ICSI ICS8431-21 User Manual

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Integrated
Circuit
Systems, Inc.

GENERAL DESCRIPTION

ICS

HiPerClockS™

providing an output frequency range of 62.5MHz to 350MHz.
The output frequency can be programmed using the parallel in­terface, M0 through M8 to the configuration logic, and the output
divider control pin, DIV_SEL. Spread spectrum clocking is pro­grammed via the control inputs SSC_CTL0 and SSC_CTL1.

Programmable features of the ICS8431-21 support four op­erational modes. The four modes are spread spectrum clock­ing (SSC), non-spread spectrum clock and two test modes
which are controlled by the SSC_CTL[1:0] pins. Unlike other
synthesizers, the ICS8431-21 can immediately change
spread-spectrum operation without having to reset the device.

In SSC mode, the output clock is modulated in order to achieve
a reduction in EMI. In one of the PLL bypass test modes, the
PLL is disconnected as the source to the differential output
allowing an external source to be connected to the TEST_I/O
pin. This is useful for in-circuit testing and allows the differen­tial output to be driven at a lower frequency throughout the
system clock tree. In the other PLL bypass mode, the oscilla­tor divider is used as the source to both the M and the Fout
divide by 2. This is useful for characterizing the oscillator and
internal dividers.

The ICS8431-21 is a general purpose clock fre­quency synthesizer for IA64/32 application and a
member of the HiPerClockS™ family of High Per­formance Clock Solutions from ICS. The VCO op­erates at a frequency range of 250MHz to 700MHz

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

FEATURES

• Fully integrated PLL

• Differential 3.3V LVPECL output

• Crystal oscillator interface

• Output frequency range: 62.5MHz to 350MHz

• Crystal input frequency range: 14MHz to 25MHz

• VCO range: 250MHz to 700MHz

• Programmable PLL loop divider for generating a variety

of output frequencies

• Spread Spectrum Clocking (SSC) fixed at 1/2% modulation

for environments requiring ultra low EMI

• PLL bypass modes supporting in-circuit testing and on-chip

functional block characterization

• Cycle-to-cycle jitter: 30ps (maximum)

• 3.3V supply voltage

• 0°C to 85°C ambient operating temperature

• Replaces ICS8431-01 and ICS8431-11

• Lead-Free package fully RoHS compliant

BLOCK DIAGRAM PIN ASSIGNMENT

nP_LOAD

M0

V

M1
M2
M3
M4
M5
M6
M7
M8

V

1
2
3
4
5
6
7
8
9
10
11
12

EE

13
14

CC

XTAL_IN

XTAL_OUT

OSC

÷ 16

PHASE

DETECTOR

÷ M

PLL

VCO

÷2

÷4

FOUT
nFOUT

SSC_CTL0
SSC_CTL1

TEST_I/O

ICS8431-21

TEST_I/O

M0:M8

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

Configuration

Logic

nP_LOAD

SSC_CTL0

SSC

Control

Logic

SSC_CTL1

DIV_SEL

1

7.5mm x 18.05mm x 2.25mm package body

28-Lead SOIC

M Package

Top View

28
27
26
25
24
23
22
21
20
19
18
17
16
15

V

CC

XTAL_IN
XTAL_OUT
nc
nc
V

CCA

VEE
MR
DIV_SEL
V

CCO

FOUT
nFOUT
V

EE

Integrated
Circuit
Systems, Inc.

FUNCTIONAL DESCRIPTION

The ICS8431-21 features a fully integrated PLL and therefore
requires no external components for setting the loop bandwidth.
The output of the oscillator is divided by 16 prior to the phase
detector. With a 16MHz crystal this provides a 1MHz reference
frequency. The VCO of the PLL operates over a range of 250MHz
to 700MHz. The output of the M divider is also applied to the phase
detector.

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

The PLL loop divider or M divider is programmed by using
inputs M0 through M8. While the nP_LOAD input is held LOW,
the data present at M0:M8 is transparent to the M divider. On
the LOW-to-HIGH transition of nP_LOAD, the M0:M8 data is
latched into the M divider and any further changes at the
M0:M8 inputs will not be seen by the M divider until the next
LOW transition on nP_LOAD.

The phase detector and the M divider force the VCO output
frequency to be M times the reference frequency by adjusting
the VCO control voltage. Note that for some values of M (ei­ther too high or too low), the PLL will not achieve lock. The
output of the VCO is scaled by a divider prior to being sent to
the LVPECL output buffer. The divider provides a 50% output
duty cycle.

The programmable features of the ICS8431-21 support four
output operational modes and a programmable M divider and
output divider. The four output operational modes are spread
spectrum clocking (SSC), non-spread spectrum clock and
two test modes and are controlled by the SSC_CTL[1:0] pins.

The relationship between the VCO frequency, the crystal fre­quency and the M divider is defined as follows:

fxtal

fVCO =

The M value and the required values of M0:M8 for programming

FOUT

Table 3B

fVCO

=

the VCO are shown in
Function Table. The frequency out is defined as follows:

For the ICS8431-21, the output divider may be set to either ÷2
or ÷4 by the DIV_SEL pin. For an input of 16 MHz, valid
M values for which the PLL will achieve lock are defined as:
250 ≤ M ≤ 511.

x

M

16

, Programmable VCO Frequency

fxtal x M

=

N

16 x N

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

2

Integrated
Circuit
Systems, Inc.

