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LDS8620
BLOCK DIAGRAM
Figure 2. LDS8620 Functional Block Diagram
BASIC OPERATION
At power-up, EN/SET pin should be logic LOW. The
LDS8620 starts operating in 1-x mode when EN/SET
pin is asserted logic high and at least one channel is
enabled. At 1-x mode, the output will be
approximately equal to the input supply voltage (less
any internal voltage losses). If the output voltage is
sufficient to regulate all LED currents, the device
remains in 1-x operating mode.
The low dropout PowerLite ? Current regulator
(PCR) performs well at input voltages up to 50 mV
above LED forward voltage significantly increasing
driver’s efficiency. The LDS8620 monitors voltage
drop Vd across PCR at every channel in ON state. If
this voltage falls below 50 mV (typical) at any one
channel, (channel with LED with highest forward
voltage), the Mode Control Block changes charge
pump mode to the next multiplication ratio.
Vd = V IN x M – V F – Rcp x Iout, where Rcp is a
Charge Pump Output Resistance at given mode, Iout
is sum of all LED currents, and M is a charge pump’
multiplication ratio.
If the input voltage is insufficient or falls to a level
where Vd ≤ 50 mV, and the regulated currents cannot
be maintained, the low dropout PowerLite ? Current
Regulator switches the charge pump into 1.5-x mode
(after a fixed delay time of about 800 μ s). In 1.5-x
mode, the charge pump’ output voltage is
approximately equal to 1.5 times the input supply
voltage (less any internal voltage losses).
This sequence repeats at every mode until driver
enters the 2-x mode.
If the device detects a sufficient input voltage is
present to drive all LED currents in 1-x mode, it will
change automatically back to 1-x mode. This only
applies for changing back to the 1-x mode. The
difference between the input voltage when exiting 1-x
mode and returning to 1-x mode is called the 1-x
mode transition hysteresis (about 600 mV).
LED Current Setting
The current in each of the LED is programmed
through the 1-wire EN/SET digital control input. By
pulsing this signal according to a IXYS 1-wire
protocol, a set of internal registers can be addressed
and written into allowing to configure each of LEDs
with the desired current. There are five registers: the
first is 2 bits long, while registers 2 – 4 are six bits
long, and the fifth is one bit long. The registers are
? 2009 IXYS Corp.
Characteristics subject to change without notice
7
Doc. No. 8620DS, Rev. N1.1
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相关代理商/技术参数
LDS8621-002-T2
功能描述:LED照明驱动器 200mA Dual Output Flash/Lamp 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
LDS8621002-T2-960
功能描述:IC LED DRIVER FLASH 16WQFN RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:PowerLite™ 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C
LDS8640-002-T3
功能描述:LED照明驱动器 400mA Dual Output Flash/Lamp Drvr
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功能描述:LED照明驱动器 400mA Dual Output Flash/Lamp 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
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