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| 型号： | A4401KL-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 5/17页 |
| 文件大小： | 0K |
| 描述： | IC QUASI FLYBACK CONVERTER 8SOIC |
| 标准包装： | 98 |
| 显示器类型： | 真空荧光 (VF) |
| 电流 - 电源： | 2.3mA |
| 电源电压： | 7 V ~ 40 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOICN |
| 包装： | 管件 |
A4401
Automotive Quasi-Resonant Flyback Control IC
Functional Description
Basic Operation
A peak current-mode control scheme is used to regu-
late one of the converter outputs, which will typically
be the highest output voltage. The regulated output
voltage is potentially divided down and fed into a
Gm stage, where the resulting error signal acts as the
control reference. This reference signal is compared
against the signal that is produced by the inductor
magnetization current flowing through the sense resis-
tor.
As shown in figure 1, at the beginning of a switching
cycle, the external MOSFET, Q1, is turned on. After
the sense resistor signal reaches the control reference
amplitude, the PWM comparator resets the synchronous
rectification (SR) latch and turns off the MOSFET.
When the MOSFET is turned off, the voltage on the
LX node rises until the voltage clamps at the bat-
tery voltage, V BAT , plus the reflected output voltage,
V OUT(RFL) . The secondary rectification diodes are
forward biased and the energy stored in the coupled
inductor is released to the output circuits. During this
period, the current through the inductor decreases lin-
early. As the current falls to 0 A, a resonance is set up
between the primary magnetizing inductance and any
capacitance appearing between the drain and ground.
A damped voltage ringing occurs, which resonates
around the battery voltage, V BAT . As the resonant ring
swings negative, the adaptive turn-on circuit moni-
tors to detect the point at which the voltage reaches a
minimum. At this point the MOSFET is commanded
on, thereby minimizing the turn-on losses. Also, the
relatively slow resonant dV/dt helps to reduce EMI.
In most applications, the converter will be operated
with a battery input voltage of 13.5 V. To optimize
the performance of the regulator at this voltage, the
magnetics can be designed to force 0 V across the
MOSFET at turn-on. This minimizes switching losses
and perhaps more importantly reduces EMI caused by
voltage ringing due to the drain to ground capacitor
resonating with the primary inductance. The voltage
resonance at the MOSFET turn-off can be reduced by
a simple low-loss R-C snubber, as described in the
Electromagnetic Interference section.
If a small enough load is applied to the outputs, and
the output of the Gm stage falls below a certain level,
+V
V BAT
Coupled inductor goes discontinuous;
resonant ring occurs
V OUT(RFL)
V OUT(RFL)
the converter will enter a burst mode of operation.
Burst mode reduces switching losses while maintain-
ing regulation of the outputs.
During startup, assuming the battery voltage is above
the turn-on threshold and the EN input is enabled, the
0
+I
MOSFET
turns off
MOSFET
turns on
controller turns on. A soft start circuit controls the ref-
erence voltage, limiting the amount of current drawn
on the input and the amount of charge transferred to
the output, preventing voltage overshoot. During the
initial phase of the soft start, very little or no voltage is
present on the output. This means that there will be no
Current released from
coupled inductor into
output circuit
? resonant
period
Current builds up in
primary winding of
coupled inductor
resonant phase and the converter will operate in con-
tinuous-conduction mode. The converter effectively
operates in constant-current mode until regulation is
Figure 1. External MOSFET voltage and current
achieved.
Allegro MicroSystems, LLC
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5
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相关代理商/技术参数 |
参数描述 |
|---|---|
| A4401KLTR-T | 功能描述:IC QUASI FLYBACK CONVERTER 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - 显示器驱动器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 显示器类型:真空荧光 (VF) 配置:5 x 7（矩阵） 接口:串行 数字或字符:- 电流 - 电源:3.5mA 电源电压:2.7 V ~ 3.6 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:16-SSOP（0.154"，3.90mm 宽） 供应商设备封装:16-QSOP 包装:带卷 (TR) |
| A4402 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Constant On-Time Buck Converter with Integrated Linear Regulator |
| A4402_1 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Constant On-Time Buck Converter with Integrated Linear Regulator |
| A4402_12 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:The A4402 is a dual-output regulator, combining in a single package a constant on-time buck regulator and a linear regulator (LDO)a??each with adjustable output voltages. |
| A4402ELPTR-T | 功能描述:IC REG DL BUCK/LINEAR 16-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 线性 + 切换式 系列:- 标准包装:2,500 系列:- 拓扑:降压（降压）同步（3），线性（LDO）（2） 功能:任何功能 输出数:5 频率 - 开关:300kHz 电压/电流 - 输出 1:控制器 电压/电流 - 输出 2:控制器 电压/电流 - 输出 3:控制器 带 LED 驱动器:无 带监控器:无 带序列发生器:是 电源电压:5.6 V ~ 24 V 工作温度:-40°C ~ 85°C 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* |
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