Detailed Description
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R S = ?
The MSL2041 and MSL2042 are highly integrated,
flexible, four-string LED drivers that use external
MOSFETs to allow high string currents, and include
power supply control to maximize efficiency of up
to two external string power supplies. Optimized for
stand-alone operation they require only external PWM
signal(s), a few external components (including the
string drive N-Channel MOSFETs) and an external string
power supply. The MSL2041/2s four MOSFET gate
drive outputs, G0 - G3, are optimized to drive FETs with
a maximum gate voltage threshold of 3V.
The MSL2041/2 LED drivers provide simple control
of LED brightness through both peak current and
external PWM drive controls. Peak current control, set
by external FET source resisters, offers excellent color
consistency, while pulse width control allows simple
brightness management. Multiple devices easily connect
together to drive more than four LED strings while
maintaining optimum system efficiency. An active low
fault output activates when either a string open circuit
or an LED short circuit condition is detected and verified.
The MSL2041/2 are intended for stand-alone operation
but offer additional string control and monitoring through
a 1MHz I 2 C/SMBus compatible serial interface. Use of
the serial interface is not required for operation.
The MSL2041 offers four PWM inputs that directly
control the four string drive outputs, while the MSL2042
requires only a single PWM input signal and features
automatic, progressive phase spreading of the four
string drive signals. With phase spreading a ? PWM
frame time delay is calculated and applied progressively
to the string drive signals. Phase spreading helps reduce
both the transient load on the LED power supply, and
the power supply output capacitor size requirement.
The Adaptive SourcePower Efficiency Optimizer (EO)
outputs control a wide range of different architectures of
external DC/DC and AC/DC converters. Multiple drivers
in a system communicate with each other in real time to
select an optimized operating voltage for the LEDs. The
EO allows design of the power supply for the worst case
Forward Voltage (V f ) of the LEDs without worrying
about excessive power dissipation issues, while ensuring
that the LED drive system is operating at optimum
12
efficiency. During start-up the EO automatically reduces
the string power supply voltage to the minimum value
required to keep the LEDs in current regulation. The EO
periodically performs re-optimization to compensate for
changes of the LED’s forward voltage, and to assure
continued optimum power savings. Additionally, all string
drivers are continually monitored for proper operation,
and if any of the LED strings become starved for current
the Efficiency Optimizer automatically increases the
string power supply voltage to bring the string back in
to current regulation.
Setting the Maximum LED String Current with
the FET Source Resistor R S
The maximum string current, I LED , for each string
is set by a shunt resistor, R S , connected to ground
from the source terminal of the string drive MOSFET
(Figure 1, page 6). Determine the resistor value using
? 127 ? ? 0.50196 ?
? 255 ? ? I LED ?
(where 127 is the default value of ISTR, String Current
Control register 0x0E). For example, a full-scale LED
current of 350mA returns R S = 0.715 Ω (to the nearest
1% resistor value).
LED String Fault Response
The MSL2041/2 monitor the LED strings to detect LED
short-circuit and string open-circuit faults (Figure 3).
When verified, all string faults force the open drain fault
output FLTB low.
After power-up, when shorted LEDs are verified in a
string the string is disabled and no longer monitored
by the Efficiency Optimizer. The short circuit threshold
is 6V (typical) and the additive voltage drop lost from
the shorted LEDs, plus the headroom required for the
external FET, must be equal to or greater than the 6V
threshold to generate a fault. Typically, two LEDs in a
string must be shorted to cause a short circuit fault,
Atmel LED Drivers-MSL2041/2042
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相关代理商/技术参数
MSL2041GU-R 功能描述:LED照明驱动器 Low-Cost, Simple 4-String LED Drivers 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
MSL2042 制造商:ATMEL 制造商全称:ATMEL Corporation 功能描述:Low-cost, Simple 4-string LED Drivers with External Current Sink MOSFETs, 5000:1 Dimming Range and Per String PWM Input
MSL2042GU 功能描述:LED照明驱动器 4Str RGB or White LED Driver lighting 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
MSL2042GU-R 功能描述:LED照明驱动器 4Str RGB or White LED Driver lighting 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
MSL-204AUYL-4 制造商:Unity Microelectronics Inc 功能描述:LED Uni-Color Amber 592nm 4-Pin SMD T/R
MSL-204B 制造商:UOT 制造商全称:Unity Opto Technology 功能描述:ALLEDs
MSL-204DR 制造商:UOT 制造商全称:Unity Opto Technology 功能描述:ALLEDs
MSL-204HW 制造商:UOT 制造商全称:Unity Opto Technology 功能描述:ALLEDs