ICST MK1432STR, MK1434S, MK1434STR, MK1432S Datasheet
MK1432/MK1434
Green PC and Local Bus Clock Source
Description
The MK1432 and MK1434 are low cost, high
performance triple clock synthesizers for green PC and
local bus desktop and notebook applications. Using
analog Phase-Locked Loop (PLL) techniques, the
devices accept a 14.318 MHz crystal input to produce
multiple output clocks up to 100 MHz. They provide
selectable 2XCPU and CPU, selectable local bus clock,
ISA clock, and one fixed peripheral clock. The chips
support PCI and VL buses. The fixed clock is either
24MHz or 40MHz. The devices can operate at 5V or
3.3V up to and including 80MHz on the 2XCPU clock.
The Power Saving pin causes the CPU clocks to
smoothly transition to 33.33 MHz for Pentiums, and
16.67 MHz for 486DX4. In addition, a single pin can be
made to slow DX2s to 8 MHz.
Block Diagram
VDD GND
Features
• Packaged in 16 pin narrow (150 mil) SOIC
• Supports all Pentium™ Processor timing specs
• Supports synchronous and asynchronous local bus
• Selectable local bus frequencies of 25, 33, or
50MHz
• SCSI or VL bus 40MHz clock on MK1434
• Floppy or super I/O clock on MK1432
• Single Power Saving pin switches to low power
mode (for 486 and Pentium)
• 5V or 3.3V (up to 80MHz) operation
• Smooth transitions for Pentium and 486 based
Green PC
• Low skew (<250ps) Pentium compatible
2X and 1X outputs
• Duty cycle of 45/55 up to 100 MHz
• 25mA output drive capability at TTL levels
• Compatible with all popular microprocessors
• Packaged in 16 pin narrow SOIC
• For Early Clock support, consult MicroClock
FS0
FS1
FS2
PS
BCLKS
X1
14.318 MHz
crystal
X2
MDS 1432 G 1 Revision 060101
Crystal
Oscillator
CPU
Clocks
Local
Bus
Clock
Fixed
Clock
÷2
Output
Buffer
Output
Buffer
Output
Buffer
Output
Buffer
Output
Buffer
2XCPU
CPU
BCLK
40.00 (MK1434)
or 24.00 MHz
(MK1432)
14.318 MHz
Integrated Circuit Systems, Inc. • 525 Race Street • San Jose • CA • 95126 • (408)295-9800 • www.icst.com
Power Saving pin. Smoothly changes CPU to/from 33.33 and 16.67 MHz. IPU.
Pin Assignment
FS2
X2
X1
VDD
GND
BCLK
24M
PS
1
2
3
4
5
6
7 10
8
MK1432/MK1434
Green PC and Local Bus Clock Source
16
15
14
13
12
11
9
FS1
2XCPU
CPU
VDD
GND
14.3M
FS0
BCLKS
FS2
X2
X1
VDD
GND
BCLK
40M
PS
1
15
2
3
14
4
13
5
12
6
11
7 10
8
16
9
FS1
2XCPU
CPU
VDD
GND
14.3M
FS0
BCLKS
CPU Clock Decoding Table (in MHz)
PS FS2 FS1 FS0 2XCPU CPU
1 0 0 0 16.00 8.00
1 0 0 1
50.00 note3
1 0 1 0 80.00 40.00
1 0 1 1 75.00 37.50
1 1 0 0 40.00 20.00
1 1 0 1 50.00 25.00
1 1 1 0 66.66 33.33
1 1 1 1 60.00 30.00
0 X X X 33.33 16.67
Pin Descriptions
Local Bus Clock Decoding Table (in MHz)
BCLKS BCLK (MHz)
0 25.00
M 33.33
1 50.00
Notes:
1. Actual frequencies are within 0.05% of those shown.
2. Transitions between mean frequencies on any CPU pin are
smooth, and do not violate Intel’s 0.1% per cycle specification.
3. These selections are not guaranteed to operate at 3V.
4. M = mid level. Leave pin tri-stated, unconnected, or floating to
select this level.
5. X = don’t care (either 0 or 1).
1432 1434 Name Type Description
1 1 FS2 I Select 2 for 2XCPU and CPU frequencies. See table above. Internal Pull-Up.
2 2 X2 O Crystal connection. Connect to 14.31818 MHz crystal.
3 3 X1 I Crystal connection. Connect to 14.31818 MHz crystal or clock.
4 4 VDD P Connect to +5V or 3.3V. Must be same voltage as pin 13.
5 5 GND P Connect to ground.
6 6 BCLK O Local Bus Clock output. See table above.
7 - 24M O 24.00 MHz clock output (MK1432 only).
- 7 40M O 40.00 MHz clock output (MK1434 only).
8 8 PS I
9 9 BCLKS TI Local Bus Clock Select pin. See table above.
10 10 FS0 I Select 0 for 2XCPU and CPU frequencies. See table above. Internal Pull-Up.
11 11 14.3M O 14.318 MHz Reference Clock Output.
12 12 GND P Connect to ground.
13 13 VDD P Connect to +5V or 3.3V. Must be same voltage as pin 4.
14 14 CPU O CPU Clock output. See table above for frequencies.
15 15 2XCPU O 2X CPU Clock output. See table above for frequencies.
16 16 FS1 I Select 1 for 2XCPU and CPU frequencies. See table above. Internal Pull-Up.
Key: TI = Tri-level Input, I = Input, O = output, P = power supply connection
MDS 1432 G 2 Revision 060101
Integrated Circuit Systems, Inc. • 525 Race Street • San Jose • CA • 95126 • (408)295-9800 • www.icst.com
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