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BQ24707 参数 Datasheet PDF下载

BQ24707图片预览
型号: BQ24707
PDF下载: 下载PDF文件 查看货源
内容描述: 1-4节锂电池SMBus充电控制器具有独立的比较器和先进的电路保护 [1-4 Cell Li Battery SMBus Charge Controller With Independent Comparator and Advanced Circuit Protection]
分类和应用: 电池比较器电路保护控制器
文件页数/大小: 36 页 / 1269 K
品牌: TI [ TEXAS INSTRUMENTS ]
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bq24707  
bq24707A  
SLUSA78B JULY 2010REVISED MARCH 2011  
www.ti.com  
D1  
R2(1206)  
10-20 Ω  
R1(2010)  
2Ω  
Adapter  
connector  
VCC pin  
C1  
2.2μF  
C2  
0.47-1μF  
Figure 20. Input Filter  
IC Design Guideline  
The IC has a unique short circuit protection feature. Its cycle-by-cycle current monitoring feature is achieved  
through monitoring the voltage drop across Rdson of the MOSFETs after a certain amount of blanking time. In  
case of MOSFET short or inductor short circuit, the over current condition is sensed by two comparators and two  
counters will be triggered. After seven times of short circuit events, the charger will be latched off. The way to  
reset the charger from latch-off status is reconnect adapter. Figure 21 shows the IC short circuit protection block  
diagram.  
Adapter  
ACN  
BTST  
ACP  
SCP1  
RAC  
High-Side  
MOSFET  
RPCB  
PHASE  
L
REGN  
RDC  
Battery  
Low-Side  
MOSFET  
COMP1  
SCP2  
COMP2  
C
Count to 7  
CLR  
Latch off  
Charger  
Adapter  
Plug in  
Figure 21. Block Diagram of IC Short Circuit Protection  
In normal operation, low side MOSFET current is from source to drain which generates negative voltage drop  
when it turns on, as a result the over current comparator can not be triggered. When high side switch short circuit  
or inductor short circuit happens, the large current of low side MOSFET is from drain to source and can trig low  
side switch over current comparator. IC senses low side switch voltage drop by PHASE pin and GND pin.  
The high-side FET short is detected by monitoring the voltage drop between ACP and PHASE. As a result, it not  
only monitors the high side switch voltage drop, but also the adapter sensing resistor voltage drop and PCB trace  
voltage drop from ACN terminal of RAC to charger high side switch drain. Usually, there is a long trance between  
input sensing resistor and charger converting input, a careful layout will minimize the trace effect.  
26  
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© 20102011, Texas Instruments Incorporated  
Product Folder Link(s): bq24707 bq24707A  
 
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