Datasheet

MinimizingI
CC
WhenI/OsControlLEDs
LED
LEDx
V
C
C
100 kW
V
C
C
LED
3.3 V
5 V
LEDx
V
C
C
PCA9554
www.ti.com ........................................................................................................................................................SCPS128B–JULY2006–REVISEDAUGUST2008
WhentheI/OsareusedtocontrolLEDs,theyarenormallyconnectedtoV
CC
througharesistorasshownin
Figure14.TheLEDactsasadiode,sowhentheLEDisoff,theI/OV
IN
isabout1.2VlessthanV
CC
.ΔI
CC
in
ElectricalCharacteristicsshowshowI
CC
increasesasV
IN
becomeslowerthanV
CC
.
Forbattery-poweredapplications,itisessentialthatthevoltageofI/OpinsisgreaterthanorequaltoV
CC
when
theLEDisofftominimizecurrentconsumption.Figure15showsahigh-valueresistorinparallelwiththeLED.
Figure16showsV
CC
lessthantheLEDsupplyvoltagebyatleast1.2V.BothofthesemethodsmaintaintheI/O
V
IN
atoraboveV
CC
andpreventadditionalsupply-currentconsumptionwhentheLEDisoff.
Figure15.High-ValueResistorinParallelWithLED
Figure16.DeviceSuppliedbyaLowerVoltage
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