data/text/DLP2/890769

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

Part Number: BQ24070 Hello! 1. Please can you help me to check my schematic and understand BQ24070 behavior in charge termination mode? The problem is charge termination status is not activated for hours (checked for 10h at least) on fully charged battery or w/o battery connected. I didn't ever saw any other status than STAT1=ON and STAT2=OFF. Control resistors are adjusted to the values: Rdppm=37k, Rset=3.54k, Rtmr=50k. Voltage at ISET1 pin and battery charge current are goes to zero at the end of charge and Vbat is 4.21V if no load connected (as red cross on the drawing show). 2. When I add a payload with a step-up converter (U2 L6920D) I also faced with a sort of interference on BQ24070. I get a voltage drop about 0.4V at BQ24070 OUT pin at each step-up converter cycle (see the diagram below). In that case, I have a noise about 50mV at ISET1 pin and battery final voltage increase on 0.01V. And I have no idea how to handle with that voltage drops caused by step-up converter. Please give me a guess. Best regards, Dmitry

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