• Complete clock solution to meet requirements of mo-
bile Pentium® and Pentium® II motherboards
— Seven CPU clock outputs (three at 3.3V, and four at
2.5V or 3.3V) with eight selectable clock frequencies.
— Ten 3.3V synchronous PCI clock outputs
— Two 3.3V USB/IR clocks at 48 MHz
— One Keyboard clock at 8 MHz
— One 2.5V IOAPIC clock at 14.318 MHz
— Two 3.3V Ref. clocks at 14.318 MHz
• Dedicated power management for portable systems
— Separate output enable pins for CPU, PCI, and
USB/IR clock sets
•
•
•
•
— Free-running PCI and CPU clocks (see options)
Factory-EPROM programmable output drive and slew
rate for EMI customization
Custom configuration with factory-EPROM program-
mable CPU, PCI, and USB/IR frequencies.
Low skew and low jitter outputs
Available in space-saving 48-pin TSSOP package
voltage applied on pin 42. There are ten PCI clocks, running
at one half the CPU clock frequency. Free-running PCI and
CPU clocks are available as options shown in the selector
guide. Additionally, the part outputs two 3.3V USB/IR clocks at
48 MHz, one Keyboard clock at 8 MHz, one 2.5V IOAPIC clock
at 14.318 MHz, and two 3.3V reference clocks at 14.318 MHz.
The CY2278 family contains several features for output flexi-
bility and power control. The CPU, PCI, USB and IR clock fre-
quencies are all factory EPROM-programmable. Three hard-
ware select inputs support eight CPU clock frequencies from
20 – 75 MHz. Additionally, each of the CPU, PCI, and USB/IR
clock sets can be turned on or off with a dedicated enable input
pin for power management.
The CY2278A outputs are designed for low EMI emissions.
Controlled rise and fall times, unique output driver circuits and
factory-EPROM programmable output drive and slew-rate en-
able optimal configurations for EMI control.
CY2278A Selector Guide
Clock Outputs
CPU@3.3V
CPU@2.5/3.3V
PCI (CPU/2MHz)
USB/IR (48MHz)
KB (8MHz)
IOAPIC (14.318 MHz)
Ref (14.318MHz)
CPU-PCI delay
Notes:
1. One free-running CPU clock.
2. Two free-running PCI clocks.
-1L
3
4
[1]
[2]
-2L
3
4
10
2
1
2
2
0 ns
-3L
3
4
10
[2]
-4L
3
4
10
[2]
2
1
2
2
0 ns
10
2
1
2
2
0 ns
2
1
2
2
1–5 ns
Functional Description
The CY2278A is a Clock Synthesizer/Driver chip for Pentium,
or Pentium II portable PCs designed with the 82430TX or sim-
ilar core-logic chipsets. There are four options available as
shown in the selector guide.
The CY2278A outputs seven CPU clocks, three of which run
at 3.3V and four run at either 2.5V or 3.3V, depending on the
Logic Block Diagram
14.318 MHz
2.5–3.3V Driver
IOAPIC
REF[0-1]
48 MHz
D
CK
/12
8 MHZ
X
IN
X
OUT
OSC.
96 MHz
PLL0
D
CK
/2
USB_RUN
USBCLK/IRCLK
CLK8MHz
2.5–3.3V Driver
XCPUCLK [0-2]
XCPUCLK3_F
on -1L only; not free-
running on -2L, -3L, -4L
CPUCLK [0-2]
SEL2
SEL1
SEL0
EPROM
CPUCLK
PLL1
CPU_RUN
D
CK
/2
D
CK
PCICLK
PCICLK [2-9]
PCICLK_F [0-1]
on -1L, -3L, -4L only; not free-
running on -2L
PCI_RUN
D
CK
D
CK
Intel and Pentium are registered trademarks of Intel Corporation.
