HT66F20 datasheet(55/298 Pages) HOLTEK

55 / 298 page

Rev. 1.90

�e��a�� 18� �01�

Rev. 1.90

�e��a�� 18� �01�

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit MCU with EEPROM

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit MCU with EEPROM

External 32.768kHz Crystal Oscillator – LXT

TheExternal32.768kHzCrystalSystemOscillatorisoneofthelowfrequencyoscillatorchoices,

whichisselectedviaconfigurationoption.Thisclocksourcehasafixedfrequencyof32.768kHz

andrequiresa32.768kHzcrystaltobeconnectedbetweenpinsXT1andXT2.Theexternalresistor

andcapacitorcomponentsconnectedtothe32.768kHzcrystalarenecessarytoprovideoscillation.

Forapplicationswhereprecisefrequenciesareessential,thesecomponentsmayberequiredto

providefrequencycompensationduetodifferentcrystalmanufacturingtolerances.Duringpower-up

thereisatimedelayassociatedwiththeLXToscillatorwaitingforittostart-up.

WhenthemicrocontrollerenterstheSLEEPorIDLEMode,thesystemclockisswitchedofftostop

microcontrolleractivityandtoconservepower.However,inmanymicrocontrollerapplications

itmaybenecessarytokeeptheinternaltimersoperationalevenwhenthemicrocontrollerisin

theSLEEPorIDLEMode.Todothis,anotherclock,independentofthesystemclock,mustbe

provided.

However,forsomecrystals,toensureoscillationandaccuratefrequencygeneration,itisnecessary

toaddtwosmallvalueexternalcapacitors,C1andC2.TheexactvaluesofC1andC2shouldbe

selectedinconsultationwiththecrystalorresonatormanufacturersspecification.Theexternal

parallelfeedbackresistor,Rp,isrequired.

SomeconfigurationoptionsdetermineiftheXT1/XT2pinsareusedfortheLXToscillatororasI/O

pins.

• IftheLXToscillatorisnotusedforanyclocksource,theXT1/XT2pinscanbeusedasnormal

I/Opins.

• IftheLXToscillatorisusedforanyclocksource,the32.768kHzcrystalshouldbeconnectedto

theXT1/XT2pins.

To i nt er nal

ci rc ui ts

In te rn al

O sci ll at or

Ci rc ui t

No te :1 . Rp , C 1 and C 2 ar e re qui r ed.

2. A lt hough not s how n pi ns h av e a

par as it ic c apac it an ce o f ar ound 7pF .

In te r nal R C

O sc illa to r

32. 76 8

kH z

XT 1

XT 2

External LXT Oscillator

LXT Oscillator C1 and C2 Values

Crystal Frequency

��.768kHz

10p�

Note: 1. C1 and C� val�es a�e fo� g�idance onl�.

�. RP=5MΩ~10MΩ is recommended.

32.768kHz Crystal Recommended Capacitor Values

HT66F20 Datasheet(PDF) 55 Page - Holtek Semiconductor Inc

HT66F20 Datasheet(HTML) 55 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL