Creating a negative DC bias voltage from a positive DC
supply often is required in battery-powered, portable,
hand-held instruments that use a Liquid Crystal Display
(LCD). Many LCDs require a relatively large negative
bias (on the order of -10V). Since many portable
systems (such as cellular subscriber units) often have
a regulated +5V DC bias available, the critical design
task involves converting this supply voltage to a
negative DC bias for the LCD. This application note
discusses the advantages and disadvantages of
several alternatives for implementing the -10V bias
required by the LCD. M AN804
Design Alternatives To The TC682 For Performing
Inverting Voltage Doubler Functions
Author: Pat Maresca TRADITIONAL TC682
Microchip Technology Inc. IMPLEMENTATION
Figure 1 shows a circuit implementation using
INTRODUCTION Microchip Technology's TC682 to generate the -10V
LCD bias from a regulated +5V input. Assuming that a
Creating a negative DC bias voltage from a positive DC ……
