In one of our m10a PDAs, TI's bq24074 is used. The following phenomena are found. The attachment is the circuit schematic diagram of m10a. Please help us to guide whether we pay attention to the use of bq24074.
1. Unplug the charger during the charging process, and the power will jump to 100% immediately. (the temporary solution can delay reading the power of the electricity meter. But what causes the triggering and filling conditions are not found (the probability of occurrence is 100%. The precondition is that when two charging chips are installed, but the handle battery is not installed, it must be found. The state that only the handle battery is installed but not the host battery is to be verified. When the handle battery voltage is very low (2.8V), it will also appear 100%. The handle battery power is sampled by ADC)
2. In the case of natural battery depletion (at this time, the starting voltage is not accurately measured, and it is estimated that it enters the 2.0 ~ 3.0V working range), plug in the external power supply, and m10a repeatedly enters the small system restart: do not enter the icon of system startup. But the machine can be charged normally. Press the reset key to power down and restart the core module, the phenomenon will not be eliminated. Unplug the battery and then install it. The phenomenon disappears.
3. After charging, if you do not unplug the external power supply and run the application program, the m10a machine will always display 100% power, which can be used normally, but at this time, the external power supply will not charge the machine or provide power. Until the battery runs out, the machine will shut down automatically. After the shutdown, the indicator light will flash red and green alternately, but the machine will not be charged. (two lights can't be charged when they flash, one is green, and the other is flashing.) But as long as the external power is unplugged and plugged in, it can be charged again.
4. The battery is full, but the indicator light does not jump green all the time. The actual battery voltage is 4.17v (full). When the battery is unplugged, the green light will be on when it is plugged in. Probability of occurrence 1 / 100
1) When there is no battery, the charger will perform the battery test procedure by injecting current into the battery pin entering the capacitor. This will cause the capacitor to charge to vbatreg and discharge.
[reply] without unplugging the charger, the capacitor is charged to vbatreg and discharged. At this time, the charging chip thinks that the outside "battery" is full and stops charging. When the discharge voltage is lower than 4.1V (Vbat < vchg), the charging chip will start charging again. That's right.
2) Can you provide more details about charger performance here. What is small system restart? What triggered it?
[reply] the charger is a small module of 220V AC input to DC 5V / 3A output. The 5V output can supply power to the m10a machine as the input power of the internal charging chip bq24074 of the machine.
Small system restart: press the power on button for 2 seconds, the motor in the whole machine vibrates, the screen has the power on screen, the program runs to the kernel part, but Android has not started yet. After that, the screen goes off repeatedly, the motor vibrates, and the screen starts to restart repeatedly.
Now it is in the positioning analysis that the abnormal state of the device causes the whole machine to restart repeatedly and cannot enter the startup interface.
3) What is the output voltage here when there is an external power supply
[reply] the external power supply is the charger of 220V AC to DC 5V / 3a in the second reply above. The output is 5V, which is the input power of the internal charging chip bq24074 of the whole machine.
4) What controls the green light?
[reply] the PGOOD pin output of charging chip bq24074 controls the green light, the low level green light is on, and the high level green light is off.
The m10a product uses the bq24074 charging chip. In the circuit design, the out pin output is not used as the system power supply, but the battery is hung at the foot of the bat tube and the power is supplied to the whole single board system.
What's the problem with this design?