Cypress Semiconductor Corporation
•
3901 North First Street
•
San Jose
•
CA 95134
•
408-943-2600
October 14, 1999
CY2278A
Pin Configurations
TSSOP
Top View
REF1
REF0
V
SS
X
IN
X
OUT
V
DDQ3
PCICLK0_F
PCICLK1_F
V
SS
PCICLK2
PCICLK3
PCICLK4
PCICLK5
V
DDQ3
PCICLK6
V
SS
PCICLK7
PCICLK8
V
DDQ3
PCICLK9
CLK8MHz
V
DDQ3
USBCLK
IRCLK
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
2278A-1L
38
37
36
35
34
33
32
31
30
29
28
27
26
25
V
DDQ2
IOAPIC
PWR_DWN
V
SS
XCPUCLK0
XCPUCLK1
V
DDCPU
XCPUCLK2
XCPUCLK3_F
V
SS
CPUCLK0
CPUCLK1
V
DDQ3
CPUCLK2
SEL0
V
SS
SEL1
V
SS
SEL2
CPU_RUN
USB_RUN
PCI_RUN
AV
DD
V
SS
REF1
REF0
V
SS
X
IN
X
OUT
V
DDQ3
PCICLK0
PCICLK1
V
SS
PCICLK2
PCICLK3
PCICLK4
PCICLK5
V
DDQ3
PCICLK6
V
SS
PCICLK7
PCICLK8
V
DDQ3
PCICLK9
CLK8MHz
V
DDQ3
USBCLK
IRCLK
1
2
3
4
5
6
7
8
9
TSSOP
Top View
48
47
46
45
44
43
42
41
V
DDQ2
IOAPIC
PWR_DWN
V
SS
XCPUCLK0
XCPUCLK1
V
DDCPU
XCPUCLK2
XCPUCLK3
V
SS
CPUCLK0
CPUCLK1
V
DDQ3
CPUCLK2
SEL0
V
SS
SEL1
V
SS
SEL2
CPU_RUN
USB_RUN
PCI_RUN
AV
DD
V
SS
40
10
39
2278A-2L
11
38
12
13
14
15
16
17
18
19
20
21
22
23
24
37
36
35
34
33
32
31
30
29
28
27
26
25
TSSOP
Top View
REF1
REF0
V
SS
X
IN
X
OUT
V
DDQ3
PCICLK0_F
PCICLK1_F
V
SS
PCICLK2
PCICLK3
PCICLK4
PCICLK5
V
DDQ3
PCICLK6
V
SS
PCICLK7
PCICLK8
V
DDQ3
PCICLK9
CLK8MHz
V
DDQ3
USBCLK
IRCLK
1
2
3
4
5
6
7
8
9
10
12
13
14
15
16
17
18
19
20
21
22
23
24
48
47
46
45
44
43
42
41
V
DDQ2
IOAPIC
PWR_DWN
V
SS
XCPUCLK0
XCPUCLK1
V
DDCPU
XCPUCLK2
XCPUCLK3
V
SS
CPUCLK0
CPUCLK1
V
DDQ3
CPUCLK2
SEL0
V
SS
SEL1
V
SS
SEL2
CPU_RUN
USB_RUN
PCI_RUN
AV
DD
V
SS
REF1
REF0
V
SS
X
IN
X
OUT
V
DDQ3
PCICLK0_F
PCICLK1_F
V
SS
PCICLK2
PCICLK3
PCICLK4
PCICLK5
V
DDQ3
PCICLK6
V
SS
PCICLK7
PCICLK8
V
DDQ3
PCICLK9
CLK8MHz
V
DDQ3
USBCLK
IRCLK
1
2
3
4
5
6
7
8
9
TSSOP
Top View
48
47
46
45
44
43
42
41
V
DDQ2
IOAPIC
PWR_DWN
V
SS
XCPUCLK0
XCPUCLK1
V
DDCPU
XCPUCLK2
XCPUCLK3
V
SS
CPUCLK0
CPUCLK1
V
DDQ3
CPUCLK2
SEL0
V
SS
SEL1
V
SS
SEL2
CPU_RUN
USB_RUN
PCI_RUN
AV
DD
V
SS
40
39
2278A-3L
38
11
37
36
35
34
33
32
31
30
29
28
27
26
25
40
10
39
2278A-4L
38
11
12
13
14
15
16
17
18
19
20
21
22
23
24
37
36
35
34
33
32
31
30
29
28
27
26
25
2
CY2278A
Pin Summary
Name
V
DDQ3
V
DDQ2
V
DDCPU
AV
DD
V
SS
XTALIN
[3]
XTALOUT
[3]
SEL2
SEL1
SEL0
PCI_RUN
USB_RUN
CPU_RUN
PWR_DWN
XCPUCLK[0:2]
XCPUCLK3_F
CPUCLK[0:2]
PCICLK[2:9]
PCICLK_F[0:1]
CLK8MHZ
IOAPIC
REF[0:1]
USBCLK/IRCLK
Pins
6, 14, 19, 22, 36
48
42
26
3, 9, 16, 25, 31, 33, 39, 45
4
5
30
32
34
27
28
29
46
44, 43, 41
40
38, 37, 35
7, 8
21
47
2, 1
23, 24
Description
3.3V Digital voltage supply
IOAPIC Digital voltage supply, 2.5V
CPU Digital voltage supply, 2.5V or 3.3V
Analog voltage supply, 3.3V
Ground
Reference crystal input
Reference crystal feedback
CPU clock frequency select input, bit 2
CPU clock frequency select input, bit 1
CPU clock frequency select input, bit 0
Control input, stops all PCI clocks except PCICLK_F when driven LOW
Control input, stops all USB/IR clocks when driven LOW
Control input, stops all CPU clocks except XCPUCLK_F when driven LOW
Power down input, shuts down device when driven LOW
2.5V or 3.3V CPU clock outputs
2.5V or 3.3V CPU clock output, free-running on CY2278A-1L only. This output
is not free-running on the -2L, -3L, -4L configurations.
3.3V CPU clock output
PCI clock outputs, free-running on CY2278A-1L, -3L, -4L only. This output is
not free-running on the -2L configuration
8-MHz Keyboard clock output
IOAPIC clock output
Reference clock outputs, 14.318 MHz. REF0 has high drive
USB or IR clock outputs, 48 MHz
10, 11, 12, 13, 15, 17, 18, 20 PCI clock outputs
Note:
3. For best accuracy, use a parallel-resonant crystal, C
LOAD
= 18 pF.
Function Table
SEL2
0
0
0
0
1
1
1
1
SEL1
0
0
1
1
0
0
1
1
SEL0
0
1
0
1
0
1
0
1
XTALIN
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
CPUCLK
75.0 MHz
20.0 MHz
25 MHz
33.33 MHz
50.0 MHz
60.0 MHz
66.67 MHz
40.0 MHz
PCICLK
37.5 MHz
10.0 MHz
12.5 MHz
16.67 MHz
25.0 MHz
30.0 MHz
33.33 MHz
20.0 MHz
REF
IOAPIC
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
14.318 MHz
USBCLK
IRCLK
48.0 MHz
48.0 MHz
48.0 MHz
48.0 MHz
48.0 MHz
48.0 MHz
48.0 MHz
48.0 MHz
CLK8MHZ
8.0 MHz
8.0 MHz
8.0 MHz
8.0 MHz
8.0 MHz
8.0 MHz
8.0 MHz
8.0 MHz
3
CY2278A
Actual Clock Frequency Values
Clock Output
CPUCLK(0,0,0)
CPUCLK(0,0,1)
CPUCLK(0,1,0)
CPUCLK(0,1,1)
CPUCLK(1,0,0)
CPUCLK(1,0,1)
CPUCLK(1,1,0)
CPUCLK(1,1,1)
USBCLK
[4]
CLK8MHz
Target Frequency
(MHz)
75.0 MHz
20.0 MHz
25 MHz
33.33 MHz
50.0 MHz
60.0 MHz
66.67 MHz
40.0 MHz
48.0
8.0
75.0
19.979
24.974
33.298
49.947
60.0
66.654
39.992
48.008
8.001
Actual Frequency
(MHz)
0
–1057
–1057
–1107
–1057
0
–171
–196
167
167
PPM
Maximum Ratings
(Above which the useful life may be impaired. For user guide-
lines, not tested.)
