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| 型号： | A8436EEJTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC PHOTOFLASH CHARGER 10-MLP |
| 标准包装： | 1 |
| 应用： | 照相机闪光灯电容器充电器 |
| 电流 - 电源： | 1.3mA |
| 电源电压： | 3 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 供应商设备封装： | 10-TDFN/MLP（3x3） |
| 包装： | 标准包装 |
| 产品目录页面： | 1141 (CN2011-ZH PDF) |
| 其它名称： | 620-1098-6 |
A8436
Photoflash Capacitor Charger with IGBT Driver
Functional Description
Overview
The A8436 is a photoflash capacitor charger control IC with
adjustable input current limiting. It also integrates an IGBT
driver for strobe operation of the flash tube, dramatically saving
board space in comparison to discrete solutions for strobe flash
operation. The control logic is shown in the functional block
diagram.
The charging operation of the A8436 is started by a low-to-high
signal on the CHARGE pin, provided that V IN is above V UVLO
level. If CHARGE is already high before V IN reaches V UVLO ,
another low-to-high transition on the CHARGE pin is required
to start the charging. When a charging cycle is initiated, the
transformer primary side current, I Primary , ramps up linearly at a
rate determined by the combined effect of the battery voltage,
V BATT , and the primary side inductance, L Primary . When I Primary
reaches the current limit, I SWLIM , set by configuring the ILIM
pin, the internal MOSFET is turned off immediately, allowing the
energy to be pushed into the photoflash capacitor, C OUT , from the
secondary winding. The secondary side current drops linearly as
C OUT charges.
While the internal MOSFET switch is turned off, the output
Fast Charging and Timer Modes
The IC operates in the Fast Charging mode when the photoflash
capacitor, C OUT , is only partially discharged. In Fast Charging
mode, the converter operates near the discontinuous boundary,
and a sensing circuit tracks the fly-back voltage at the SW node.
As soon as this voltage swings below 1.2 V, the internal MOS-
FET switch is turned on again, starting the next charging cycle.
The IC operates in the Timer mode when beginning to charge a
completely discharged photoflash capacitor, usually when the out-
put voltage, V OUT , is less than approximately 10 to 20 V. Timer
mode is a fixed 18 μ s off-time control. One advantage of the
A8436 watchdog timer control scheme is that it limits the initial
current surge and thus acts as a “soft-start.” As shown in figure 3,
the timer mode only lasts a small fraction of a second (usually <
100 ms). It can be recognized by its lower initial input charging
current as a result of a lower duty cycle. As output voltage rises to
more than 10 to 20 V, the adaptive Fast Charging mode takes over
the control, raising the average input current level.
voltage, V OUT , is sensed by a resistor string, R 1 through R 3 , con-
nected between the anode of the output diode, D1, and ground.
This resistor string forms a voltage divider that feeds back to the
FB pin. The resistors must be sized to achieve a desired output
voltage level based on a typical value of 1.205 V at the FB pin.
As soon as V OUT reaches the desired value, the charging process
is terminated. The user may toggle the CHARGE pin to refresh
the photoflash capacitor.
Switch On-Time and Off-Time Control
The A8436 implements an adaptive on-time/off-time control. (For
Timer
Mode
I BATT(Avg)
Fast Charging Mode
circuit details, please refer to the the Control Logic block in the
simplified Functional Block Diagram on page 2.) On-time dura-
tion, t ON , is determined by input voltage, V IN , transformer primary
inductance, L Primary , and the set current limit, I SWLIM . Off-time
duration, t OFF , depends on the operating conditions during switch
off-time. The A8436 applies its two charging modes, Fast Charg-
ing mode and Timer mode, according to those conditions.
V OUT
Figure 3. Sequencing of Timer mode and Fast Charging mode (time
axis scale is 1 s per division)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1 . 508.853.5000; www.allegromicro.com
9
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相关代理商/技术参数 |
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| A8437 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Mobile Phone Xenon Photoflash Capacitor Charger |
| A84377-000 | 制造商:TE Connectivity 功能描述:TXR66SJ00-3616BI - Bulk |
| A8437ECGLT | 功能描述:IC PHOTOFLASH CAP CHARGER WLCSP RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| A8437EEJTR-T | 功能描述:IC PHOTOFLASH CAP CHARGER 10TDFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| A8438 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Photoflash Capacitor Charger with IGBT Driver |
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