NUC505-YO2Y datasheet(86/130 Pages) NUVOTON

86 / 130 page

NUC505

July. 26, 2018

Page 86 of 130

Rev.1.08

6.3.3

Clock Generator

The clock generator consists of 4 clock sources, which are listed below:



Real-time clock (RTC_CLK) source can be selected from external 32.768 kHz

external low speed crystal oscillator (LXT) or 32.768 kHz internal low speed RC

oscillator (LIRC)



12 MHz external high speed crystal oscillator (HXT)



Programmable System PLL output clock frequency (PLL_FOUT)



Programmable Audio PLL output clock frequency (APLL_FOUT)

XT1_OUT

External 12

MHz Crystal

(HXT)

HXTEN (CLK_PWRCTL[0])

XT1_IN

PLL

PLL_FOUT

X32_OUT

External 32.768

kHz Crystal

(LXT)

X32_IN

Internal 32.768

kHz Oscillator

(LIRC)

HXT

APLL

APLL_FOUT

RTC_CLK

LIRC

LXT

RTC_CLKSRC[0]

Figure 6.3-2 Clock Generator Block Diagram

The external crystal oscillator and two capacitors are connected to the

pad “XT1_IN / X32_IN” and pad

“XT1_OUT / X32_OUT”. The capacitance value of the two capacitors may be changed for differential

crystal oscillator from different vender. The load capacitance values and resistance values must be

adjusted according to the selected oscillator. The recommended load capacitance values and

resistance values as

Crystal Oscillator

Capacitance Values

Resistance Values

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