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January 2000
1.0 Features
•
2.0 Description
Generates clocks required for Intel® i820 based
desktop and workstation systems, including:
The FS6261-01 is a CMOS clock generator IC designed
for high-speed motherboard applications. Two different
frequencies can be selected for the CPU clocks via two
SEL pins. Glitch-free stop clock control of the CPU, AGP
(66MHz) and PCI clocks is provided. A low current
power-down mode is available for mobile applications.
Separate clock buffers provide for a 2.5V voltage range
on the CPU_0:3, CPU/2_0:1 and APIC_0:2 clocks.
♦
Four enabled 2.5V 133/100MHz CPU Front Side
Bus (FSB) clocks
♦
♦
Two 2.5V CPU/2 clocks for synchronous memory
Seven enabled 3.3V PCI bus clocks and one
free-running PCI clock
♦
♦
♦
♦
Four enabled 3.3V 66MHz AGP clocks
Three 2.5V 16.67MHz APIC bus clocks
Two 3.3V 14.318MHz REF clocks
One 3.3V 48MHz USB clock
Figure 2: Pin Configuration
1
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
VSS_R
REF_0
REF_1
VDD_R
VDD_A
APIC_2
APIC_1
APIC_0
VSS_A
VDD_C2
CPU/2_1
CPU/2_0
VSS_C2
VDD_C
CPU_3
CPU_2
VSS_C
VDD_C
CPU_1
CPU_0
VSS_C
VDD
2
3
•
•
CPU clock cycle – cycle jitter < 150ps p-p
4
5
XIN
Non-linear spread-spectrum modulation
(-0.5% at 31.5kHz)
6
XOUT
7
VSS_P
2(.
5
V
8
PCI_F
PCI_1
•
•
Supports test mode and tristate output control
uot
9
upt
Separate CPU-enable, PCI-enable and power-down
inputs with glitch-free stop clock controls on all clocks
for clock control and power management
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
VDD_P
PCI_2
s
)
F
PCI_3
2S-601
VSS_P
PCI_4
PCI_5
Figure 1: Block Diagram
VDD_P
PCI_6
XIN
Crystal
Oscillator
PCI_7
XOUT
VDD_R
VSS_P
VSS_66
CK66_0
CK66_1
VDD_66
VSS_66
CK66_2
CK66_3
VDD_66
SEL133/100#
VSS
REF_0:1
VSS_R
PCI_STOP#
CPU_STOP#
PWR_DWN#
SS_EN#
SEL_1
SEL_0:1
SS_EN#
PLL
VDD_C2
SEL_133/100#
÷2
CPU/2_0:1
VSS_C2
SEL_0
VDD_A
÷6 or
÷8
VDD_48
CK48
delay
APIC_0:2
VSS_A
PWR_DWN#
CPU_STOP#
VSS_48
VDD_C
CPU_0:3
VSS_C
56-pin SSOP
(2.5V outputs)
VDD_66
Table 1: CPU/PCI Frequency Selection
÷1½
or ÷2
delay
CK66_0:3
VSS_66
SEL_133/100#
SEL_1
SEL_0
CPU (MHz)
PCI (MHz)
VDD_P
÷3 or
÷4
delay
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
tristate
(reserved)
100
tristate
(reserved)
33.33
PCI_F
PCI_1:7
PCI_STOP#
VSS_P
100
33.33
VDD_48
CK48
÷3 or
÷4
PLL
XIN/2
XIN/6
VSS_48
(reserved)
133
(reserved)
33.33
FS6261-01
133
33.33
Intel and Pentium are registered trademarks of Intel Corporation. Spread spectrum modulation is licensed under US Patent No. 5488627, Lexmark International, Inc. American Microsystems, Inc.
reserves the right to change the detail specifications as may be required to permit improvements in the design of its products.
1.31.00
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