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High-Power Synchronous HBLED
Drivers with Rapid Current Pulsing
Synchronization
The MAX16821A/MAX16821B/MAX16821C synchronize
to an external clock connected to RT/SYNC. The appli-
cation of an external clock at RT/SYNC disables the
internal oscillator. Once the MAX16821A/MAX16821B/
MAX16821C are synchronized to an external clock, the
external clock cannot be removed if reliable operation
is to be maintained.
Control Loop
The MAX16821A/MAX16821B/MAX16821C use an
average current-mode control scheme to regulate the
output current (Figure 2). The main control loop con-
sists of an inner current regulation loop for controlling
the inductor current and an outer current regulation
loop for regulating the LED current. The inner current
regulation loop absorbs the double pole of the inductor
and output capacitor combination reducing the order of
the outer current regulation loop to that of a single-pole
system. The inner current regulation loop consists of a
current-sense resistor (R S ), a current-sense amplifier
(CSA), a current-error amplifier (CEA), an oscillator pro-
viding the carrier ramp, and a PWM comparator
(CPWM) (Figure 2). The MAX16821A/MAX16821B/
MAX16821C outer LED-current control loop consists of
a differential amplifier (DIFF), a reference voltage, and
a voltage-error amplifier (VEA).
Inductor Current-Sense Amplifier
The differential current-sense amplifier (CSA) provides a
34.5V/V DC gain. The typical input offset voltage of the
current-sense amplifier is 0.1mV with a 0 to 5.5V common-
mode voltage range (V IN = 7V to 28V). The current-sense
amplifier senses the voltage across R S . The maximum
common-mode voltage is 3.2V when V IN = 5V.
Inductor Peak-Current Comparator
The peak-current comparator provides a path for fast
cycle-by-cycle current limit during extreme fault condi-
tions, such as an inductor malfunction (Figure 3). Note
the average current-limit threshold of 27.5mV still limits
the output current during short-circuit conditions. To
prevent inductor saturation, select an inductor with a
saturation current specification greater than the aver-
age current limit. The 60mV threshold for triggering the
peak-current limit is twice the full-scale average cur-
rent-limit voltage threshold. The peak-current compara-
tor has only a 260ns delay.
R CF
C CP
R IN
R F
C F
C CZ
DIFF
EAN
EAOUT
CSN
CSP
CLP
CA
V IN
SENSE+
DIFF
VEA
CEA
CPWM
DRIVER
L
LED
STRING
SENSE-
C OUT
V REF
Figure 2. MAX16821A/MAX16821B/MAX16821C Control Loop
MODE = SGND
R S
R LS
10
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相关代理商/技术参数
MAX16821EVKIT+ 制造商:Maxim Integrated Products 功能描述:HIGH-POWER SYNCHRONOUS HBLED DRIVER - Boxed Product (Development Kits)
MAX16822AASA/V+ 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822AASA/V+T 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822AASA+ 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822AASA+T 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822BASA+ 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822BASA+T 功能描述:LED照明驱动器 2MHz HB w/MOSFET & HSide Crnt Sense 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
MAX16822BEVKIT+ 功能描述:LED 照明开发工具 MAX16822B Eval Kit RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: