Maxim 公司的MAX17061A是高效8串白光LED驱动器,适用于大型LCD显示器. MAX17061A内部集成了驱动LED阵列的开关电流模式升压控制器,该阵列可配置成并联8串LED,每串10个LED.每串的电流精度为±1.5%,从而保证了LED亮度的均匀性. MAX17061A的工作电压从7.5V到26V,固定电流25mA或可调整的从15mA到30mA,广泛用在笔记本电脑, 平板电脑(Tablet Computer)显示器,汽车电子系统和手持终端.本文介绍了MAX17061A的主要特性, 典型工作电路, 控制电路方框图以及PWM和SMBus接口电路.
8-String White LED Driver with SMBus for LCD Panel Applications
The MAX17061A is a high-efficiency driver for white lightemitting diodes (LEDs). It is designed for large liquidcrystal displays (LCDs) that employ an array of LEDs as the light source. An internal switch current-mode step-up controller drives the LED array, which can be configured for up to eight strings in parallel and 10 LEDs per string.
Each string is terminated with ballast that achieves ±1.5% current-regulation accuracy between strings, ensuring even LED brightness. The MAX17061A has a wide input voltage range from 7.5V to 26V, and provides a fixed 25mA or adjustable 15mA to 30mA full-scale LED current.
The MAX17061A internally generates a DPWM signal for accurate WLED dimming control. The DPWM frequency is resistor programmable, while DPWM duty cycle is controlled directly from an external PWM signal or through a control word through the MAX17061A’s SMBus interface.
This DPWM control provides a dimming range with 8-bit resolution and supports Intel display-power-saving technology (DPST) to maximize battery life.
The MAX17061A has multiple features to protect the controller from fault conditions. Separate feedback loops limit the output voltage under any circumstance, ensuring safe operation. Once an open string is detected, the string is disabled while other strings operate normally. The MAX17061A also features short LED detection. The shorted strings are also disabled after a 2ms fault blanking interval. The controller features cycle-by-cycle current limit to provide stable operation and soft-start capability. If the MAX17061A is in currentlimit condition, the step-up converter is latched off after an internal timer expires. A thermal-shutdown circuit provides another level of protection.
The MAX17061A’s step-up controller features an internal 150m (typ), 45V (max) power MOSFET with local current-sense amplifier for accurate cycle-by-cycle current limit. This architecture greatly simplifies the external circuitry and saves PCB space. Low-feedback voltage at each LED string 625mV (typ) at 25mA LED current helps reduce power loss and improve efficiency. The MAX17061A features selectable switching frequency (500kHz, 750kHz, or 1MHz), which enables a wide variety of applications that can trade off component size for operating frequency.
The MAX17061A is available in a thermally enhanced 28-pin, 4mm x 4mm Thin QFN package.
MAX17061A主要特性:
Accurate Dimming Control Using SMBus, PWM Interface
Dimming Range with 8-Bit Resolution
Adjustable DPWM Frequency with 1.5% Accuracy
Up to Eight Parallel Strings Multiple Series-Connected LEDs
±1.5% Current Regulation Accuracy Between Strings
Low String Feedback Voltage: 625mV at 25mA LED Current
Full-Scale LED Current Adjustable from 15mA to 30mA, or Preset 25mA
Open and Short LED Protections
Output Overvoltage Protection
0.15 Internal HV Power MOSFET (45V max)
Wide Input-Voltage Range from 4.5V to 26V
500kHz/750kHz/1MHz Selectable Switching Frequency
Small 28-Pin, 4mm x 4mm, Thin QFN package
MAX17061A应用:
Notebook, Subnotebook, and Tablet Computer Displays
Automotive Systems
Handy Terminals
