M685 Datasheet Rev 0.4

Revised 16Nov2004

Integr a t ed Cir cui t S ystems , Inc . ● N e tw or kin g & C o mm un icat ion s ● www. icst.com ● te l (5 08 ) 85 2-5 4 0 0

M685

Integrated

Circuit

Systems, Inc.

Prelimina r y Inf o r m ation

The M685 is a dual SAW, selectable frequency VCSO

frequency source for low-jitter clock

generation. An integrated SAW (surface

acoustic wave) delay line implements the

high-Q VCO (voltage controlled oscillator)

function, which results in low output phase

noise and very low jitter. The M685-01 is available in

a range of center frequencies from 125 to 175 MHz.

The M685-02 provides 500 to 700 MHz. Guaranteed

minimum pull-range of

±120 ppm meets GbE

requirements. (It also fully satisfies

±50 ppm minimum

pull-range specification commonly required.) Industry-

standard Kvco (VCO Gain) provides full replacement

compatibility. The M685 is well suited for phase-locked

loop implementations, clock and data recovery circuits,

and other timing applications in telecom and optical

fiber networking systems (e.g., OC-48).

◆ Two integrated SAW devices and selectable output

frequency; supports multi-rate optical interfaces

◆ M685-01 output frequencies from 125 to 175 MHz

M685-02 output frequencies from 500 to 700 MHz

(Specify center frequencies at time of order)

◆ Industry-standard Kvco for full compatibility

◆ Low phase jitter 0.2ps rms typical for the M685-02

(50kHz to 80MHz)

◆ Differential 3.3V LVPECL output

◆ Single 3.3V power supply

◆ Small 5 x 7.5mm SMT (surface mount) package

Figure 1: Pin Assignment

Figure 2: Block Diagram

Sample of Available Output Frequencies

VCSO Center

Note 1: Specify VCSO center frequencies at time of order

Applications

155.5200, 167.3316

SONET/SDH, SONET/SDH FEC

156.2500, 161.1328

Gigabit Ethernet, GbE FEC

622.0800, 669.3266

SONET/SDH, SONET/SDH FEC

625.0000, 644.5313

Gigabit Ethernet, GbE FEC

Table 1: Sample of Available Output Frequencies

M680

(To p Vi ew)

M685

F_SEL

VIN

nFOUT

SAW Delay Line

Phase

Shifter

M680

VCSO

FOUT

SAW Delay Line

Phase

Shifter

VCSO

M685

M685 Dual SAW, Selectable Frequency VCSO