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參數(shù)資料
| 型號： | FAN2012I |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | 1.5A Low Voltage Current Mode Synchronous PWM Buck Regulator |
| 中文描述： | 1.5A的低電壓電流模式同步PWM降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 7/10頁 |
| 文件大?。?/td> | 240K |
| 代理商： | FAN2012I |
7
www.fairchildsemi.com
FAN2011/FAN2012 Rev. 1.0.2
F
Block Diagram
Figure 4. Block Diagram
Detailed Operation Description
The FAN2011 is a step-down pulse width modulated (PWM)
current mode converter with a typical switching frequency of 1.3
MHz. At the beginning of each clock cycle, the P-channel tran-
sistor is turned on. The inductor current ramps up and is moni-
tored via an internal circuit. The P-channel switch is turned off
when the sensed current causes the PWM comparator to trip
when the output voltage is in regulation or when the inductor
current reaches the current limit (set internally to typically
2600mA). After a minimum dead time, the N-channel transistor
is turned on and the inductor current ramps down. As the clock
cycle is completed, the N-channel switch is turned off and the
next clock cycle starts. The duty cycle is solely given by the ratio
of output voltage and input voltage. Therefore, the converter
runs with a minimum duty cycle when output voltage is at mini-
mum and input voltage is at maximum.
100% Duty Cycle Operation
As the input voltage approaches the output voltage and the duty
cycle exceeds the typical 95%, the converter turns the P-chan-
nel transistor continuously on. In this mode the output voltage is
equal to the input voltage minus the voltage drop across the P-
channel transistor:
V
OUT
R
DS_ON
=
P-channel switch ON resistance
I
LOAD
=
Output current
R
L
=
Inductor DC resistance
UVLO and Soft Start
= V
IN
–
I
LOAD
×
(R
DS_ON
+ R
L
), where
The reference and the circuit remain reset until the V
IN
crosses
its UVLO threshold.
The FAN2011 has an internal soft-start circuit that limits the in-
rush current during start-up. This prevents possible voltage
drops of the input voltage and eliminates the output voltage
overshoot. The soft-start is implemented as a digital circuit
increasing the switch current in four steps to the P-channel cur-
rent limit (2600mA). Typical start-up time for a 40μF output
capacitor and a load current of 1500mA is 800μs.
Short Circuit Protection
The switch peak current is limited cycle by cycle to a typical
value of 2600mA. In the event of an output voltage short circuit,
the device operates with a frequency of 400kHz and minimum
duty cycle, therefore the average input current is typically
350mA.
Thermal Shutdown
When the die temperature exceeds 150
°
C, a reset occurs and
will remain in effect until the die cools to 130
°
C, at that time the
circuit will be allowed to restart.
Applications Information
Setting the Output Voltage
The internal reference is 0.8V. The output is divided down by a
voltage divider, R1 and R2 to the FB pin. The output voltage is:
According to this equation, and assuming desired output volt-
age of 1.5096V, and given R2 = 10K
, the calculated value of
R1 is 8.87K
.
FB
ERROR
AMP
REF
FB
IS
CSENSE
DIGITAL
SOFT START
UNDER VOLTAGE
LOCKOUT
LOGIC
CONTROL
MOSFET
DRIVER
OSC
SLOPE COMPENSATION
COMP
OVER
VOLTAGE
COMP
IS
GND
SW
V
IN
EN
GND
0.8V
V
OUT
V
REF
1
R
1
R
2
------
+
=
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| FAN2012IMPX | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:1.5A Low Voltage Current Mode Synchronous PWM Buck Regulator |
| FAN2012MPX | 功能描述:直流/直流開關轉換器 HE step-down DC/DC converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| FAN2012MPX_Q | 功能描述:直流/直流開關轉換器 HE step-down DC/DC converter RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| FAN2013 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:2A Low-Voltage, Current-Mode Synchronous PWM Buck Regulator |
| FAN2013_08 | 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:2A Low-Voltage, Current-Mode Synchronous PWM Buck Regulator |
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