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参数资料
| 型号： | LSP4054CLAD |
| 厂商： | LITE-ON SEMICONDUCTOR CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO5 |
| 封装： | SOT-23, 5 PIN |
| 文件页数： | 15/17页 |
| 文件大小： | 634K |
| 代理商： | LSP4054CLAD |
Liteon Semiconductor Corporation
LSP4054
Standalone Linear Li-ion Battery Charger with Thermal Regulation
Rev1.1
7/17
APPLICATION INFORMATION
Stability Considerations
The constant-voltage mode feedback loop is stable without an output capacitor provided a battery is connected to
the charger output. With no battery present, an output capacitor is recommended to reduce ripple voltage. When
using high value, low ESR ceramic capacitors, it is recommended to add a 1W resistor in series with the capacitor.
No series resistor is needed if tantalum capacitors are used. In constant-current mode, the PROG pin is in the
feedback loop, not the battery. The constant-current mode stability is affected by the impedance at the PROG pin.
With no additional capacitance on the PROG pin, the charger is stable with program resistor values as high as 20k.
However, additional capacitance on this node reduces the maximum allowed program resistor. The pole frequency
at the PROG pin should be kept above 100kHz. Therefore, if the PROG pin is loaded with a capacitance, CPROG, the
following equation can be used to calculate the maximum resistance value for RPROG:
Average, rather than instantaneous, charge current may be of interest to the user. For example, if a switching power
supply operating in low current mode is connected in parallel with the battery, the average current being pulled out of
the BAT pin is typically of more interest than the instantaneous current pulses. In such a case, a simple RC filter can
be used on the PROG pin to measure the average battery current as shown in Figure 2. A 10k resistor has been
added between the PROG pin and the filter capacitor to ensure stability.
Figure 2: Isolating capacitive load on PROG pin and filtering
Power Dissipation
The conditions that cause the LSP4054 to reduce charge current through thermal feedback can be approximated by
considering the power dissipated in the IC. Nearly all of this power dissipation is generated by the internal MOSFET
-this is calculated to be approximately:
where PD is the power dissipated, VCC is the input supply voltage, VBAT is the battery voltage and IBAT is the charge
current. The approximate ambient temperature at which the thermal feedback begins to protect the IC is:
Example: An LSP4054 operating from a 5V USB supply is programmed to supply 400mA full-scale current to a
discharged Li-Ion battery with a voltage of 3.75V. Assuming θJA is 150°C/W, the ambient temperature at which
the LSP4054 will begin to reduce the charge current is approximately:
The LSP4054 can be used above 45°C ambient, but the charge current will be reduced from 400mA. The
approximate current at a given ambient temperature can be approximated by:
Using the previous example with an ambient temperature of 60°C, the charge current will be reduced to
approximately:
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