TABLE 1. PIN DESCRIPTIONS

rebmuNemaNepyTnoitpircseD

,4,3,2,1

7,6,5

9,88M-7MtupnIpulluP

11,01

12,51,21V

31O/ITSET

72,41V

71,61TUOF,TUOFntuptuO .slevelecafretniLCEPVLV3.3.rezisehtnysehtrofstuptuolaitnereffiD

8

1V

91LES_VIDtupnInwodlluP

02RMtupnInwodlluP

22V

42,32cndesunU.tcennocoN

62,52

82DAOL_PntupnInwodlluP

pulluP

:ETON

6M-0MtupnInwodlluP

,0LTCCSS

1LTCCSS

EE

CC

OCC

ACC

,TUO_LATX

NI_LATX

dna

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

noitisnartHGIH-ot-WOLnodehctalataD.stupniredividM

slevelecafretnisnipLTTVL/SOMCVL.tupniDAOL_Pnfo

.

tupnIpulluP.sleveleca

rewoPVllatcennoC.snipylppusevitageN
/tupnI

tuptuO

rewoP.nipylppuseroC

rewoP.nipylppustuptuO

MCVL

.slevelecafretniLTTVL/SO

rewoP.nipylppusgolanA

tupnI

csolatsyrC

.tuptuoehtsiTUO_LATX

nwodlluP

fretniSOMCVL/LTTVL.sniplortnocCCS

EE

.dnuorgdraobotsnip

.elbaTnoitcnuFA3elbaTnidenifedsademmargorP

.TUOFrofeulavedividtuptuoehtsenimreteD

erasredividlanretnieht,HGIHcigolnehW.teseRretsaMhgiHevitcA

otTUOFtuptuoeurtehtgnisuacteser

tuptuodetrevniehtdnawolog

ehtdnasredividlanretnieht,WOLcigolnehW.hgihogotTUOFn

onseodRMfonoitressA.delbaneerastuptuo

TdnaMdedaoltceffet

.slevelecafretniLTTVL/SOMCVL.seulav

.tupniehtsiNI_LATX.ecafretnirotalli

0M:8MtatneserpatadnehwsenimreteD.tupnidaollellaraP

levelecafretniSOMCVL/LTTVL.redividMotnidedaolsi

.s

.seulavlacipytrof,scitsiretcarahCniP,2elbaTeeS.srotsisertupnilanretniotrefer

TABLE 2. PIN CHARACTERISTICS

lobmySretemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

C

NI

R

PULLUP

R

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

NWODLLUP

ecnaticapaCniPtupnI 4Fp

rotsiseRpulluPtupnI 15kΩ

rotsiseRnwodlluPtupnI 15kΩ

3

Integrated
Circuit
Systems, Inc.

TABLE 3A. SSC CONTROL INPUT FUNCTION TABLE

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

stupnI

1LTC_CSS0LTC_CSS

00 lanretn

01LLPdelbanE

10 lanretxEdelbasiDklCtseTklCtseTtupnI

11 LLPdelbasiD

U:1ETON

O/I_TSET

ecruoS

IdelbasiDLATXf ÷ 23LATXf ÷ 46

CSS

0LES_VID1LES_VID

MxLATXf

23

MxLATXf

23

.noitaziretcarahcdnagubedesuohnirofdes

TUOFn,TUOF

ATXf

46

46

TABLE 3B. PROGRAMMABLE VCO FREQUENCY FUNCTION TABLE (NOTE 1)

ycneuqerFOCV

)zHM(

052052 0 11111010

152152 0 11111011

252252 0 11111100

352352 0 11111101

• • •••••••••

• • •••••••••

805805 111111100

905905 111111101

015015 111111110

115115 111111111

sA:1ETON

tnuoCM

6528214623618421

8M7M6M5M4M3M2M1M0M

.latsyrczHM61asemus

stuptuO

O/I_TSET

LATXf ÷ 61

÷ M

MxL

MxLATXf

Z-iH

( ≤ klCtseT ≤ )zHM002

Z-iHnoitaludoMCSSoN

zHM1

sedoMlanoitarepO

NdnaM,rotallicso;ssapybLLP

1ETON.edomtsetsredivid

;CSStluafeD

tnecreP½=rotcaFnoitaludoM

;1ETON,edoMssapyBLLP

TABLE 3C. FUNCTION TABLE

stupnI

LES_VIDmuminiMmumixaM

02 521053

14 5.26571

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

eulaVrediviDN

)zHM(ycneuqerFtuptuO

4

Integrated
Circuit
Systems, Inc.

