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| 型号： | BQ2057TSG4 |
| 厂商： | Texas Instruments |
| 文件页数： | 15/31页 |
| 文件大小： | 0K |
| 描述： | IC LITH-ION LDO CHRG MGMT 8TSSOP |
| 标准包装： | 150 |
| 功能： | 充电管理 |
| 电池化学： | 锂离子（Li-Ion）、锂聚合物（Li-Pol） |
| 电源电压： | 4.5 V ~ 15 V |
| 工作温度： | -20°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP（0.173"，4.40mm 宽） |
| 供应商设备封装： | 8-TSSOP |
| 包装： | 管件 |
| 配用： | 296-9502-ND - EVAL MOD FOR BQ257T |
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bq2057, bq2057C
bq2057T, bq2057W
SLUS025F ? MAY 2001 ? REVISED JULY 2002
APPLICATION INFORMATION
selecting an external pass-transistor
The bq2057 is designed to work with both PNP transistor and P-channel MOSFET. The device should be chosen
to handle the required power dissipation, given the circuit parameters, PCB layout and heat sink configuration.
The following examples illustrate the design process for either device:
PNP transistor:
Selection steps for a PNP bipolar transistor: Example: V I = 4.5 V, I (REG) = 1 A, 4.2-V single-cell Li-Ion (bq2057C).
V I is the input voltage to the charger and I (REG) is the desired charge current (see Figure 1).
1. Determine the maximum power dissipation, P D , in the transistor.
The worst case power dissipation happens when the cell voltage, V (BAT) , is at its lowest (typically 3 V at the
beginning of current regulation phase) and V I is at its maximum.
Where V CS is the voltage drop across the current sense resistor.
P D = (V I ? V CS – V (BAT) ) × IREG
(7)
P D = (4.5 – 0.1 ? 3) × 1 A
P D = 1.4 W
2. Determine the package size needed in order to keep the junction temperature below the manufacturer ’s
recommended value, T (J)max . Calculate the total theta, θ ( ° C/W), needed.
D
θ
JC
+
T
(J)max
* T
P
A(max)
(8)
θ
JC
+
(150–40)
1.4
θ
JC
+ 78 ° C W
Now choose a device package with a theta at least 10% below this value to account for additional thetas
other than the device. A SOT223 package, for instance, has typically a theta of 60 ° C/W.
3. Select a collector-emitter voltage, V (CE) , rating greater than the maximum input voltage. A 15-V device will
be adequate in this example.
4. Select a device that has at least 50% higher drain current I C rating than the desired charge current I (REG) .
5. Using the following equation, calculate the minimum beta ( β or h FE ) needed:
+ CMAX
B
b
min
I
I
(9)
b
min
+
1
0.035
b
min
+ 28
where I max(C)) is the maximum collector current (in this case same as I (REG) ), and I B is the base current
(chosen to be 35 mA in this example).
NOTE:
The beta of a transistor drops off by a factor of 3 over temperature and also drops off with load.
Therefore, note the beta of device at I (REG) and the minimum ambient temperature when choosing
the device. This beta should be larger than the minimum required beta.
Now choose a PNP transistor that is rated for V (CE) ≥ 15 V, θ JC ≤ 78 ° C/W, I C ≥ 1.5 A, β min ≥ 28 and that is in a
SOT223 package.
www.ti.com
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| BQ2057TSN | 功能描述:电池管理 Li-Ion LDO Linear Charge Management IC RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| BQ2057TSNG4 | 功能描述:电池管理 LDO Lin 2-cell Li- Ion Charge Cntrlr RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| BQ2057TSNTR | 功能描述:电池管理 Li-Ion LDO Linear Charge Management IC RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| BQ2057TSNTRG4 | 功能描述:电池管理 Li-Ion LDO Linear Charge Management IC RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
| BQ2057TSTR | 功能描述:电池管理 Li-Ion LDO Linear Charge Management IC RoHS:否 制造商:Texas Instruments 电池类型:Li-Ion 输出电压:5 V 输出电流:4.5 A 工作电源电压:3.9 V to 17 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:VQFN-24 封装:Reel |
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