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Integrated Circuit Systems |
MK1491-09
AMD Geode™ GX2 Clock Source
Description
The MK1491-09 is a low-cost, low-jitter,
high-performance clock synthesizer for AMD’s
Geode-based computer and portable appliance
applications. Using patented analog Phased-Locked
Loop (PLL) techniques, the device accepts a 14.318
MHz crystal input to produce multiple output clocks. It
provides selectable PCI local bus clocks, 48 MHz
clocks for Super I/O and USB, as well as multiple
Reference outputs.
The device has multiple power-down modes to reduce
power consumption.
Block Diagram
VDD
6
GND
6
Features
• Packaged in 28-pin SSOP (209 mil body)
• Available in Pb (lead) free packaged
• Provides all critical timing for the AMD Geode
companion chip
• Four selectable PCI clocks
• Three LPC interface clocks
• One Fixed 66 MHz clock
• 2 Reference clocks
• 48 MHz USB and 48 MHz IO support
• Power down mode
• Low EMI Enable pin reduces EMI radiation on PCI
clocks, LCLKS, and 66 MHz clock
• Operating voltage of 3.3 V ±5%
Sel66/33#
PD#
Clocks
4 PCI (66/33 MHz)
3 LCLK (33 MHz)
66 MHz
14.31818 MHz
crystal
XI
XO
Crystal
Oscillator
USB
Clock
48/TS#
48 MHz
REFCLK1
REFCLK0/Spread#
MDS 1491-09 G
1
Revision 080204
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
MK1491-09
AMD Geode™ GX2 Clock Source
Pin Assignment
GND
XI
XO
VDD
LCLK0/33M
LCLK1/33M
GND
VDD
LCLK2/33M
Sel66/33#
GND
VDD
48M
48M/TS#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28 VDD
27 RefCLK0/Spread#
26 RefCLK1
25 VDD
24 PCICLK3/33-66M
23 PCICLK2/33-66M
22 GND
21 GND
20 PCICLK1/33-66M
19 VDD
18 PCICLK0/33-66M
17 PD#
16 66M
15 GND
PCI Frequency Select Table
Sel66/33#
0
1
PCI Frequency
33 MHz
66 MHz
EMI Control
Spread#
0
1
PCI Low EMI
ON
OFF
Spread direction is DOWN.
Pin Descriptions
Pin
Number
1, 7, 11, 15, 21, 22
2
3
4, 8, 12, 19, 25, 28
5, 6, 9
10
13
14
16
17
18, 20, 23, 24
26
27
Pin
Name
GND
XI
XO
VDD
LCLK
Sel66/33#
48M
48M/TS#
66M
PD#
PCICLK
RefCLK1
RefCLK0/
Spread#
Pin
Type
Pin Description
P Connect to Ground.
I Crystal connection. Connect to a 14.31818 MHz crystal or input clock.
O Crystal connection. Connect to a 14.31818 MHz crystal, or leave
unconnected.
P Connect to 3.3 V.
O 33 MHz low skew clock outputs.
I Selects frequency on PCICLK.
O 48 MHz clock output.
I/O 48 MHz clock output. TS# is high at power-up.
O 66 MHz clock output.
I Power-down input (see table on page 3).
O 33 to 66 MHz PCI synchronous clock outputs with low skew.
O Buffered reference output of 14.31818 MHz.
I/O Buffered reference output of 14.31818 MHz. Spread select at
power-up. For Spread#, see table above.
KEY: I = Input, TI = Tri-level, O = Output, P = Power supply connection, (T)I/O = Input on power up,
becomes an Output after 10 ms, Weak internal pull-up resistors are present on TS#, Spread#, PD#, and
Sel66/33.
MDS 1491-09 G
2
Revision 080204
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
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