C9843
Clock Generator for Pentium
®
Systems with SDRAM Support
Preliminary
Product Features
•
•
•
•
•
•
•
•
•
Two CPU clocks (2.5V)
One MREF clock (2.5V)
Six PCI clocks (3.3V)
One IOAPIC clocks (2.5V)
One 3V48M (48 MHz, 3.3V)USB
One 2V48M (48 MHz, 2.5V)DOT
Two REF’s (14.318 MHz, 3.3V)
Nine SDRAM clocks (buffered copies of
SDRAM_IN)
EMI reducing Spread Spectrum (SS) technology
SEL1
0
0
1
1
0
0
1
1
Product Description
The C9843 is a clock generator solution that supports
Intel Pentium III based SDRAM memory architecture
designs. It operates at multiple CPU frequency of 66
MHz and supplies the SDRAM clocks required to drive
the up to 2 Desktop DIMM memory modules. Supplied
in a 48 pin SSOP package it includes the patented and
design proven Spread Spectrum EMI noise reduction
technology.
This device integrates IMI Spread
Spectrum clock technology to produce a low EMI device
in a small 48 pin SSOP package.
Select Input Functionality
SEL2
0
0
0
0
1
1
1
1
SEL0
0
1
0
1
0
1
0
1
CPU0
CPU1_ICH, MREF
66.8 MHz
68.5 MHz
70 MHz
66.6 MHz
75 MHz
83.3 MHz
90 MHz
100.2 MHz
SDRAM
(0:7, MTH)
SDRAM_IN
SDRAM_IN
SDRAM_IN
SDRAM_IN
SDRAM_IN
SDRAM_IN
SDRAM_IN
SDRAM_IN
2V48
3V48
48 MHz
48 MHz
48 MHz
48 MHz
48 MHz
48 MHz
48 MHz
48 MHz
PCI (0:5)
IOAPIC
33.4MHz
34.25MHz
35.0MHz
33.3MHz
30.0MHz
33.3MHz
30.0MHz
33.4MHz
REF
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
Table 1
Block Diagram
VDD
VDD
Pin Configuration
SEL2/REF0
XIN
XOUT
OSC
VDD
REF1
CPU0
VDDC
VDD
VDDI
SEL2
CPU1_ICH
IOAPIC
VDDC
PLL1
SEL1
SEL0
MREF66
VDD
PCI (2:5)
SEL0/PCI0
VDD
SEL1/PCI1
SDRAM_IN
VDD
VDD
SDRAM_MTH
VDD
PLL2
VDDI
SDRAM(0:7)
2V48M
VDD
SDATA
SCLK
I2C
Control
Logic
3V48M0
2V48M
3V48M
VDD
VSS
XIN
XOUT
VSS
SEL2/REF0
REF1
VDD
SEL0/PCI0
SEL1/PCI1
VSS
VDD
PCI2
PCI3
PCI4
PCI5
SCLK
VDD
VSS
SDATA
SDRAM_IN
SDRAM7
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
VDDI
IOAPIC
VSS
VDDC
CPU0
CPU1_ICH
VDDC
VSS
MREF
VDD
SDRAM_MTH
SDRAM0
VDD
VSS
SDRAM1
SDRAM2
SDRAM3
VSS
VDD
SDRAM4
SDRAM5
VDD
VSS
SDRAM6
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035, USA TEL: 408-263-6300. FAX 408-263-6571
http://www.imicorp.com
Rev 1.0
3/30/2000
Page 1 of 13
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