参数资料
型号: SP7685ER-L
厂商: Exar Corporation
文件页数: 5/12页
文件大小: 0K
描述: IC LED DRVR PWM DIMMING 10DFN
标准包装: 1
拓扑: PWM,降压(降压),升压(升压),切换式电容器(充电泵)
输出数: 1
内部驱动器:
类型 - 主要: 背光,闪灯/白光
类型 - 次要: 高亮度 LED(HBLED),白色 LED
频率: 2.4MHz
电源电压: 2.7 V ~ 5.5 V
安装类型: 表面贴装
封装/外壳: 10-VFDFN 裸露焊盘
供应商设备封装: 10-DFN(3x3)
包装: 散装
工作温度: -40°C ~ 85°C
其它名称: 1016-1406
THEORY OF OPERATION
In the Torch mode, (Flash = GND) the Flash
pin is set to logic low and the SP7685 FB pin
regulates to 50mV output:
V FB = 50mV (Torch Mode)
When in Flash mode, (Flash = V IN ), the FB
regulation voltage is set by the resistor R SET
connected between the R SET pin and S GND
and the equation:
V FB = R SET * 14 μ A / 5 (Flash Mode)
Where 14 μ A is an internal regulated
current and 5 is an internal factor used to
scale the V SET voltage to the V FB voltage.
Typical values of R SET are 140K Ω to
35K Ω for a range of V FB = 400mV to
100mV in Flash mode.
The output current is then set in either Flash
or Torch mode by the equation:
I OUT = V FB / R SENSE
tion circuitry turns off the output switches
to prevent damage to the device. If the
temperature drops back down below 135
degrees Celsius, the part automatically
recovers and executes a soft start cycle.
OVERVOLTAGE PROTECTION
The SP7685 has over voltage protec-
tion. If the output voltage rises above
the 5.5V threshold, the over voltage
protection shuts off all of the output
switches to prevent the output voltage
from rising further. When the output
decreases below 5.5V, the device re-
sumes normal operation.
OVERCURRENT PROTECTION
The over current protection circuitry moni-
tors the average current out of the V OUT
pin. If the average output current exceeds
approximately 1.6 Amps, then the
overcurrent protection circuitry shuts off
the output switches to protect the chip.
FLASH TIMEOUT PROTECTION
BRIGHTNESS CONTROL USING PWM
Due to the high currents typically available
in Flash mode, it is necessary to protect the
white LED from damage if left on too long.
The SP7685 has a timeout in Flash mode of
approximately 2.6 seconds after which it will
shut down operation. Operation will not
begin again in Flash mode until the Enable
pin or Flash pin have been set Low and then
High again.
OVERTEMPERATURE PROTECTION
When the temperature of the SP7685 rises
above 145 ? C, the overtemperature protec-
Dimming control can be achieved by ap-
plying a PWM control signal to the EN pin.
The brightness of the white LEDs is con-
trolled by increasing and decreasing the
duty cycle of the PWM signal. While the
operating frequency range of the PWM
control is from 60Hz to 700Hz, the recom-
mended maximum brightness frequency
range of the PWM signal is from 60Hz to
200Hz. A repetition rate of at least 60Hz is
required to prevent flicker.
Date: 6/20/06 Rev T
SP7685, 1.2A Buck/BoostCharge Pump LED Driver
5
? 2006 Sipex Corporation
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