如何用VSR51L2070微控制器驱动5V 字符型LCD.pdf

VRS51L2070 AN502 – How to run a 5V LCD from a 3.3V MCU Rev # Running a 5V Character LCD Interface from a 3.3V MCU Abstract Generating a 5V LCD Supply This application note explains how to operate a 5 volt Traditional methods of providing supply to the LCD character LCD module in a 3.3 volt system based on module include: Ramtron’s VRS51L2070 Versa 8051 microcontroller. • Using a separate 5V linear or switching The character LCD module is a simple and inexpensive regulator for the LCD module. solution for system status displays or user interface displays. In a typical application, the character LCD • Drawing the 5V supply from the VRS51L2070 will be used in conjunction with a switch or numeric 3.3V supply using integrated an voltage keypad, for instance, in a home alarm system. doubler or a step-up switching regulator. The scope of this application note is to demonstrate These methods, however, are expensive, cumbersome how to interface a standard 5V character LCD module and inefficient in terms of board space, since the with the VRS51L2070 using only a 3.3V supply. It will current consumption of most character LCD modules is also address how to use the MCU’s Pulse Width only a few mA. Modulator (PWM) outputs to generate the LCD 5V The solution proposed in this document will take supply and bias voltage.