SLM6305 4.2V2A Wide Input Charger

Advantages of the SLM6305 solution:
1. Wide input
voltage range: 5-26V, can be powered by USB, a standard 12V adapter, and 24V.
2. High charging current:
Maximum charging current can be set to 2.5A.
3. Compact size:
With optimized layout, it is comparable to or even smaller than the TP4506 solution.
Item Parameters:
Input Voltage: 12V;
Charging Cut-off Voltage: 4.2V;
Charging Current: 2A;
Supports NTC.
Main Component Parameters:
C1-C4: Input filter, total capacity recommended to be 30UF or higher, 310UF or 222UF can be used, 25V capacitor can be used if the input voltage is less than 15V.
C5: Internal driver capacitor, 0.1UF 50V X7R or higher, 25V capacitor can be used if the input voltage is less than 15V.
R1 & R2: Chip charging indicator current limiting resistor, official recommendation 1K, LED too bright under high voltage input conditions, 2K or 4.7K recommended.
For L1, an inductor of 6.8-10uH is selected. The charging circuit does not require excessively high dynamic response; commercially available circuits typically use 4.7uH inductors, which can lead to significant chip heat generation. This project uses an inductor to meet the 2A and 2.5A charging current requirements
. For R3 and R4, based on charging currents of 1A = 67mΩ, 1.5A = 44mΩ, 2A = 33mΩ, and 2.5A = 27mΩ, considering PCB layout requirements and resistor power, two 0805 package resistors are used in parallel to distribute the power and meet the project requirements. For a charging current of 2.5A, three 0805 package resistors need to be used in parallel to ensure that the rated power of the resistors is not exceeded
. The overall resistance value of the resistors cannot be less than 26.7mΩ; otherwise, the nominal 2.5A current will be exceeded.
R5 and R6 are NTC resistors. If the NTC function is not used, R5 or R6 should be a 1MΩ resistor; leaving them floating is not recommended. Using the NTC function, select 10K B3950K resistors
C6-C8. The total output capacitor capacitance should be less than 30uF.
For more design requirements, please refer to the datasheet.
During charging, there is no heat generation
at
an input voltage of 5V, noticeable heat generation at 12V, and significant heat generation at 24V.