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| 型号： | SP6887EB |
| 厂商： | Exar Corporation |
| 文件页数： | 9/10页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD FOR SP6887 |
| 标准包装： | 1 |
| 系列： | * |
THEORY OF OPERATION
Method 4: LED Current Setting Using
a PWM Signal to EN Pin
The 4 LEDs turn on and off by applying a
PWM signal to the EN pin as shown in
figure 3. The circuit is the same as to the
method 3, using a resistor RSET to set the
on state current and the average LED
current is then proportional to the
percentage of on-time when the EN pin is
logic low. Average LED current is
approximately equal to:
I LEDAVG = (t ON *I LED_ON )/ (t ON + t OFF )
Similarly, the recommended PWM
frequency is between 100Hz and 1KHz.
Due to start up delay and ramp up time,
frequency >1KHz will result in error in the
average value of ILED. Frequency <100Hz
can naturally cause the LEDs to blink
visibly.
Figure 3: PWM Signal at EN Pin for LED
Current Control
PCB Layout
When the driver is in the 1.5X charge
pump mode, the 1MHz switching
frequency operation require to minimize
the trace length and impedance to ground
on all 4 capacitors. A ground plane should
cover the area on the bottom side of the
PCB opposite to the IC and the bypass
capacitors. Capacitors CIN and Co require
to short connection to ground which can
be done with multiple vias as shown on
Figure4.
Square copper area matches the QFN 16
exposed pad (GND) which is connected by
a trace to the pin 12 pad (GND). A large
via (metalized hole) centered in the
square pad provides a low impedance
connection to the ground plane on the
opposite side of the PCB and allows the
heat dissipated by the driver IC to spread
out resulting in excellent thermal
performance.
Figure 4: PCB Lay-out
Rev. C – 10/31/2007
SP6887 4 Channel WLED Driver
9/10
? 2007 Exar Corporation
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相关代理商/技术参数 |
参数描述 |
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| SP6887ER4-L | 功能描述:LED照明驱动器 2.7V-5.5V 30mA temp -40C to 85C RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| SP6887ER4-L/TR | 功能描述:LED照明驱动器 4-CH REGULATED WITH WHITE LED DRVR RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| SP688-C | 功能描述:以太网和电信连接器 TX-6 PLUS MODULAR PLUG RoHS:否 制造商:Pulse 产品:Modular Jacks 性能类别: USOC 代码:RJ45 位置/触点数量: 安装风格:Through Hole 端口数量:1 x 1 型式:Female 屏蔽: 电流额定值: 电压额定值: 触点电镀: 外壳材料:Thermoplastic IP 等级: |
| SP689 | 制造商:SYNC-POWER 制造商全称:SYNC-POWER 功能描述:Ultra High Voltage Start Up |
| SP689S25RGB | 制造商:SYNC-POWER 制造商全称:SYNC-POWER 功能描述:Ultra High Voltage Start Up |
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