Linear 公司的LT3593是降压DC/DC转换器，用单节3V锂电池可驱动多达10个串联的白光LED，并具有.32:1的线性亮度控制范围，可广泛应用在手机，数码相机，PDA，手提计算机，MP3播放器和GPS接收器.本文介绍了LT3593的主要性能，方框图以及驱动不同数量LED的应用电路图.

      The LT3593 is a step-up DC/DC converter designed to drive up to ten white LEDs in series from a Li-Ion cell.

      Series connection of the LEDs provides identical LED currents and eliminates the need for ballast resistors. The device features a unique high side LED current sense that enables the part to function as a “one wire current source” where the low side of the LED string can be returned to ground anywhere.

      Additional features include output disconnect in shutdown， open LED protection and 1-pin shutdown/LED current control. The CTRL pin is toggled to adjust the LED current via an internal counter and a 5-bit DAC.

      The LT3593 switches at 1MHz， allowing the use of tiny external components. Constant frequency switching results in low input noise and a small output capacitor. The LT3593 is available in the 6-lead DFN (2mmX2mm) as well as the 6-lead SOT-23 packages.

主要特性:
Drives Up to Ten White LEDs from a 3V Supply
One Pin Shutdown and Current Programming
LEDs Disconnected in Shutdown
32:1 Linear Brightness Control Range
VIN Range: 2.7V to 5.5V
±5% Output Current Accuracy at Full Scale
Low Shutdown Current: 3μA
1MHz Switching Frequency
Requires Only 1μF Output Capacitor
Low Profi le 6-Lead DFN (2mmX2mmX0.75mm) and 6-Lead SOT-23 Packages

应用:
Cell Phones
Digital Cameras
PDAs， Handheld Computers
MP3 Players
GPS Receivers

图1. LT3593方框图

图2. 锂电池驱动10个白光LED电路图

图3. 两节AA电池驱动3个白光LED电路图

图4. 锂电池驱动单个白光LED电路图

图5. 锂电池驱动两个白光LED电路图

图6. 锂电池驱动3个白光LED电路图

图7. 锂电池驱动4个白光LED电路图

图8. 锂电池驱动6个白光LED电路图

(from 中电网）