650R-14ILF(2010) Просмотр технического описания (PDF) - Integrated Device Technology

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Компоненты Описание

производитель

650R-14ILF
(Rev.:2010)

NETWORKING SYSTEM CLOCK

Integrated Device Technology 

ICS650-14

NETWORKING SYSTEM CLOCK

CLOCK SYNTHESIZER

Pin

Number

13

14

15

16

17

18

19

20

Pin

Name

CLKA4

GND

SELA1

VDD

CLKA3

CLKA2

SELA0

SELC

Pin

Type

O

P

TI

P

O

O

TI

TI

Pin Description

Selectable clock output. See table 1.

Connect to ground.

Select pin for CLKA1:4 and CLKA5 outputs. See table 1.

Connect to 3.3 Vor 5 V. Must be same as other VDDs.

Selectable clock output. See table 1.

Selectable clock output. See table 1.

Select pin for CLKA1:4 and CLKA5 outputs. See table 1.

Select pin for CLKC output. See table 3.

Key: XI, XO = crystal connections; I = input; I(Pu) = input with pull-up; O = output; P = power supply connection; TI

= tri-level input

External Components

The ICS650-14 requires a minimum number of external

components for proper operation.

Decoupling Capacitor

Decoupling capacitors of 0.01µF must be connected

between each VDD and GND (pins 4 and 6, pins 16 and 14),

as close to the device as possible. For optimum device

performance, the decoupling capacitor should be mounted

on the component side of the PCB. Avoid the use of vias in

the decoupling circuit.

Series Termination Resistor

When the PCB trace between the clock outputs and the

loads are over 1 inch, series termination should be used. To

series terminate a 50Ω trace (a commonly used trace

impedance) place a 33Ωresistor in series with the clock line,

as close to the clock output pin as possible. The nominal

impedance of the clock output is 20Ω.

Crystal Information

The crystal used should be a fundamental mode (do not use

third overtone), parallel resonant. Crystal capacitors should

be connected from pins X1 to ground and X2 to ground to

optimize the initial accuracy. The value of these capacitors

is given by the following equation:

Crystal caps (pF) = (CL - 6) x 2

In the equation, CL is the crystal load capacitance. For a

crystal with a 16 pF load capacitance, two 20 pF [(16-6) x 2]

capacitors should be used.

IDT™ / ICS™ NETWORKING SYSTEM CLOCK

3

ICS650-14 REV H 051310

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