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AAT1142 参数 Datasheet PDF下载

AAT1142图片预览
型号: AAT1142
PDF下载: 下载PDF文件 查看货源
内容描述: 800毫安电压缩放降压型转换器 [800mA Voltage-Scaling Step-Down Converter]
分类和应用: 转换器
文件页数/大小: 22 页 / 975 K
品牌: ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
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AAT1142  
800mA Voltage-Scaling Step-Down Converter  
rate output regulation. Output regulation is main-  
tained until the dropout voltage, or minimum input  
voltage, is reached.  
sation terminates the transconductance voltage  
error amplifier output. Loop stability and fast tran-  
sient response are maintained across the entire  
input and output voltage range with a small 2.2µH  
output inductor and 10µF output capacitor.  
The AAT1142 achieves better than ±0.5% output  
regulation across the input voltage and output load  
range. Maximum continuous load is 800mA. A  
current limit of 1A (typical) protects the IC and sys-  
tem components from short-circuit damage.  
Typical no load quiescent current is 35µA.  
Soft Start/Enable  
Soft start limits the current surge seen at the input  
and eliminates output voltage overshoot. When  
pulled low, the enable input forces the AAT1142  
into a low-power, non-switching state. The total  
input current during shutdown is less than 1µA.  
The turn-on time from EN to output regulation is  
100µs (typical).  
Thermal protection completely disables switching  
when the maximum junction temperature is detect-  
ed. The junction over-temperature threshold is  
140°C with 15°C of hysteresis. Once an over-tem-  
perature or over-current fault condition is removed,  
the output voltage automatically recovers.  
Alternatively, the EN/SET pin serves as the input  
for S2Cwire single line control. Details of S2Cwire  
operation and timing diagrams are provided in the  
Applications Information section of this datasheet.  
Peak current mode control and optimized internal  
compensation provide high loop bandwidth and  
excellent response to input voltage and fast load  
transient events. The output voltage is stable across  
all operating conditions, ensuring fast transitions  
with no overshoot or ringing. Soft start eliminates  
output voltage overshoot when the enable or the  
input voltage is applied. Under-voltage lockout pre-  
vents spurious start-up events.  
Current Limit and Over-Temperature  
Protection  
Switching is terminated after entering current limit  
for a series of pulses to minimize power dissipation  
and stresses under overload and short-circuit con-  
ditions. Switching is terminated for seven consecu-  
tive clock cycles after a current limit has been  
sensed for a series of four consecutive clock cycles.  
Control Loop  
The AAT1142 is a peak current mode step-down  
converter. The current through the P-channel  
MOSFET (high side) is sensed for current loop  
control, as well as short-circuit and overload pro-  
tection. A fixed slope compensation signal is added  
to the sensed current to maintain stability for duty  
cycles greater than 50%. The peak current mode  
loop appears as a voltage-programmed current  
source in parallel with the output capacitor.  
Thermal protection completely disables switching  
when internal dissipation becomes excessive. The  
junction over-temperature threshold is 140°C with  
15°C of hysteresis. Once an over-temperature or  
over-current fault condition is removed, the output  
voltage automatically recovers.  
Under-Voltage Lockout  
Internal bias of all circuits is controlled via the VIN  
input. Under-voltage lockout (UVLO) guarantees  
sufficient VIN bias and proper operation of all inter-  
nal circuitry prior to activation.  
The output of the voltage error amplifier programs  
the current mode loop for the necessary peak  
switch current to force a constant output voltage for  
all load and line conditions. Internal loop compen-  
1142.2006.07.1.0  
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