Motor de Búsqueda de Datasheet de Componentes Electrónicos
  Spanish  ▼
ALLDATASHEET.ES

X  

Preview PDF HTML

HT7939A Datasheet(PDF) 5 Page - Holtek Semiconductor Inc

No. de pieza HT7939A
Descripción Electrónicos  Performance White LED Driver
PDF  13 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricante Electrónico  HOLTEK [Holtek Semiconductor Inc]
Página de inicio  http://www.holtek.com
Logo HOLTEK - Holtek Semiconductor Inc

HT7939A Datasheet(HTML) 5 Page - Holtek Semiconductor Inc

  HT7939A Datasheet HTML 1Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 2Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 3Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 4Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 5Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 6Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 7Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 8Page - Holtek Semiconductor Inc HT7939A Datasheet HTML 9Page - Holtek Semiconductor Inc Next Button
Zoom Inzoom in Zoom Outzoom out
 5 / 13 page
background image
Rev. 1.00
5
April 19, 2012
HT7939A
Input and Output Capacitor Selection
Theoutputcapacitordeterminesthesteadystate
outputvoltageripple.Thevoltagerippleisrelated
tothecapacitor’scapacitanceanditsESRwhichis
theEquivalentSeriesResistance.Ceramiccapacitors
withlowESRvalueswillresultinthelowestripple
voltagevaluesandaretherecommendedtype.Due
totheirlowESRvalues,thecapacitancevaluecanbe
calculatedusingthefollowingequation:
ri ppl e
SW
OU T
OU T
IN
O
ou t
V
F
V
I
V
V
C
´
´
´
-
=
)
(
Intheequationabove,Vripple=peaktopeakoutput
ripple,FSWistheswitchingfrequency.
Theoutputcapacitorisrecommendedtobeinarange
of1μFto10μF.Theinputcapacitorisrequiredtobe
inarangeof2.2μFto10.0μF.Theoutputcapacitor
affectstheloopstabilityoftheboostregulator.Ifthe
outputcapacitorislowerthanthisrange,theboost
regulatorcouldpotentiallybecomeunstable.
Schottky Diode Selection
Theoutputrectifierdiodesuppliescurrenttothe
inductor whentheinternal MOSFETisoff.The
averageandpeakcurrentratingsofthediodemustbe
greaterthanthemaximumoutputcurrentandpeak
inductorcurrent.Thereversebreakdownvoltage
mustbegreaterthanthemaximumoutputvoltage.It
isrecommendedtouseaschottkydiodewithalow
forwardvoltagetominimisepowerdissipationand
thereforetomaximisetheefficiencyoftheconverter.
A1N5819diodetypeisrecommendedforHT7939A
applications.
LED Current Selection
TheLEDcurrentiscontrolledbythecurrentsense
feedbackresistorRfb,Thecurrentsensefeedback
referenceis200mV.InordertoensureaccurateLED
currents,precisionresistorswitha1%tolerancearethe
preferredtypes.TheLEDcurrentcanbecalculated
usingthefollowingformula:
fb
FB
LE D
fb
R
R
V
I
mV
20 0
=
=
WhereILEDistheoutputLEDcurrent,VFB=feedback
voltage,Rfb=currentsenseresistor.
Digital and Analog Dimming Control
TheDigitaldimmingmethodusesaPWMsignal
applied to the EN pin and the EN Pin dimming
frequencyupto200kHz.Thisisshowninfig.19.The
averageLEDcurrentincreasesproportionallywiththe
PWMsignaldutycycle.A0%dutycyclecorresponds
tozeroLEDcurrent.A100%dutycyclecorresponds
toafullLEDcurrent.
TherearetwomethodstocontroltheLEDbrightness
foranalogdimming.ThefirstmethodusesaDC
voltagetocontrolthefeedbackvoltage.IftheDC
voltagerangeisfrom0Vto3.3V,theselectionof
resistorsprovidedinfig.20controlstheLEDcurrent
from20mAto0mA.Otherapplicationsafiltered
PWMsignal,whichisshowninfig.21.Thefiltered
PWMsignalapplicationactsthesamewayastheDC
voltagedimmingcontrol.



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13


Datasheet Descarga

Go To PDF Page


Enlace URL



¿ALLDATASHEET es útil para Ud.?  [ DONATE ] 

Todo acerca de Alldatasheet   |   Publicidad   |   Contáctenos   |   Política de Privacidad   |   Enlace a la hoja de datos    |   Intercambio de Enlaces   |   Lista de Fabricantes
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com