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| 型号： | A8739EEETR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 18/23页 |
| 文件大小： | 0K |
| 描述： | IC PHOTOFLASH CHARGER 8-DFN |
| 标准包装： | 1 |
| 应用： | 照相机闪光灯电容器充电器，Xenon |
| 电流 - 电源： | 2mA |
| 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： | 8-UFDFN 裸露焊盘 |
| 供应商设备封装： | 8-DFN（2x2） |
| 包装： | 标准包装 |
| 其它名称： | 620-1365-6 |
A8739
Ultra-Small Mobile Adjustable 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 10.
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 10. Transformer Selection Relationships
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
17
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| A8740EEETR-T | 功能描述:IC PHOTOFLASH CAP CHARGER 8DFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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| A874L | 功能描述:通用继电器 CONTACTOR 3 PST RoHS:否 制造商:Omron Electronics 触点形式:1 Form A (SPST-NO) 触点电流额定值:150 A 线圈电压:24 VDC 线圈电阻:144 Ohms 线圈电流:167 mA 切换电压:400 V 安装风格:Chassis 触点材料: |
| A-874L | 制造商:MA-COM 制造商全称:M/A-COM Technology Solutions, Inc. 功能描述:A-874L 3PST, 335 Amps, 200 VAC, 400 Hz |
| A874WA1 | 功能描述:通用继电器 RELAY RoHS:否 制造商:Omron Electronics 触点形式:1 Form A (SPST-NO) 触点电流额定值:150 A 线圈电压:24 VDC 线圈电阻:144 Ohms 线圈电流:167 mA 切换电压:400 V 安装风格:Chassis 触点材料: |
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