ICS8431-11 Datasheet, PDF (1/13 Pages) Integrated Circuit Systems – 255MHZ, LOW JITTER, LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS8431-11
255MHZ, LOW JITTER,
LVPECL FREQUENCY SYNTHESIZER
GENERAL DESCRIPTION
The ICS8431-11 is a general purpose clock
,&6
frequency synthesizer for IA64/32 application and
HiPerClockS™ _{a member of the HiPerClockS™ family of High}
Performance Clock Solutions from ICS. The VCO
operates at a frequency range of 190MHz to
510MHz providing an output frequency range of 95MHz to
255MHz. The output frequency can be programmed using the
parallel interface, M0 thru M8, to the configuration logic.
Spread spectrum clocking is programmed via the control
inputs SSC_CTL0 and SSC_CTL1.
Programmable features of the ICS8431-11 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. Un-
like other synthesizers, the ICS8431-11 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
connnected 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.
FEATURES
• Fully integrated PLL
• Differential 3.3V LVPECL output
• Programmable PLL loop divider for generating a variety of
output frequencies.
• Crystal oscillator interface
• Spread Spectrum Clocking (SSC) fixed at 1/2% modulation
for environments requiring ultra low EMI
• Typical RMS cycle-to-cycle jitter 2.6 ps
• LVTTL / LVCMOS control inputs
• PLL bypass modes supporting in-circuit testing and on-chip
functional block characterization
• 3.3V supply voltage
• 28 lead SOIC
• 0°C to 85°C ambient operating temperature
BLOCK DIAGRAM
XTAL1
XTAL2
OSC
÷ 16
PHASE
DETECTOR
PLL
VCO
÷2
÷M
M0:M8
Configuration
Logic
SSC
Control
Logic
PIN ASSIGNMENT
FOUT
nFOUT
TEST_I/O
M0 1
M1 2
M2 3
M3 4
M4 5
M5 6
M6 7
M7 8
M8 9
SSC_CTL0 10
SSC_CTL1 11
VEE 12
TEST_I/O 13
VDD 14
28 nP_LOAD
27 VDDI
26 XTAL2
25 XTAL1
24 nc
23 nc
22 VDDA
21 VEE
20 MR
19 nc
18 VDDO
17 FOUT
16 nFOUT
15 VEE
ICS8431-11
28-Lead SOIC
M Package
Top View
nP_LOAD
ICS8431CM-11
SSC_CTL0 SSC_CTL1
www.icst.com/products/hiperclocks.html
1
REV. A JULY 11, 2001