ZMDI ZLED7022六路低噪音LED驅動方案
ZMDI公司的Zled7022是六路低噪音恒定頻率電荷泵DC/DC轉換器,可驅動六路LED,每路LED的電流從1.8mA到20mA可編程,并聯工作時可驅動更大電流的LED, 工作電壓2.8V-5.5V,關斷模式電流小于2uA,主要用在手提設備的LED背光,手機,智能手機和PDA的LED照明,數碼相框照明等.本文介紹了ZLED7022主要特性和`優勢,方框圖以及典型應用電路.



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優勢:



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典型應用:



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





圖1.ZLED7022方框圖



圖2.ZLED7022應用電路



圖3.ZLED7022采用D4:D0的基本應用電路