使用TC682方案设计的执行负压倍增功能

CreatinganegativeDCbiasvoltagefromapositiveDC

supplyoftenisrequiredinbattery-powered,portable,

hand-heldinstrumentsthatuseaLiquidCrystalDisplay

(LCD).ManyLCDsrequirearelativelylargenegative

bias(ontheorderof-10V).Sincemanyportable

systems(suchascellularsubscriberunits)oftenhave

aregulated+5VDCbiasavailable,thecriticaldesign

taskinvolvesconvertingthissupplyvoltagetoa

negativeDCbiasfortheLCD.Thisapplicationnote

discussestheadvantagesanddisadvantagesof

severalalternativesforimplementingthe-10Vbias

requiredbytheLCD.MAN804DesignAlternativesToTheTC682ForPerformingInvertingVoltageDoublerFunctionsAuthor:PatMarescaTRADITIONALTC682MicrochipTechnologyInc.IMPLEMENTATIONFigure1showsacircuitimplementationusingINTRODUCTIONMicrochipTechnology'sTC682togeneratethe-10VLCDbiasfromaregulated+5Vinput.AssumingthataCreatinganegativeDCbiasvoltagefromapositiveDC