UPD17708 datasheet(263/356 Pages) NEC

부품명	UPD17708

상세설명	4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DEDICATED HARDWARE FOR DIGITAL TUNING SYSTEM

PDF	356 Pages

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제조업체	NEC [NEC]

홈페이지	http://www.nec.com/

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263 / 356 page

263

µPD17704, 17705, 17707, 17708, 17709

17.4.2 Function of phase comparator

As shown in Figure 17-7, the phase comparator compares the phases of the divided frequency “fN” output by the

programmable divider and the reference frequency “fr”, and outputs an up or down request signal.

If the divided frequency fN is lower than reference frequency fr, the up request signal is output. If fN is higher than

fr, the down request signal is output.

Figure 17-8 shows the relationship between reference frequency fr, divided frequency fN, up request signal, and

down request signal.

When the PLL frequency synthesizer is disabled, neither the up request nor the down request signal is output.

The up and down request signals are input to the charge pump and unlock FF, respectively.

Figure 17-8. Relationship between fr, fN, UP, and DW

(a) If fN lags behind fr

(b) If fN leads fr

(d) If fN is lower than fr

UPD17708 데이터시트(PDF) 263 Page - NEC