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参数资料
| 型号： | A8437ECGLT |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 16/22页 |
| 文件大小： | 0K |
| 描述： | IC PHOTOFLASH CAP CHARGER WLCSP |
| 标准包装： | 24,000 |
| 应用： | 照相机闪光灯电容器充电器，Xenon |
| 电源电压： | 2.3 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 12-UFBGA，WLCSP |
| 供应商设备封装： | 12-WLCSP |
| 包装： | 带卷 (TR) |
A8437
Transformer Selection
Mobile Phone Xenon Photoflash Capacitor Charger
with IGBT Driver
The minimum pulse width for t off determines what
1. The transformer turns ratio, N, determines the out-
put voltage:
N = N S / N P
V OUT = 31.5 × N – V d ,
where 31.5 is the typical value of V OUTTRIP , and V d is
the forward drop of the output diode.
2. The primary inductance, L P , determines the on-time
of the switch:
t on = (– L P / R ) × ln (1 – I SWlim × R / V IN ) ,
where R is the total resistance in the primary current
path (including R SWDS(on) and the DC resistance of the
transformer).
If V IN is much larger than I SWlim × R, then t on can be
approximated by:
t on = I SWlim × L P / V IN .
3. The secondary inductance, L S , determines the off-
time of the switch. Given:
is the minimum L P required for the transformer. For
example, if I SWlim = 0.7 A, N = 10, and V OUT = 315 V,
then L P must be at least 9 μ H in order to keep t off at
200 ns or longer. These relationships are illustrated in
the figure at the bottom of the page.
In general, choosing a transformer with a larger L P
results in higher efficiency (because a larger L P means
lower switch frequency and hence lower switching
loss). But transformers with a larger L P also require
more windings and larger magnetic cores. Therefore, a
trade-off must be made between transformer size and
efficiency.
Component Selection
Selection of the flyback transformer should be based
on the peak current, according to the following table:
I Peak Range L P
L S / L P = N × N , then
t off = ( I SWlim / N ) × L S / V OUT
= ( I SWlim × L P × N ) / V OUT .
(A)
0.4 to 1.0
0.6 to 1.2
0.75 to 1.0
Supplier
TDK
TDK
TDK
Part Number
LDT565630T-002
LDT565630T-003
LDT565620ST-203
( μ H)
14.5
10.5
8.2
V SW
t on
t off
I SW
V IN
I SW
V r
t f
t neg
V IN
V SW
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
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| 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 |
| A8438_06 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Photoflash Capacitor Charger with IGBT Driver |
| A8438_13 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Photoflash Capacitor Charger with IGBT Driver |
| A8438EEJTR-T | 功能描述:IC PHOTOFLASH CHARGER 10-MLP RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 应用说明:Ultrasound Imaging Systems Application Note 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:37 系列:- 应用:医疗用超声波成像，声纳 电流 - 电源:- 电源电压:2.37 V ~ 6 V 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:56-WFQFN 裸露焊盘 供应商设备封装:56-TQFN-EP（8x8） 包装:管件 |
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