disconnected a payload from BQ24070 now, pure charger). Voltage at TMR pin was 2.51V from the beginning of current regulation phase till Vbat rised about 4.1V and then it began to drop down to 722mV on fully charged battery. V_TMR was 725mV when charge current dropped below 30mA. In this cycle STAT1 signal stalled again, I waited 12 hours and it still show charging, but charge current is zero now. I will increase charge current from 0.3A to 0.6A tomorrow and test it again.

UPDATE: I have increased charge current twice to 0.6A - absolutely the same voltage at TMR pin as I described above. STAT1 signal went OFF after 10 hours indicating charge time is out. Charge current is zero. No indication of finished charge by STAT2.

Best Regards, Dmitry

Hello,

Can you swap out the battery and use a sourcemeter instead on BAT pin

WHat voltage do you measure on ISET1 pin when the battery voltage is around 4.2V?

Also, can you try removing the C4 capacitor and see if that makes a difference?

From the schematic, can you have the LEDs be pulled up to OUT instead of IN

Hello, Raheem!

Can you swap out the battery and use a sourcemeter instead on BAT pin

Sorry, I don't have this type of tool. But I checked charge cycle with two different batteries: 1000mAh flat LiPo protected cell and 18650 2200mAh unprotected NCM cell. In both cases BQ behaves absolutely same.

WHat voltage do you measure on ISET1 pin when the battery voltage is around 4.2V?

0V (zero)

Also, can you try removing the C4 capacitor and see if that makes a difference?

No difference.

From the schematic, can you have the LEDs be pulled up to OUT instead of IN

I just performed this modification: nothing changed.

Best regards, Dmitry

Hi all!

Finally I have found the source of my troubles. It is related to DPPM function of BQ24070. For some reason device is not functioning properly for "Charge Done" status detection if the voltage at DPPM pin is set more than 3.71V. Even if my payload is disconnected. I have lowed DPPM pin voltage down to 3.65V and have got working "Charge Done" status detection with payload disconnected.

But it wasn't enough to work properly with my payload (a step-up converter and a MCU). I still had a big voltage drops on BQ24070 OUT pin at each converter cycle. Then I have increased C8 up to 330uF and that lowed drops amplitude 4 times. Finally, this helped to get "Charge Done" status with my payload connected to the BQ24070.

Still have no idea, why it doesn't work properly with DPPM pin voltage set higher than 3.71V. Any ideas?

Best regards, Dmitry

Hello,

this sounds reasonable. But is it normal when BQ24070 loosing "Charge done" detection capability if it have no any payload and V_DPPM is set to more than 3.71V ? I powering my setup from the 5V 5A lab power supply, set a 0.6A battery charge current and do not see any meaningful noise at BAT and OUT pins. And BQ24070 still stalling with the charge status till timeout happens.

Best regards, Dmitry