ZMDI ZLED7022六路低噪音LED驱动方案
ZMDI公司的Zled7022是六路低噪音恒定频率电荷泵DC/DC转换器,可驱动六路LED,每路LED的电流从1.8mA到20mA可编程,并联工作时可驱动更大电流的LED, 工作电压2.8V-5.5V,关断模式电流小于2uA,主要用在手提设备的LED背光,手机,智能手机和PDA的LED照明,数码相框照明等.本文介绍了ZLED7022主要特性和`优势,方框图以及典型应用电路.
The ZLED7022, one of our ZLED family of LED control ICs, is a low-noise, constant-frequency charge pump DC/DC converter that can drive up to six LED channELs, providing a programmable constant current level ranging from 1.8mA to 20mA per LED channel. It can also drive higher current LEDs because its current sinks can operate in parallel. It enables white or other color LED applications that require uniform intensity and/or linear progressions in brightness. Capable of operating efficiently with DC voltage supplies ranging from 2.8V to 5.5V, it is ideal for small, battery-powered applications because very few external components are needed: typically one small-dimension 1μF capacitor across the C+ and C- pins and two small-dimension 2.2μF capaci-tors to GND from the VCC and Vout pins.
The ZLED7022’s Pulse Count Control (PCC) serial digi-tal input is used to enable/disable the LEDs and set the current level (14 settings using a nearly logarithmic scale to provide a linear brightness progression). This simple, high-speed interface allows efficient real-time management of LEDs via microcontrollers or control systems.
The ZLED7022’s features include integrated soft-start circuitry to protect against excessive in-rush current during power-on and a low-current shutdown mode that reduces quiescent current consumption to approximately 1μA (typical) by disconnecting the load from the input when the EN/SET pin is low for a specified time.
ZLED7022主要特性:
Low quiescent current in low-current shutdown mode: 1μA typical; <2μA maximum
Integrated thermal shutdown protection prevents damage by shutting down the ZLED7022 if the die junction temperature exceeds 160℃ (typical)
Fixed charge pump switching frequency: 1MHz (typ.)
Soft-start feature protects against excessive inrush current during power-on
ZLED7022优势:
Current matching accuracy: ±0.9% (typical)
One-pin on/off or brightness control for up to six LEDs via a simple PCC serial interface—no pulse-width modulation or additional control circuit needed
14 programmable current levels for achieving real-time control of effects such as LED fade-out or sudden changes in brightness
Low EMI and back-injected noise because the charge pump is not inductor-based
Very few external components needed for operation
Flexible design enables diverse LED applications: up to 20mA per channel
LED driver family concept with low-voltage four-channel LED driver ZLED7012
ZLED7022典型应用:
LED backlighting for portable devices
LED lighting for cell phones, smartphones. PDAs
Illumination of digital photo frames
Backlighting for GPS / navigation systems
Low voltage LED lighting fixtures
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General purpose low-voltage industrial and consumer applications
图1.ZLED7022方框图
图2.ZLED7022应用电路
图3.ZLED7022采用D4:D0的基本应用电路
