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參數(shù)資料
| 型號： | A8439EEJTR-T |
| 廠商： | Allegro MicroSystems, Inc. |
| 英文描述： | Photoflash Capacitor Charger with IGBT Driver and Refresh |
| 中文描述： | 照相閃光燈電容充電器與IGBT驅(qū)動器和刷新 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大小： | 537K |
| 代理商： | A8439EEJTR-T |
A8439-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Photoflash Capacitor Charger with IGBT Driver
A8439
7
Functional Description
Overview
The A8439 is a photoflash capacitor charger control IC with
adjustable input current limiting and automatic refresh. It also
integrates an IGBT driver for strobe operation of the flash tube,
dramatically saving board space in comparison to discrete solu-
tions for strobe flash operation. The control logic is shown in the
functional block diagram.
The charging operation of the A8439 is started by a low-to-high
signal on the CHARGE pin. The primary peak current is set by
input clock signals from the CHARGE pin. 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
, 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. The recharging cycle starts again, either after the
transformer flux is reset, or after a predetermined time period,
t
OFF(Max)
(18
μ
s), whichever occurs first.
While the internal MOSFET switch is turned off, the output
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 A8439 automatically starts a new charging
cycle when the internal voltage sensing circuit detects a 10 %
drop in the output voltage. Toggling the CHARGE pin can also
start a refresh operation.
Auto Refresh
The A8439 features autorefresh when the feedback resistor
network is connected at the output. Autorefresh initiates when
the output voltage drops to
≈
90 % of the set stop voltage of the
resistor network. The operation is shown in figure 3.
Input Current Limiting
The peak current limit can be adjusted to eight different levels,
from 270 mA to 1.4 A, by clocking the CHARGE pin. An internal
digital circuit decodes the input clock signals to a counter, which
sets the charging time. This flexible scheme allows the user
to operate the flash circuit according to different battery input
voltages. The battery life can be effectively extended by setting a
lower current limit at low battery voltages.
Figure 4 shows the ILIM clock timing scheme protocol. The
total ILIM setup time, t
ILIM(SU)
, denotes the time needed for the
decoder circuit to receive ILIM inputs and set I
SWLIM
, and has a
typical duration of 60
μ
s.
Figure 3. Autorefresh waveform of A8439. Feedback resistor
network is connected at the output.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| A843DSC | 制造商:Pentair Technical Products / Hoffman 功能描述:Enclosure, Junction Box, 8.00x4.00x2.75in, Flat Cover, NEMA 4, Mild Steel 制造商:Pentair Technical Products / Hoffman 功能描述:ENCLOSURE JUNCTION BOX STEEL GRAY 制造商:Pentair Technical Products / Hoffman 功能描述:ENCLOSURE, JUNCTION BOX, STEEL, GRAY 制造商:Hoffman Enclosures 功能描述:SCREW COVER DSC ENCLOSURE8 X 4 X 2.75 制造商:Pentair Technical Products / Hoffman 功能描述:ENCLOSURE, JUNCTION BOX, STEEL, GRAY, Enclosure Type:Junction Box, Enclosure Mat 制造商:Pentair Technical Products / Hoffman 功能描述:ENCLOSURE, JUNCTION BOX, STEEL, GRAY, Enclosure Type:Junction Box, Enclosure Material:Steel, Body Color:Grey, External Height - Imperial:8", External Height - Metric:203mm, External Width - Imperial:4", External Width - Metric:102mm , RoHS Compliant: Yes |
| A844 | 制造商:TE Connectivity 功能描述:- Bulk |
| A8447 | 制造商:ALLEGRO 制造商全稱:Allegro MicroSystems 功能描述:High Voltage Step Down Regulator |
| A8447SLJ-T | 制造商:Allegro MicroSystems LLC 功能描述:HIGH VOLTAGE STEP DOWN REGULATOR |
| A8447SLJTR-T | 功能描述:IC REG BUCK ADJ 3A 8SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 產(chǎn)品培訓(xùn)模塊:MIC23xxx HyperLight Load™ Regulators 標(biāo)準(zhǔn)包裝:5,000 系列:HyperLight Load® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.8V 輸入電壓:2.7 V ~ 5.5 V PWM 型:混合物 頻率 - 開關(guān):4MHz 電流 - 輸出:2A 同步整流器:是 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:8-VFDFN 裸露焊盤，8-MLF? 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-MLF?（2x2） 產(chǎn)品目錄頁面:1094 (CN2011-ZH PDF) 其它名稱:576-3303-2 |
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