Supply Voltage ..................................................–0.5 to +7.0V
Input Voltage .............................................. –0.5V to V
DD
+0.5
Storage Temperature (Non-Condensing) ... –65°C to +150°C
Max. Soldering Temperature (10 sec) ...................... +260°C
Junction Temperature ............................................... +150°C
Package Power Dissipation .............................................. 1W
Static Discharge Voltage ........................................... >2000V
(per MIL-STD-883, Method 3015, like V
DD
pins tied together)
Operating Conditions
[5]
Parameter
AV
DD
, V
DDQ3
V
DDCPU,
V
DDQ2
T
A
C
L
Description
Analog and Digital Supply Voltage
CPU and IOAPIC Supply Voltage
Operating Temperature, Ambient
Max. Capacitive Load on
XCPUCLK, CPUCLK, USBCLK/IRCLK, CLK8MHZ, REF1,
IOAPIC
PCICLK
REF0
Reference Frequency, Oscillator Nominal Value
14.318
Min.
3.135
2.375
0
Max.
3.465
2.625
70
20
20
30
45
14.318
MHz
Unit
V
V
°C
pF
f
(REF)
Notes:
4. Meets Intel USB clock requirements.
5. Electrical parameters are guaranteed with these operating conditions.
Electrical Characteristics
Parameter
V
IH
V
IL
V
OH
V
OL
Description
High-level Input Voltage
Low-level Input Voltage
Except Crystal Inputs
[6]
Except Crystal Inputs
[6]
I
OH
= 9 mA
XCPUCLK
2.0
0.4
I
OH
= 13 mA IOAPIC
Low-level Output Voltage V
DDCPU
, V
DDQ2
= 2.375V
I
OL
= 13 mA XCPUCLK
I
OL
= 18 mA IOAPIC
V
Test Conditions
Min. Max. Unit
2.0
0.8
V
V
V
High-level Output Voltage V
DDCPU
, V
DDQ2
= 2.375V
4
CY2278A
Electrical Characteristics
Parameter
V
OH
Description
Test Conditions
I
OH
= 23 mA XCPUCLK
I
OH
= 23 mA CPUCLK
I
OH
= 23 mA PCICLK
I
OH
= 23 mA USBCLK
I
OH
= 23 mA CLK8MHZ
I
OH
= 23 mA REF0
I
OH
= 23 mA REF1
V
OL
Low-level Output Voltage V
DDQ3
, AV
DD
, V
DDCPU
= 3.135V
I
OL
= 17 mA XCPUCLK
I
OL
=17 mA
CPUCLK
I
OL
= 17 mA PCICLK
I
OL
= 17 mA USBCLK
I
OL
= 17 mA CLK8MHZ
I
OL
= 17 mA REF0
I
OL
= 17 mA REF1
I
IH
I
IL
I
DD
I
DD
I
DDS
Input High Current
Input Low Current
Power Supply Current
[7]
Power Supply Current
[7]
Power-down Current
V
IH
= V
DD
V
IL
= 0V
V
DDQ3
= 3.465V, V
IN
= 0 or V
DD
, Loaded Outputs,
CPU clocks = 66.67 MHz
V
DDQ3
= 3.465V, V
IN
= 0 or V
DD
, Unloaded Outputs
Current draw in power-down state
–10
+10
10
200
100
150
µA
µA
mA
mA
µA
0.4
V
Min. Max. Unit
2.4
V
High-level Output Voltage V
DDQ3
, AV
DD
, V
DDCPU
= 3.135V
Notes:
6. Crystal inputs have CMOS thresholds.
7. Power supply current will vary with number of outputs which are running. Therefore, power supply current can be calculated with the following formula: to be
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