Linear 公司的LT8500是具有12位分辨率和解0MHz级联串口的48路led PWM发生器,输入电压3V-5.5V,有48个单独的PWM输出,高达6.1kHz的PWM频率(PWMCK = 25MHz),主要用在大屏显示器LED背光,单色,多色和全色LED显示器,马大哈控制,工业控制,ATE和机器人.本文介绍了LT8500主要特性,方框图以及多种应用电路.

48-ChannEL LED PWM Generator with 12-Bit Resolution and 50MHz Cascadable Serial Interface

The LTR8500 is a pulse width modulation (PWM) generator with 48 independent channels. Each channel has an individually adjustable 12-bit (4096-step) PWM register and a 6-bit (64-step) ±50% correction register. All controls are programmable via a simple serial data interface. Three banks of 16-channels each can be configured such that they operate 120° out-of-phase with each other.

The LT8500 features two diagnostic information flags: synchronization error and open LED. The flags are sent, with additional state information, on the serial data interface during status read back. The 50MHz cascadable serial data interface includes buffering and skew-balancing, making the chip suitable for PWM intensive applications such as large screen LCD dynamic backlighting and mono-,multi- and full-color LED displays. The LT8500 is also ideally suited to control three LT3595A LED drivers.

LT8500主要特性:

3V to 5.5V Input Voltage

48 Independent PWM Outputs

TTL/CMOS Logic 50MHz Serial Data Interface

12-Bit (4096 Steps) PWM Width Resolution

6-Bit (64 Steps) PWM Correction (±50% of Programmed PWM Width)

Up to 6.1kHz PWM Frequency (PWMCK = 25MHz)

Phase-Shift Option Reduces Switching Noise

Directly Controls Three LT3595A 16-Channel LED Drivers

Diagnostic Information: Sync Error/Open LED Flags

56-Pin (5mm × 9mm × 0.75mm) QFN Package

LT8500应用:

Large Screen Display LED Backlighting

Mono-, Multi-, Full-Color LED Displays

LED Billboards and Signboards

Motor Control

Industrial Control

Automated Test Equipment

Robotics

图1.LT8500方框图

图2.LT8500串行接口拓扑图

图3.LT8500采用5引脚拓扑驱动LT3595A的菊花链框图

图4.LT8500采用4引脚拓扑驱动LT3595A的菊花链框图

图5.单个LT8500驱动电阻镇流的48个LED串电路图

图6.单个LT8500实现48个DAC通路图