The peripheral circuit is simple and does not require an external MOS
Programmable charging current, maximum 0.3A@5V
Low standby current, FM9689 standby current is about 6uA
Full charge voltage optional, floating charge voltage accuracy ± 1%

Soft start function
Trickle current/constant current/constant voltage three-stage charging
Can achieve maximum 0.5A@5V Boost output
The overall plan can achieve a maximum efficiency of 90% in boosting voltage
After the input power is turned on, the battery will automatically boost and supply power in case of power failure

Multiple protection designs such as output current limiting protection and short circuit protection
Turn off the boost function during no-load detection, and the default current value for no-load judgment is about 7mA
No load judgment current 1~7mA, adjustable in multiple levels
Can drive 2 LEDs to indicate charging and discharging status
Support charging DATA protocol
FM9689 provides SOP8 packaging

TWS wireless Bluetooth earphone charging case
Other portable devices

    CBAT, COUP, and CVIN capacitors are filtering capacitors that can use ceramic capacitors. It is recommended to choose 10V for voltage resistance, as increasing the capacitance value will make the system more stable. In any case, choosing capacitors with poor quality may cause a decrease in overall system performance, shortened service life, or even malfunction, so please choose capacitors carefully.

    It is recommended to use shielded inductors, but unshielded inductors can also be used to reduce costs. If the inductance value is 2.2uH, different inductance values will affect the no-load detection current. Please refer to the measured data for accuracy.

    Due to the addition of two-stage short-circuit protection on the chip, there are certain requirements for the boost load test:
    If the USB is connected to a large capacitive load (some models of load gauges have very large capacitors), it is possible to misjudge the short-circuit protection.
When simulating a battery with a voltage source, the transient response of various types of power sources may be different, and the impedance of the power line may also be relatively high. Short circuit protection may also occur when boosting with CC or CR load or starting with load. In practical applications, the situation of CC or CR will be improved due to the connection of the battery. Generally, the input capacitance of portable devices is relatively small, and they will detect the input voltage. If the input voltage is not enough, they will not charge, so there will be no misjudgment or short circuit when charging portable devices with mobile power products.

1. High current circuit
    The high current circuit refers to the devices and wiring that carry high currents during switching. In this system, it consists of L1, CBAT, COUP, and their connections. Their wiring should be as wide and short as possible. The high-frequency switch (current discontinuous) path should not pass through the through-hole, and CBAT and L1 must be on the same side of the PCB and placed together.

2.GND

    The OUT and GND pins of FM9689 are respectively the power supply and ground of the chip driving part. During the operation of the switch, there will be instantaneous large currents flowing in and out. Therefore, when drawing the PCB, the negative terminal of CBAT and GND should be as close as possible and not through holes.

3. Placement of capacitors

    All capacitors must be placed close to the chip.
4. WTP wiring
    Pay attention to bypassing inductor L1 when routing WTP to avoid interference.