MB1503 Просмотр технического описания (PDF) - Fujitsu

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MB1503

LOW-POWER PLL FREQUENCY SYNTHESIZER WITH POWER SAVE FUNCTION (1.1GHz)

Fujitsu 

Phase comparator output waveform (FC = High)

MB1503

fR

fP

LD

H

DO

fR > fP

Z

fR = fP

L

fR < fP

fR < fP

fR < fP

Notes: 1. Phase difference detection range: –2π to +2π

2. Spike appearance depends on the charge pump characteristics. Also, the spike is output to diminish

dead band.

3. When fR > fP or fR < fP, a spike might not appear depending on the charge pump characteristics.

4. LD is low when the phase difference is tw or more. LD is high when the phase difference is tw or less for

three or more cycles (when fOSCIN = 12.8MHz, tw = 625 to 1,250ns).

Analog switch

The LE signal turns the analog switch on or off. When the analog switch is turned on, the charge pump output (DO) is output through

the BiSW pin. When it is turned off, the BiSW pin is in the high-impedance state.

When LE = high (when the divide ratio of the internal divider is changed): Analog switch = on

When LE = low (normal operating mode): Analog switch = off

The LPF time constant can be decreased by inserting an analog switch between LPF1 and LPF2. This decreases the lock-up time

when the PLL channel is changed.

CHP

DO

LPF–1

LPF–2

(Control signal LE)

Analog

switch

BiSW

VCO

9

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