參數(shù)資料
型號： IR3638SPBF
廠商： International Rectifier
英文描述： HIGH FREQUENCY SYNCHRONOUS PWM BUCK CONTROLLER FOR TRACKING APPLIACTIONS
中文描述： 高頻同步PWM降壓控制器進行跟蹤APPLIACTIONS
文件頁數(shù)： 8/15頁
文件大小： 300K
代理商： IR3638SPBF
IR3638SP
b
F
3/19/07
Soft-Start
The IR3638 has programmable soft-start to
control the output voltage rise and limit the inrush
current during start-up.
To ensure correct start-up, the soft-start
sequence initiates when Vcc and Enable rise
above their threshold and generate the Power On
Ready (POR) signal. The soft-start function
operates by sourcing current to charge an
external capacitor to about 3V.
Initially, the soft-start function clamps the output
of error amplifier by injecting a current (64uA)
into the Fb pin and generates a voltage about
1.6V (64ux25K) across the negative input of error
amplifier (see figure 6).
The magnitude of the injected current is inversely
proportional to the voltage at the soft-start pin. As
the soft-start voltage ramps up, the injected
current decreases linearly and so does the
voltage at negative input of error amplifier.
When the soft-start capacitor is around 1V, the
voltage at the negative input of the error amplifier
is approximately 0.8V (32uAx25K).
As soon as the Fb reaches the Vp voltage, the
output of error amplifier will start increasing and
generating the first PWM signal. As the soft-start
capacitor voltage continues to ramp up, the
current flowing into the Fb pin will keep
decreasing.
The feedback voltage increases linearly as the
soft start voltage ramps up. When soft-start
voltage is around 2V the output voltage is
reached the steady state and the injected current
is zero.
Figure 7 shows the theoretical operational
waveforms during soft-start.
The output voltage start-up time is the time
period
when
soft-start
increases from 1V to 2V.
The start-up time will be dependent on the size of
the external soft-start capacitor and can be
estimate by:
T
μ
A
22
=
capacitor
voltage
Fig. 6: Soft-Start circuit for IR3638
Fig. 7: Theoretical operation waveforms
during soft-start
22uA
64uA
POR
Error Amp
SS/SD
Fb
Comp
25K
Vp
25K
3V
Soft-Start
Voltage
Voltage at negative input
of Error Amp
Voltage at Fb pin
Current flowing
into Fb pin
64uA
0uA
0V
Vp=0.8V
1.6V
0.8V
0V
3V
2V
1V
Output of UVLO
POR
8
For a given start-up time, the soft-start capacitor
(nF) can be estimated as:
V
1
V
2
C
ss
start
)
1
--(
)
ms
(
T
A
22
C
start
SS
*
μ
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相關代理商/技術參數(shù)
參數(shù)描述
IR3638STRPBF 功能描述:電壓模式 PWM 控制器 HI FREQ SYNC PWM 400kHz 0.6V Track RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
IR3640MPBF 功能描述:IC REG CTRLR BUCK PWM VM 20-MLPQ RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR)
IR3640MTRPBF 功能描述:開關變換器、穩(wěn)壓器與控制器 HI FREQ SYNC PWM 4.5 to 5.5V 1.5MHz RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel
IR3651 制造商:IRF 制造商全稱:International Rectifier 功能描述:
IR3651SPBF 功能描述:IC REG CTRLR BUCK PWM VM 14-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標準包裝:4,000 系列:- PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1.5MHz 占空比:66.7% 電源電壓:4.75 V ~ 5.25 V 降壓:是 升壓:無 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 85°C 封裝/外殼:40-VFQFN 裸露焊盤 包裝:帶卷 (TR)
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