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参数资料
| 型号： | IR3637ASTRPBF |
| 厂商： | International Rectifier |
| 文件页数： | 5/19页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 8-SOIC |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 660kHz |
| 占空比： | 76% |
| 电源电压： | 4.5 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | 0°C ~ 125°C |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 包装： | 标准包装 |
| 其它名称： | IR3637ASTRPBFDKR |
IR3637ASPbF
THEORY OF OPERATION
Soft-Start
The IR3637A has a programmable soft-start to control
the output voltage rise and limit the current surge at the
25uA
3V
start-up. To ensure correct start-up, the soft-start se-
quence initiates when the Vc and Vcc rise above their
threshold (3.3V and 4.2V respectively) and generates
the Power On Reset (POR) signal. Soft-start function
SS/SD
POR
64uA
Max
HDrv
operates by sourcing an internal current to charge an
external capacitor to about 3V. Initially, the soft-start func-
tion clamps the E/A’s output of the PWM converter and
disables the short circuit protection. During the power
up, the output starts at zero and voltage at Fb is below
Comp
0.8V
Fb
25K
25K
Error Amp
LDrv
0.4V. The feedback UVLO is disabled during this time
by injecting a current (64 μ A) into the Fb. This generates
a voltage about 1.6V (64 μ A × 25K) across the negative
0.4V
input of E/A and positive input of the feedback UVLO
comparator (see Figure 3).
The magnitude of this current is inversely proportional to
64uA × 25K=1.6V
When SS=0
Feeback
UVLO Comp
POR
the voltage at soft-start pin.
The 20 μ A current source starts to charge up the exter-
nal capacitor. In the mean time, the soft-start voltage
ramps up, the current flowing into Fb pin starts to de-
crease linearly and so does the voltage at the positive
pin of feedback UVLO comparator and the voltage nega-
tive input of E/A.
When the soft-start capacitor is around 1V, the current
flowing into the Fb pin is approximately 32 μ A. The volt-
age at the positive input of the E/A is approximately:
Figure 3 - Soft-start circuit for IR3637A.
The output start-up time is the time period when soft-
start capacitor voltage increases from 1V to 2V. The start-
up time will be dependent on the size of the external
soft-start capacitor. The start-up time can be estimated
by:
25 μ A × T START /C SS = 2V-1V
For a given start up time, the soft-start capacitor can be
estimated as:
C SS ? 25 μ A × T START /1V
32 μ A × 25K = 0.8V
The E/A will start to operate and the output voltage starts
Output of UVLO
POR
3V
to increase. As the soft-start capacitor voltage contin-
ues to go up, the current flowing into the Fb pin will keep
decreasing. Because the voltage at pin of E/A is regu-
lated to reference voltage 0.8V, the voltage at the Fb is:
V FB = 0.8-25K × (Injected Current)
Soft-Start
Voltage
Current flowing
into Fb pin
0V
64uA
0uA
? 2V
? 1V
The feedback voltage increases linearly as the injecting
current goes down. The injecting current drops to zero
when soft-start voltage is around 2V and the output volt-
age goes into steady state.
Voltage at negative input ? 1.6V
of Error Amp and Feedback
UVLO comparator
0.8V
0.8V
As shown in Figure 4, the positive pin of feedback UVLO
comparator is always higher than 0.4V, therefore, feed-
Voltage at Fb pin
0V
back UVLO is not functional during soft-start.
www.irf.com
Figure 4 - Theoretical operational waveforms
during soft-start.
5
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相关代理商/技术参数 |
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| IR3637SPBF | 功能描述:IC REG CTRLR BUCK PWM VM 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| IR3637STRPBF | 功能描述:开关变换器、稳压器与控制器 2 CH OR 2 PHASE SYNC PWM CNTRLR RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| IR3638 | 制造商:ONSEMI 制造商全称:ON Semiconductor 功能描述:High Frequency Synchronous |
| IR3638DR2G | 制造商:ON Semiconductor 功能描述: |
| IR3638SPBF | 制造商:IRF 制造商全称:International Rectifier 功能描述:HIGH FREQUENCY SYNCHRONOUS PWM BUCK CONTROLLER FOR TRACKING APPLIACTIONS |
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