AV9169CJ-27 데이터 시트보기 (PDF) - Integrated Circuit Systems

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AV9169CJ-27

Frequency Generator for Pentium™™ Based Systems

Integrated Circuit Systems 

ICS9169C-27

Shared Pin Operation -

Input/Output Pins

Shared Pin Operation - Input/Output Pins 5, 12, 13 and 32

on the ICS9169C-27 serve as dual signal functions to the

device. During initial power-up, they act as input pins. The

logic level (voltage) that is present on these pins at this time

is read and stored into a 4-bit internal data latch. At the end

of Power-On reset, (seeAC characteristics for timing values),

the device changes the mode of operation for these pins to

an output function. In this mode the pins produce the

specified buffered clocks to external loads.

To program (load) the internal configuration register for

these pins, a resistor is connected to either the VDD (logic 1)

power supply or the GND (logic 0) voltage potential. A 10

Kilohm(10K) resistor is used to provide both the solid

CMOS programming voltage needed during the power-up

programming period and to provide an insignificant load on

the output clock during the subsequent operating period.

Figs. 1 and 2 show the recommended means of implementing

this function. In Fig. 1 either one of the resistors is loaded

onto the board (selective stuffing) to configure the device’s

internal logic. Figs. 2a and b provide a single resistor loading

option where either solder spot tabs or a physical jumper

header may be used.

Test Mode Operation

The ICS9169C-27 includes a production test verification

mode of operation. This requires that the FS0 and FS1 pins

be programmed to a logic high and the FS2 pin be

programmed to a logic low(see Shared Pin Operation section).

In this mode the device will output the following

frequencies.

Pin

REF

48MHz

24MHz

CPU (1:12)

BUS (1:6)

BSEL=1

BSEL = 0

Frequency

REF

REF/2

REF/4

REF2

REF/4

REF/3

Note: REF is the frequency of either the crystal connected

between the devices X1and X2 or, in the case of a device

being driven by an external reference clock, the frequency

of the reference (or test) clock on the device’s X1 pin.

These figures illustrate the optimal PCB physical layout

options. These configuration resistors are of such a large

ohmic value that they do not effect the low impedance clock

signals. The layouts have been optimized to provide as little

impedance transition to the clock signal as possible, as it

passes through the programming resistor pad(s).

(Resistors are surface mount devices

shown schematically between 5.m. pads)

*use only one programming resistor

Fig. 1

3

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