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Low-Cost, 6-String WLED Drivers with
Quick-PWM Step-Up Converter
Figure 5 shows possible supply connection configura-
tions for the devices. The V CC pin should be bypassed
to GND with a minimum 1 F F ceramic capacitor.
Startup
At startup, the devices perform an LED check by pull-
ing up each FB_ pin with a current source to determine
whether a string of LEDs are connected. If an FB_ pin
is not connected with LEDs, it is disabled. The process
takes approximately 1ms. Then the current sources are
turned on.
Shutdown
The devices can be placed into shutdown by pulling the
EN pin low; when in shutdown mode, the current con-
sumption is 5 F A max. In the devices, the V CC voltage
drops to 0V with EN low.
Overvoltage Protection
To protect the step-up regulator when the load is open,
or the output voltage becomes excessive for any rea-
son, the devices feature a dedicated overvoltage feed-
back input by monitoring output (OVP). There are two
thresholds for OVP and they provide careful protections.
When the OVP voltage exceeds the 43V (typ) for the
MAX17129 or 25.4V for the MAX17149, an overvoltage
flag is set to enable the open-string detection. When
the OVP voltage exceeds 45.2V (typ), the internal power
MOSFET stops switching. This step-up regulator switch
is reenabled after the V OVP drops 1.8V (typ hysteresis)
below the protection threshold. This overvoltage protec-
tion feature ensures the step-up regulator fail-safe opera-
tion when the LED strings are disconnected from the
output. Considering overvoltage threshold and minimum
output regulation voltage, the MAX17149 is suitable for
3–6 LEDs per string and the MAX17129 is suitable for
6–11 LEDs per string.
LX
Overcurrent Protection
When in overcurrent condition, the devices latch off after
a fault timer expires. If running at full brightness, the
timeout is approximately 0.8ms (typ). If dimming, this
timeout is dependent on the dimming frequency and
duty cycle: the sum of the on-time cycles, during which
the device is in overcurrent condition, must be 0.8ms
(typ) for the timeout to expire.
LED Current Sources
Maintaining uniform LED brightness and dimming capa-
bility is critical for backlight applications. The ICs are
equipped with a bank of six matched current sources.
These specialized current sources are accurate within
Q 3% and match with each other within 2%. The LED
full-scale current is set through the ISET pin (10mA <
I LED_FS < 45mA).
The minimum voltage drop across each current source
is 275mV (typ) when the LED current is 20mA. The low-
voltage drop helps reduce dissipation while maintaining
sufficient compliance to control the LED current within
the required tolerances.
The LED current sources can be disabled by connecting
the respective FB_ pin to GND before startup. When the
devices are enabled, the controller scans settings for
all FB_ pins. If a FB_ pin is not tied to GND, an internal
circuit pulls this pin high, and the controller enables the
corresponding current source to regulate the string cur-
rent. If the FB_ pin is tied to GND, the controller disables
the corresponding current regulator. The current regula-
tor cannot be disabled by connecting the respective FB_
pin to GND after the IC is enabled.
All FB_ pins in use are combined to extract a lowest FB_
voltage (LVC) (see Figure 2). LVC is fed into the step-up
regulator’s error amplifier and is used to set the output
voltage.
LX
V IN
6V TO 26V
IN
IN
V CC
MAX17129
MAX17149
V S
3.0V TO 5.5V
V CC
MAX17129
MAX17149
Figure 5. Supply Configurations for the MAX17129/MAX17149
15
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相关代理商/技术参数
MAX17149ETE+T 功能描述:LED照明驱动器 6 WLED Driver with Quick-PWM 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
MAX1714AEEP 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
MAX1714AEEP+ 功能描述:电流型 PWM 控制器 Step-Down Controller for Notebook RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
MAX1714AEEP+T 功能描述:电流型 PWM 控制器 Step-Down Controller for Notebook RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
MAX1714AEEP-T 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
MAX1714AEEP-TG068 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述:
MAX1714AEVKIT 功能描述:电流型 PWM 控制器 Evaluation Kit for the MAX1714A RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14
MAX1714BEEE 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14