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| 型号： | SI9730ABY-T1-E3 |
| 厂商： | Vishay Siliconix |
| 文件页数： | 11/15页 |
| 文件大小： | 0K |
| 描述： | IC CONTROLLR LI-ION 4.2V 8SOIC |
| 标准包装： | 2,500 |
| 功能： | 双电池控制器 |
| 电池化学： | 锂离子（Li-Ion） |
| 工作温度： | -25°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOICN |
| 包装： | 带卷 (TR) |
Product is End of Life 3/2014
Si9730
Vishay Siliconix
Output Capacitor
Depending on the MOSFET selected, the Si9730 can open
the switch quite rapidly, in a matter of a few microseconds.
However, the various monitoring operations take 10-100
times longer than this, and the basic period of the Si9730’s
oscillator is 4 msec. In order to prevent false readings by the
MOSFET Selection
Two MOSFETs in series, with their sources and gates con-
nected together, are used as the switch. This prevents cur-
rent from flowing in either direction when the gate is low; if
only one MOSFET were used, the body diode could conduct
current in the opposing direction.
Si9730, it is necessary to attach a capacitor across the out-
put of the battery charger/load (this is not in parallel with the
LITTLE FOOT
?
MOSFETs are recommended for this appli-
battery, because of the switch). A 10 μF capacitor is recom-
mended for this purpose; see Figure 8.
Selecting a Current Sense Resistor
cation, because of their size, performance and cost benefits.
SO-8 and TSSOP-8 MOSFETs allow for space efficient
designs with performance equal to or better than their DPAK
and TO-220 predecessors. Further, their availability from
multiple sources permits a cost effective solution.
The current sense resistor should be selected based on the
maximum current the battery can source or charge at; above
this current, the Si9730 will open the switch, disconnecting
the battery from its load or charger.
R sense = V ILIMIT /I ILIMIT ≈ 28 mV/I ILIMIT
Of course, the resistor must be rated to take the power dissi-
pated in it as well:
P RSENSE = I ILIMIT * V ILIMIT ≈ 28 mV * I ILIMIT
For example, suppose that the maximum current the battery
will see is 1.8 A. Then, I LIMIT might be chosen to be 2 A. We
would then select a resistor of
R SENSE = 28 mV/2 A = 14 m Ω .
The power dissipation in this resistor is
P RSENSE = 28 mV * 2 A = 56 mW
and so a 100 mW surface mount resistor would be suitable.
Another possibility is to use a thin copper trace as the
sense resistor. The copper has a temperature coefficient of
0.39 %/°C, but this is partially compensated for by the tem-
perature coefficient of the current limit comparator in the
Si9730, which is 0.18 %/°C. A simple formula for selecting a
trace to act as a current sensor is:
There are two important parameters to consider in MOSFET
selection: gate threshold voltage; and on-resistance, which
determines power dissipation.
Even when the DCO pin of the Si9730 is low, the specifica-
tion allows its value to be as high as 0.4 V. If this voltage were
close to the gate threshold voltage, leakage current through
the MOSFETs could be hundreds of microamps, which
would result in the battery quickly becoming discharged. To
ensure that leakage is minimized, N-Channel MOSFETs with
a minimum gate threshold voltage of 0.8 V should be chosen.
On resistance of the MOSFETs needs to be selected to limit
power dissipation into the MOSFETs’ package. For example,
a dual MOSFET SO-8 package is rated at 2 W, and a dual
MOSFET TSSOP-8 package is rated at 1 W (both at 25 °C;
if the ambient temperature is higher, the allowable power dis-
sipation in these packages is less). For example, if the max-
imum current is 2 A, and a dual MOSFET SO-8 package is
being used, the maximum on-resistance of the two MOS-
FETs in series must not exceed
1 W = (2 A) 2 * R ON
or R ON = 0.25 Ω ; each MOSFET can be allotted half of this,
R ON = 125 m Ω . Account must also be taken of the fact that
MOSFETs’ on-resistance is a function of temperature; a con-
servative approach would give a discount of 1/3,
R ON = 125 m Ω * (2/3) = 80 m Ω per MOSFET.
R
0.5 m Ω x
length
width
1 oz. Copper
A list of recommended MOSFETs, which Vishay Siliconix
supplies, follows.
For example, to get a 14 m Ω . resistor, we need length/width
= 28; with a trace width of 0.01", the length of the trace
should be 0.28".
Document Number: 70658
S-40135-Rev. F, 16-Feb-04
www.vishay.com
11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SI9730BBY | 功能描述:电池管理 Battery Controller 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 |
| SI9730BBY-E3 | 功能描述:电池管理 Li Batt Controller 4.20-4.30V OC Detect 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 |
| SI9730BBY-T1 | 功能描述:电池管理 Li Batt Controller 4.20-4.30V OC Detect 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 |
| SI9730BBY-T1-E3 | 功能描述:电池管理 Li Batt Controller 4.20-4.30V OC Detect 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 |
| SI9730CBY | 功能描述:电池管理 Battery Controller 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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