采用PWM和R-2R阶梯产生正弦波和DTMF波形DA转换器

Manyembeddedapplicationsrequirethegenerationof

analogsignals.AlthoughseparateD/AconverterIC’s

existonthemarkettoday,theirextrapricemakesthem

prohibitiveincostsensitiveembeddedcontroldesigns.

ThefollowingapplicationnotedescribestwoDAC

designsforgenerationofcomplexanalogwaveforms.:

(PWMandR-2RLadder).BoththePulseWidthModu-

lation(PWM)andresistorladdersrequireonlyafew

externalcomponentstocreateaD/Aconverterwiththe

PICmicro™microcontrollerseries.

Thesetechniquescanbeusedtogeneratedual-tone

multiplexedfrequencies(DTMF)fortelephonedialing,

controllingthespeedofamotor,generatingsoundand

complexwaveforms,andgeneratingvariablevoltages

inapowersupply.AN655D/AConversionUsingPWMandR-2RLadderstoGenerateSineandDTMFWaveformsoneapplicationtoanother.ThedesignershouldAuthors:RobSteinandJohnDayexperimentwiththisvaluetondthemostoptimalnum-MicrochipTechnologyInc.berfortheapplication.Thesetwocriteria(sinefre-quencyand#ofsteps)leadtotherequiredPWMfrequency:INTRODUCTIONPWM_Freq=(Sine_freq)(#ofsteps)10