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| 型号： | A8732EEETR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 17/21页 |
| 文件大小： | 0K |
| 描述： | IC PHOTOFLASH CAP CHARGER 8DFN |
| 标准包装： | 1 |
| 应用： | 照相机闪光灯电容器充电器，Xenon |
| 电流 - 电源： | 50µA |
| 电源电压： | 1.5 V ~ 5.5 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-UFDFN 裸露焊盘 |
| 供应商设备封装： | 8-DFN/MLP（2x2） |
| 包装： | 标准包装 |
| 其它名称： | 620-1338-6 |
A8732
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
Applications Information
Transformer Design
1. The transformer turns ratio, N, determines the output 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 for-
ward drop of the output diode.
2. The primary inductance, L PRIMARY , determines the on-time of
the switch:
t on = (– L PRIMARY / R ) × ln (1 – I SWlim × R / V IN ) ,
where R is the total resistance in the primary current path (includ-
ing 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 approxi-
mated by:
t on = I SWlim × L PRIMARY / V IN .
3. The secondary inductance, L SECONDARY , determines the off-
time of the switch. Given:
L SECONDARY / L PRIMARY = N × N , then
t off = ( I SWlim / N ) × L SECONDARY / V OUT
= ( I SWlim × L PRIMARY × N ) / V OUT .
t on
V SW
The minimum pulse width for t off determines what is the mini-
mum L PRIMARY required for the transformer. For example, if
ILIM8 = 1.0 A, N = 10, and V OUT = 315 V, then L PRIMARY must
be at least 6.3 μ H in order to keep t off at 200 ns or longer. These
relationships are illustrated in figure 8.
In general, choosing a transformer with a larger L PRIMARY results
in higher efficiency (because a larger L PRIMARY corresponds to
a lower switch frequency and hence lower switching loss). But
transformers with a larger L PRIMARY also require more windings
and larger magnetic cores. Therefore, a trade-off must be made
between transformer size and efficiency.
Leakage Inductance and Secondary Capacitance
The transformer design should minimize the leakage induc-
tance to ensure the turn-off voltage spike at the SW node does
not exceed the absolute maximum specification on the SW pin
(refer to the Absolute Maximum Ratings table). An achievable
minimum leakage inductance for this application, however, is
usually compromised by an increase in parasitic capacitance.
Furthermore, the transformer secondary capacitance should be
minimized. Any secondary capacitance is multiplied by N 2 when
reflected to the primary, leading to high initial current swings
when the switch turns on, and to reduced efficiency.
t off
I SW
V IN
I SW
V r
t f
V IN
V SW
t neg
Figure 8. Transformer Selection Relationships
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
16
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| A8733EEJTR-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 |
| A8735 | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger with IGBT Driver |
| A8735EEETR-T | 功能描述:IC PHOTOFLASH CAP CHARGER 8DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:50 系列:- 应用:热电冷却器 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:28-SOIC（0.173"，4.40mm 宽）裸露焊盘 供应商设备封装:28-TSSOP 裸露焊盘 包装:管件 产品目录页面:1410 (CN2011-ZH PDF) |
| A8737EEJTR-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:- 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 |
| A87386-000 | 制造商:TE Connectivity 功能描述:V2-2.5-5-SP-SM - Bulk |
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