ABSOLUTE MAXIMUM RATINGS

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Supply Voltage, V

Inputs, V

I

Outputs, I
Continuous Current 50mA

CC

O

4.6V

-0.5V to V

+ 0.5V

CC

Surge Current 100mA

Package Thermal Impedance, θ

Storage Temperature, T

STG

TABLE 4A. POWER SUPPLY DC CHARACTERISTICS, V

46.2°C/W (0 lfpm)

JA

-65°C to 150°C

CC

= V

lobmySretemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

V

CC

V

OCC

V

ACC

I

EE

I

ACC

egatloVylppuSeroC 531.33.3564.3V

egatloVylppuStuptuO 531.33.3564.3V

egatloVylppuSgolanA 531.33.3564.3V

tnerruCylppuSrewoP 551Am

tnerruCylppuSgolanA 61Am

TABLE 4B. LVCMOS / LVTTL DC CHARACTERISTICS, V

lobmySretemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

,0LTC_CSS,8M:0M

V

HI

egatloVhgiHtupnI

DAOL_Pn

V

LI

egatloVwoLtupnI

DAOL_Pn

I

HI

I

LI

tnerruChgiHtupnI

tnerruCwoLtupnI

,RM,1LTC_CSS

,O/I_TSET,LES_VID

,0LTC_CSS,8M:0M

,RM,1LTC_CSS

,O/I_TSET,LES_VID

,0LTC_CSS,8M,7M
OI_TSET,1LTC_CSS

LES_VID,6M:0M

RM,DAOL_Pn

,0LTC_CSS,8M,7M
OI_TSET,1LTC_CSS

LES_VID,6M:0M

RM,DAOL_Pn

CC

CCA

= V

V

V

NOTE: Stresses beyond those listed under Absolute
Maximum Ratings may cause permanent damage to the
device. These ratings are stress specifications only. Functional
operation of product at these conditions or any conditions be­yond those listed in the

istics

is not implied. Exposure to absolute maximum rating

DC Characteristics

or

conditions for extended periods may affect product reliability.

= V

= 3.3V±5%, TA = 0°C TO 85°C

CCO

= V

CCA

= 3.3V±5%, TA = 0°C TO 85°C

CCO

2V

CC

3.0-8.0V

V

V=

CC

NI

V=

V

CC

NI

CC

CC

V564.3=5Aµ

V564.3=051Aµ

V,V564.3=

V0=051-Aµ

NI

V,V564.3=

V0=5-Aµ

NI

AC Character-

3.0+V

TABLE 4C. LVPECL DC CHARACTERISTICS, V

CC

= V

CCA

= V

= 3.3V±5%, TA = 0°C TO 85°C

CCO

lobmySretemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

V

HO

V

LO

V

GNIWS

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

egatloVwoLtuptuO1ETON;V

1ETON;egatloVhgiHtuptuOV

4.1-V

OCC

0.2-V

OCC

9.0-V

OCC

7.1-V

OCC

gniwSegatloVtuptuOkaeP-ot-kaeP6.00.1V

05htiwdetanimrettuptuO:1ETON Ω Vot

OCC

5

.tiucriCtseTdaoLtuptuOV3.3,noitceStnemerusaeMretemaraPeeS.V2-

Integrated
Circuit
Systems, Inc.

TABLE 5. CRYSTAL CHARACTERISTICS

retemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

noitallicsOfoedoM latnemadnuF

ycneuqerF 416152zHM

RseireStnelaviuqE 04

ecnaticapaCtnuhS 37Fp

ICS8431-21

350MHZ, LOW JITTER, CRYSTAL OSCILLATOR-

TO-3.3V LVPECL FREQUENCY SYNTHESIZER

)RSE(ecnatsise

Ω

TABLE 6. AC CHARACTERISTICS, V

CC

= V

CCA

= V

= 3.3V±5%, TA = 0°C TO 85°C

CCO

lobmySretemaraPsnoitidnoCtseTmuminiMlacipyTmumixaMstinU

F

TUO

t

j)cc(ti

ycneuqerFtuptuO 5.26053zHM

5,1ETON;rettiJelcyC-ot-elcyCF

≥ zHM0019103sp

TUO

cdoelcyCytuDtuptuO 840525%

t

Rt/F

F

F

F

t

latx

M

FM

CSS

der

ELBATS

emiTllaF/esiRtuptuO%08ot%02002007sp

3,2ETON;egnaRtupnIlatsyrC 416152zHM

4ETON;ycneuqerFnoitaludoMCSSF

4ETON;rotcaFnoitaludoMCSSF

;noitcudeRlartcepS4ETONF

TUO

TUO

TUO

zHM002=9233.33zHK

zHM002=4.06.0%

zHM002=701Bd

tuptuOkcolCelbatSotpu-rewoP 01sm

.noitcesnoitamrofnItnemerusaeMretemaraPehtniserugiFeeS

cnamrofreprettiJ:1ETON

.stupniLATXgnisue

.egnargnitarepoOCVehtnihtiwdilavylnO:2ETON

3ETON

.etoNnoitacilppAotrefer,tupniLATXroF:

:4ETON.delbanegnikcolcmurtcepSdaerpS

.56dradnatSCEDEJhtiwecnadroccanidenifedsiretemarapsihT:5ETON

8431AM-21 www.icst.com/products/hiperclocks.html REV. A APRIL 27, 2005

6