ICS9250-13 Datasheet, PDF (1/15 Pages) Integrated Circuit Systems – Frequency Generator & Integrated Buffers for PENTIUM/ProTM

Integrated
Circuit
Systems, Inc.
ICS9250 - 13
Frequency Generator & Integrated Buffers for PENTIUM/Pro^TM
General Description
The ICS9250-13 generates all clocks required for high speed
RISC or CISC microprocessor systems such as Intel PentiumPro
or Cyrix. Eight different reference frequency multiplying factors
are externally selectable with smooth frequency transitions.
Spread spectrum may be enabled through I²C programming.
Spread spectrum typically reduces system EMI by 8dB to
10dB. This simplifies EMI qualification without resorting to
board design iterations or costly shielding. The ICS9250-13
employs a proprietary closed loop design, which tightly
controls the percentage of spreading over process and
temperature variations.
Features
• 3.3V outputs: SDRAM, PCI, REF, 48/24MHz
• 2.5V or 3.3V outputs: CPU
• 20 ohm CPU clock output impedance
• 20 ohm PCI clock output impedance
• Skew from CPU (earlier) to PCI clock - 1 to 4 ns,
center 2.6 ns.
• No external load cap for C_L=18pF crystals
• ±250 ps CPU, PCI clock skew
• 400ps (cycle to cycle) CPU jitter
• Smooth frequency switch, with selections from
50 to 83.3 MHz CPU.
• I²C interface for programming
• 2ms power up clock stable time
• Clock duty cycle 45-55%.
• 56 pin 300 mil SSOP package
• 3.3V operation, 5V tolerant input.
Block Diagram
Recomended Application:
• 440LX/EX type chipset Motherboard single chip
clock solution.
Pin Configuration
Power Groups
VDDREF = REF (0:1), X1, X2
VDDPCI = PCICLK_F, PCICLK(0:5)
VDDSDR = SDRAM (0:11), supply for PLL core,
VDD48 = 24MHz, 48MHz
VDDLIOAPIC = IOAPIC
VDDL2CPU = CPUCLK (0:3)
9250-13 Rev A 3/25/99
56-Pin SSOP
* Internal Pull-up Resistor of
120K to VDD on indicated inputs
Pentium is a trademark of Intel Corporation
I²C is a trademark of Philips Corporation
ICS reserves the right to make changes in the device data identified in
this publication without further notice. ICS advises its customers to
obtain the latest version of all device data to verify that any
information being relied upon by the customer is current and accurate.