Slkor SL3763: Advanced 3-Cell Lithium Battery Charging Solution

 Shenzhen Slkormicro Semicon Co., Ltd (www.slkoric.com) has a core technical team originating from Tsinghua University. With new materials, new processes, and new products driving the company’s development, Slkor has mastered world-leading third-generation semiconductor silicon carbide power device technology. Slkor is a high-tech enterprise integrating design, development, production, and sales of electronic products, providing customers with reliable products and comprehensive technical support.

 

1.1 Name: Slkor SL3763 Three-Cell Lithium Battery Charging Solution

 

1.2 Applications: Backup battery applications, handheld devices, portable industrial and medical instruments, power tools, and standalone battery chargers

 

2. Complete charging management for three-cell lithium batteries, charging current up to 4A, with over-voltage protection

 

2.1 Automatic Recharge

After charging is completed, if both the input power and battery remain connected to the charger, the battery voltage will gradually drop due to self-discharge or load consumption. When the battery voltage decreases to 95.5% of the constant-voltage charging threshold, the SL3763 automatically re-enters charging mode, initiating a new charging cycle. This ensures that the battery’s capacity is maintained above 80%.

 

When the battery is not connected, the SL3763 will charge the output capacitor to the constant-voltage charging level (or slightly higher) before stopping. Due to the discharge effect of the BAT pin’s working current on the output capacitor, the BAT pin voltage will slowly drop to the recharge threshold, prompting the SL3763 to re-enter charging mode. The charger will then cycle between charging and stop states, forming a sawtooth waveform at the BAT pin while outputting a pulse signal indicating that no battery is installed.

It is not recommended to connect the battery while the charger is running, as this may cause uncertain states or a sudden surge of current into the battery.

 

2.2 Sleep Mode Battery Current

When the input voltage is removed or lower than the battery voltage, the SL3763 enters sleep mode. The current flowing into the BAT and CSP pins is approximately 9μA (VBAT = 12V).

 

3. Application of Slkor Brand in Solar-Powered Lighting

 

Slkor provides a complete solution for solar charging and lighting, including voltage/current sampling, amplifiers with constant current sources, multi-cell lithium battery charging management, various MOSFET drivers, and phototransistors.

 

 

4. Typical Application of Slkor SL3763 in 3-Cell Lithium Battery Charging

 

 

 

 

4.1 Application Principle:

The Slkor SL3763 charging IC stores solar energy in lithium batteries, enabling automatic day/night switching, forming a small night-light driver module.

 

U8: Slkor phototransistor (SLPT0805AC) conducts under sunlight, automatically turning off the 5V supply. Thus, the Slkor SL348XT5 op-amp cannot drive the Slkor SL3400 MOSFET, and the lamp remains off during the day.

 

At night, U8 is cut off, 5VCC is enabled, and the battery powers the lamp board J2.

 

4.2 Figure 1: Slkor SL3763 lithium battery charging IC. Users can design constant-current charging levels per datasheet.

 

R1 = 40mΩ, charging current = 3A (120mV / 40mΩ).

 

Slkor SL4435: P-channel MOSFET, Rds(on) = 30mΩ @ Vgs=4.5V, Vds=30V, Id=10A, suitable for high-side switches.

 

SS56: Slkor Schottky diode, If=5A, Vr=60V, ideal for low-voltage rectification.

 

4.3 Figure 2: Slkor MOSFET SL2305S, Id=4A, Rds(on)<45mΩ @ Vgs=4.5V, SOT-23 package, suitable for switching and power path management.

 

4.4 Figure 3: Slkor LM2596S-5.0, fixed 5V DC-DC buck converter, Vin=5–30V, with minimal external circuitry.

 

4.5 Figure 4: Lamp driver circuit uses Slkor SL348XT5 op-amp (rail-to-rail I/O, low slew rate, max 40mA output) directly driving Slkor SL3400 MOSFET in a constant-current circuit. Lamp brightness can be adjusted via R19.

 

Slkor SL3400 MOSFET: Vds=30V, Id=5.8A, SOT-23 package, Vgs(th)=0.9V, ideal for low-voltage drive applications such as PWM, power management, and load switches.

 

4.6 Figure 5: In strong sunlight, Slkor SLPT0805AC-LB1 phototransistor conducts, cutting off Q7, automatically turning off the solar lamp panel during the day.

 

Key Device: Slkor SLPT0805AC-LB1 infrared phototransistor, high sensitivity, compact SMD package, reliable, energy-saving, and eco-friendly. Widely used in light-control lighting such as night lamps.

 

5. Slkor SL3763 Charging Demo Board

 

 

 

 

5.1 PCB Design Recommendations:

Good PCB design is crucial for SL3763 performance, reducing EMI, and improving efficiency. For the circuit in Figure 1, keep in mind:

 

Input filter capacitor positive terminal should be close to the P-channel MOSFET source.

 

Diode D1 should be placed near the inductor, and the current sense resistor should also be near the inductor.

 

Output capacitor should be close to the current sense resistor.

 

Keep traces short between input capacitor, P-MOSFET, D1, inductor, sense resistor, and output capacitor.

 

GND and COM pin compensation component grounds must connect directly to system ground to avoid switching noise interference. Input capacitor ground, D2 anode, and output capacitor ground should first connect to the same copper plane before returning to system ground.

 

The sense resistor R1 must be placed so that traces from CSP and BAT pins are short and on the same PCB layer for minimal distance. CSP and BAT pins should connect directly to the resistor to ensure accurate current detection.

 

 

6. BOM Information of Slkor SL3763 Charging Demo Board