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EUP8054XOIR1 参数 Datasheet PDF下载

EUP8054XOIR1图片预览
型号: EUP8054XOIR1
PDF下载: 下载PDF文件 查看货源
内容描述: 独立线性锂离子电池充电器采用ThinSOT封装的热调节 [Standalone Linear Li-Ion Battery Charger With Thermal Regulation in ThinSOT]
分类和应用: 电源电路电池电源管理电路
文件页数/大小: 17 页 / 432 K
品牌: EUTECH [ EUTECH MICROELECTRONICS INC ]
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EUP8054/8054X  
Application Information  
Stability Considerations  
Power Dissipation  
The conditions that cause the EUP8054 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:  
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 1resistor in  
series with the capacitor. No series resistor is needed if  
tantalum capacitors are used.  
PD=(VCCVBAT) IBAT  
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:  
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,  
TA=120-PDθ  
JA  
TA=120-(VCC-VBAT)IBAT θ  
JA  
Example: An EUP8054 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.  
C
PROG, the following equation can be used to calculate  
the maximum resistance value for RPROG  
:
Assuming  
θ
is 150/W (see Board Layout  
ConsiderationsJA), the ambient temperature at which the  
EUP8054 will begin to reduce the charge current is  
approximately:  
1
R
PROG  
5
2π10 C  
PROG  
TA=120-(5V-3.75V)(400mA)150/W  
TA=120-0.5W150/W=120℃-75℃  
TA=45℃  
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 8. A 10k  
resistor has been added between the PROG pin and the  
filter capacitor to ensure stability.  
The EUP8054 can be used above 45ambient, but the  
charge current will be reduced from 400mA. The  
approximate current at a given ambient temperature can  
be approximated by:  
120°C T  
A
I
=
BAT  
(
V
V  
BAT  
)
• θ  
CC  
JA  
Using the previous example with an ambient temperature  
of 60, the charge current will be reduced to  
approximately:  
120°C 60°C  
5V 3.75V 150°C / W 187.5°C / A  
= 320mA  
60°C  
I
I
=
=
BAT  
BAT  
(
)
Moreover, when thermal feedback reduces the charge  
current, the voltage at the PROG pin is also reduced  
proportionally as discussed in the Operation section.  
It is important to remember that EUP8054 applications  
do not need to be designed for worst-case thermal  
conditions since the IC will automatically reduce power  
dissipation when the junction temperature reaches  
approximately 120.  
Figure 8. Isolating Capacitive Load on PROG Pin  
and Filtering  
DS8054 Ver1.1 Jan. 2007  
13