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参数资料
| 型号： | A8837EEJTR-T |
| 厂商： | Allegro Microsystems Inc |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC IGBT DRIVER PHOTOFLASH 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： | 1.5mA |
| 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： | 1142 (CN2011-ZH PDF) |
| 其它名称： | 620-1248-6 |
A8837
Photoflash Capacitor Charger with IGBT Driver
current starts to ramp up to the set I SWLIM . The I SWLIM setting
remains in effect as long as the CHARGE pin is high. To reset the
ILIM counter, pull the CHARGE pin low before clocking in the
new setting.
After the first start-up or an ILIM counter reset, each new current
limit can be set by sending a burst of pulses to the CHARGE pin.
The first rising edge starts the ILIM counter, and up to 8 rising
edges will be counted to set the I SWLIM level. The first pulse
width, t ILIM1(H) , must be at least 20 μ s long. Subsequent pulses
(up to 7 more) can be as short as 0.2 μ s. The last low-to-high
edge must arrive within 54 μ s from the first edge. The CHARGE
pin will stay high afterwards.
Figure 6 shows the last charging cycle, when the CHARGE pin is
forced low before charging has been completed.
The A8837 implements an adaptive off-time, t OFF , control. After
the switch is turned off, a sensing circuit tracks the flyback volt-
age at the SW node. A special dV/dt detection circuit is used to
allow minimum-voltage switching, even if the SW voltage does
not drop to zero volts. This enables fast-charging to start earlier
than previously possible, thereby reducing the overall charging
time. However, when the photoflash capacitor charger circuit
starts up at low output voltage, a timeout may be triggered to
limit the maximum switch off-time to 18 μ s.
V CHARGE
V SW
I SW
V CHARGE
V SW
I SW
V CHARGE
V SW
I SWLIM = 2.0 A
I SWLIM = 1.8 A
I SWLIM = 1.6 A
V CHARGE
I SW
V SW
I SW
Figure 6. Last charging cycle, when the CHARGE pin is forced low before
charging is complete.
V CHARGE
V SW
I SWLIM = 1.4 A
I SW
Figure 7. ILIM programming waveforms for various I SWLIM ; V IN =
3.3 V, V BAT = 2.0 V, V CHARGE 5 V/div, V SW 2 V/div, I SW 500 mA/div,
time scale 10 μ s/div.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
8
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