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參數(shù)資料
| 型號： | LSP4054CLAD |
| 廠商： | LITE-ON SEMICONDUCTOR CORP |
| 元件分類： | 電源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數(shù)： | 17/17頁 |
| 文件大?。?/td> | 634K |
| 代理商： | LSP4054CLAD |
Liteon Semiconductor Corporation
LSP4054
Standalone Linear Li-ion Battery Charger with Thermal Regulation
Rev1.1
9/17
Figure 4: Charge current vs RCC
VCC Bypass Capacitor
Many types of capacitors can be used for input bypassing, however, caution must be exercised when using
multilayer ceramic capacitors. Because of the self-resonant and high Q characteristics of some types of ceramic
capacitors, high voltage transients can be generated under some start-up conditions, such as connecting the
charger input to a live power source. Adding a 1.5W resistor in series with an X5R ceramic capacitor will minimize
start-up voltage transients. For more information, refer to Application Note 88.
Charge Current Soft-Start
The LSP4054 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. When a charge
cycle is initiated, the charge current ramps from zero to the full-scale current over a period of approximately 100ms.
This has the effect of minimizing the transient current load on the power supply during start-up.
CHRG Status Output Pin
The CHRG pin can provide an indication that the input voltage is greater than the undervoltage lockout threshold
level. A weak pull-down current of approximately 20mA indicates that sufficient voltage is applied to VCC to begin
charging. When a discharged battery is connected to the charger, the constant current portion of the charge cycle
begins and the CHRG pin pulls to ground. The CHRG pin can sink up to 10mA to drive an LED that indicates that a
charge cycle is in progress.
When the battery is nearing full charge, the charger enters the constant-voltage portion of the charge cycle and the
charge current begins to drop. When the charge current drops below 1/10 of the programmed current, the charge
cycle ends and the strong pull-down is replaced by the 20mA pull-down, indicating that the charge cycle has ended.
If the input voltage is removed or drops below the undervoltage lockout threshold, the CHRG pin becomes high
impedance. Figure 5 shows that by using two different value pull-up resistors, a microprocessor can detect all three
states from this pin.
Figure 5: Microprocessor to determine CHRG state
To detect when the LSP4054 is in charge mode, force the digital output pin (OUT) high and measure the voltage at
the CHRG pin. The N-channel MOSFET will pull the pin voltage low even with the 2k pull-up resistor. Once the
charge cycle terminates, the N-channel MOSFET is turned off and a 20mA current source is connected to the
CHRG pin. The IN pin will then be pulled high by the 2k pull-up resistor. To determine if there is a weak pull-down
current, the OUT pin should be forced to a high impedance state. The weak current source will pull the IN pin low
through the 800k resistor; if CHRG is high impedance, the IN pin will be pulled high, indicating that the part is in a
UVLO state.
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