Methods of Controlling Laser Drivers: POTs and DACs

Abstract:Alasermoduledesignercanuseafixedresistor,mechanicalpot,digitalpot,oradigital-to-analogconverter(DAC)tocontrolthelaserdriver'smodulationandbiascurrents.Theadvantagesofaprogrammablemethod(POTorDAC)arethatthemanufacturingprocesscanbeautomatedanddigitalcontrolcanbeapplied(e.g.,tocompensatefortemperature).UsingPOTscanbeamoresimpleapproachthanaDAC.TherecanbeaslightcostadvantagetousingaPOT,butthisisusuallynotsignificantrelativetootherpiecesofthedesign.UsingaDACcanofferadvantages,includingimprovedlinearity(translatingtoeaseofsoftwareimplementationandabilitytohittherequiredaccuracy),increasedboarddensity,awiderrangeofresolutions,abetteroptimizationrange,easeofusewithanegativevoltagelaserdriver,andunit-to-unitconsistency.Maxim>AppNotes>A/DandD/ACONVERSION/SAMPLINGCIRCUITSDIGITALPOTENTIOMETERSFIBER-OPTICCIRCUITSKeywords:laserdriver,pots,digitalpot,digipot,lasermodulation,digitalpotentiometers,lasermodulation,Mar26,2002DS1845,DS1848APPLICATIONNOTE1010MethodsofControllingLaserDrivers:POTsandDACsAbstract:Alasermoduledesignercanuseafixedresistor,mechanicalpot,digitalpot,oradigital-to-analogconverter(DAC)tocontrolthelaserdriver'smodulationandbiascurrents.Theadvantagesofaprogrammablemethod(POTorDAC)arethatthemanufacturingprocesscanbeautomatedanddigitalcontrolcanbeapplied(e.g.,tocompensatefortemperature).UsingPOTscanbeamoresimpleapproachthanaDAC.Therecanbeaslightcostadvantagetou