Preliminary

PLL650-04

Low EMI Clock for 10/100 PHY and Gigabit Ethernet

47745 Fremont Blvd., Fremont, California 94538 Tel (510) 492-0990 Fax (510) 492-0991 www.phaselink.com Rev 05/31/05 Page 2

PIN DESCRIPTIONS

Name

Number

Type

Description

XIN

1

I

Crystal input to be connected to a 25MHz fundamental parallel mode

XOUT/SSTE

2

B

Crystal connector. At power-up, the SSTE value that enables/disables the

spread spectrum function is latched in. 120k

Ω internal pull up resistor.

GND

3,11,15,17

P

Ground.

VDD

4,6,20

P

3.3V power supply.

CLKOUT_EN

5

I

CLKOUT enable pin. Disables CLKOUT to tri-state if ‘low’ (logical 0).

Internal 60k

Ω pull-up resistor defaults it to ‘high’ (logical 1).

CLKOUT

7,8,10,12,14

O

CLKOUT outputs with selectable frequency through FS(0:1). CLKOUT can

be modulated using SST to reduce EMI through SSTE. CLKOUT can be

disabled to tri-state with CLKOUT_EN.

FS0

13

TL

Tri-level frequency selector pin (See selection table on p.1). 0: connected

to GND, 1: connected to VDD, M: not connected.

FS1

9

I

Frequency selector pin (standard bi-level ‘1’ or ‘0’). See table on p.1.

Internal 60k

Ω pull-up resistor defaults it to ‘high’ (logical 1).

50 MHz

16

O

50 MHz output. This output is not modulated with Spread Spectrum. This

output can be disabled to tri-state with 50M_EN.

25 MHz/25M_EN

18

B

25 MHz output, not modulated with Spread Spectrum. Bi-directional pin: at

power-up, the input value 25M_EN is latched-in. If 25M_EN (25MHz output

enable) is low, the pin will be disabled to tri-state after power-up, if

25M_EN is high, the out pin will be enabled and provide a 25 MHz output

signal after power-up. Internal 60k

Ω pull-up resistor defaults it to ‘high’

(logical 1).

50M_EN

19

I

50 MHz output enable pin. Disables the 50MHz output to tri-state if ‘low’

(logical 0). Internal 60k

Ω pull-up resistor defaults it to ‘high’ (logical 1).

FUNCTIONAL DESCRIPTION

Selectable spread spectrum and output frequencies

The PLL650-04 provides selectable spread spectrum modulation and selectable output frequencies for the CLKOUT signal.

Selection is made by connecting specific pins to a logical “zero” or “one”, according to the frequency and spread spectrum

selection tables shown on page 1.

In order to reduce the number of pins on the chip, the PLL650-04 uses bi-directional pins that serve as inputs upon power-up,

and as outputs as soon as the inputs have been latched.

Pins 2 (SSTE) is a bi-directional pin used as input to enable/disable the spread spectrum modulation upon power-up, and used

as XOUT crystal connection after the SSTE input signal has been latched. Pin 18 (25M_EN) is a bi-directional pin used to

enable/disable the 25MHz output upon power-up. After the input signal has been latched, pin 18 will serve as 25 MHz output or

will be disabled, depending on the power-up value of 25M_EN.