Datasheet

MinimizingI
CC
WhenI/OIsUsedtoControlLEDs
Px
LED
100 kΩ
V
CC
V
CC
3.3 V
Px
LED
5 V
V
CC
TCA6408A
www.ti.com .............................................................................................................................................................SCPS192C–APRIL2009–REVISEDJULY2009
WhentheI/OsareusedtocontrolLEDs,normallytheyareconnectedtoV
CC
througharesistorasshownin
Figure14.TheLEDactsasadiodesowhentheLEDisoff,theI/OV
IN
isabout1.2VlessthanV
CC
.TheΔI
CC
parameterinElectricalCharacteristicsshowshowI
CC
increasesasV
IN
becomeslowerthanV
CC
.Designsthat
mustminimizecurrentconsumption,suchasbatterypowerapplications,shouldconsidermaintainingtheI/Opins
greaterthanorequaltoV
CC
whentheLEDisoff.
Figure15showsahigh-valueresistorinparallelwiththeLED.Figure16showsV
CC
lessthantheLEDsupply
voltagebyatleast1.2V.BothofthesemethodsmaintaintheI/OV
IN
atoraboveV
CC
andpreventadditional
supplycurrentconsumptionwhentheLEDisoff.
Figure15.High-ValueResistorinParallelWithLED
Figure16.DeviceSuppliedbyaLowVoltage
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