Slkor SL4054 Constant-current/Constant-voltage Linear Charger for Single Cell Lithium-ion Batteries
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1.1. Title: Slkor® SL4054 Linear Li-Ion Charger
1.2. Applications:
USB-Powered Charging, Handheld Computers, MP3 Players, Bluetooth Headphones, Digital Cameras, Cellular Telephones, PDA.
1.3. Description:
The Slkor®4054 is a complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries. Its SOP package and low external component count make the SL4054 ideally suited for portable applications. Furthermore, the SL4054 can work with USB and wall adapters. No blocking diode is required due to the internal PMOSFET architecture and has prevented to a negative Charge Current Circuit. Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. The charge voltage is fixed at 4.2V, and the charge current can be programmed externally with a single resistor. The SL4054 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached. When removing input power automatically puts the SL4054 into a low current mode to reduce the battery's leakage current to below 2uA, and the shutdown mode reduces the supply current to 45µA. SL4054 Other features include a current monitor, under voltage lockout, automatic recharge, and two status pins to indicate charge termination and the presence of an input voltage. The Slkor® SL4054 is available in a SOT23-5 (ThinSOTTM) package.
2. Slkor® SL4054 Typical Application Circuit:
Fig.1
3.1. Charging Cycle:
When the voltage on the Vcc pin rises above the UVLO threshold level and a precision 1% setting resistor is connected between the PROG pin and GND pin, or when a battery is connected to the charger output, the charging cycle begins. If the voltage on the BAT pin is below 2.9V, the charger enters trickle charging mode. In this mode, the SL4054 provides approximately 1/10 of the set charging current to raise the current voltage to a safe level for full-current charging. When the voltage on the BAT pin rises above 2.9V, the charger enters constant current mode and supplies a constant charging current to the battery. When the voltage on the BAT pin reaches the final float charge voltage (4.2V), the SL4054 enters constant voltage mode and the charging current starts to decrease. The charging cycle ends when the charging current drops to 1/10 of the set value.
3.2. Constant Charge Current Setting:
Charge current is set by connecting a resistor RISET from PROG(Pin 5) to GND. The value of the resistor and the charging current are calculated as follows: (determine the resistance value of the resistor based on the desired charging current).
3.3. Charging Termination:
When the charging current reaches the final float voltage and decreases to 1/10 of the set value, the charging cycle is terminated. This condition is detected by monitoring the PROG pin using an internal filtering comparator. When the voltage on the PROG pin drops to 100mV, the charging is terminated. The charging current is cut off, and the SL4054 enters standby mode, with the input power current dropping to 45uA.
3.4. Undervoltage Lockout:
An internal undervoltage lockout (UVLO) circuit monitors the input voltage and keeps the charger in shutdown mode until VCC rises above the UVLO threshold. If the UVLO comparator experiences a transition, the charger will not exit shutdown mode until Vcc rises above the battery voltage by 100mV.
4. BOM for Slkor® SL4054 Typical Application
Table.1
Notes:
1. The operating current of the chip includes the current consumed by the external resistor connected to the PROG pin (approximately 100uA), but it does not include the current used by the chip to charge itself through the BAT pin (approximately 100mA).
2. The termination current for charging is typically 0.1 times the set charging current.
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