September 2005
rev 1.4
3.3V Zero-Delay Buffer
General Features
•
Zero input - output propagation delay, adjustable by
capacitive load on FBK input.
•
Multiple configurations - Refer “ASM5P2308A
Configurations “ Table.
•
•
Input frequency range: 15MHz to 133MHz
Multiple low-skew outputs.
•
•
•
Output-output skew less than 200pS.
Device-device skew less than 700pS.
The
ASM5P2308A
is
ASM5P2308A
allows the input clock to be directly applied to the outputs
for chip and system testing purposes.
Multiple ASM5P2308A devices can accept the same input
clock and distribute it. In this case the skew between the
outputs of the two devices is guaranteed to be less than
700pS.
available
in
five
different
Two banks of four outputs, tri-stateable by two select
inputs.
configurations(Refer “ASM5P2308A Configurations” Table).
The ASM5P2308A-1 is the base part, where the output
frequencies equal the reference if there is no counter in the
feedback path. The ASM5P2308A-1H is the high-drive
version of the -1 and the rise and fall times on this device
are much faster.
•
Less than 200pS cycle-to-cycle jitter
(-1, -1H,-2, -3, -4, -5H).
•
•
•
•
Available in 16 pin SOIC and TSSOP packages.
3.3V operation.
Advanced 0.35µ CMOS technology.
Industrial temperature available.
The ASM5P2308A-2 allows the user to obtain 2X and 1X
frequencies on each output bank. The exact configuration
Functional Description
ASM5P2308A is a versatile, 3.3V zero-delay buffer
designed to distribute high-speed clocks. It is available in a
16 pin package. The part has an on-chip PLL which locks
to an input clock presented on the REF pin. The PLL
feedback is required to be driven to FBK pin, and can be
obtained from one of the outputs. The input-to-output
propagation delay is guaranteed to be less than 250pS,
and the output-to-output skew is guaranteed to be less than
200pS.
and output frequencies depends on which output drives the
feedback pin. The ASM5P2308A-3 allows the user to
obtain 4X and 2X frequencies on the outputs.
The ASM5P2308A-4 enables the user to obtain 2X clocks
on all outputs.
The ASM5P2308A-5H is a high-drive version with REF/2
on both banks. Thus, the part is extremely versatile, and
can be used in a variety of applications.
The ASM5P2308A has two banks of four outputs each,
which can be controlled by the select inputs as shown in
the Select Input Decoding Table. The select input also
Alliance Semiconductor
2575 Augustine Drive
•
Santa Clara, CA
•
Tel: 408.855.4900
•
Fax: 408.855.4999
•
www.alsc.com
Notice: The information in this document is subject to change without notice.
September 2005
rev 1.4
Block Diagram
/2
REF
/2
FBK
PLL
MUX
CLKA1
Extra Divider (-5H)
Extra Divider (-3, -4)
CLKA2
CLKA3
CLKA4
S2
Select Input
Decoding
S1
/2
CLKB1
Extra Divider (-2, -3)
CLKB2
CLKB3
CLKB4
ASM5P2308A
ASM5P2308A
Select Input Decoding for ASM5P2308A
S2
0
0
1
1
S1
0
1
0
1
Clock A1 - A4
Three-state
Driven
Driven
1
Driven
Clock B1 - B4
Three-state
Three-state
Driven
Driven
Output Source
PLL
PLL
Reference
PLL
PLL Shut-Down
Y
N
Y
N
ASM5P2308A Configurations
Device
ASM5P2308A-1
ASM5P2308A-1H
ASM5P2308A-2
ASM5P2308A-2
ASM5P2308A-3
ASM5P2308A-3
ASM5P2308A-4
ASM5P2308A-5H
Feedback From
Bank A or Bank B
Bank A or Bank B
Bank A
Bank B
Bank A
Bank B
Bank A or Bank B
Bank A or Bank B
Bank A Frequency
Reference
Reference
Reference
2 X Reference
2 X Reference
4 X Reference
2 X Reference
Reference /2
Bank B Frequency
Reference
Reference
Reference /2
Reference
Reference or Reference
2
2 X Reference
2 X Reference
Reference /2
Note:
1. Outputs are non- inverted on ASM5P2308A-2 and ASM5P2308A-3 in bypass mode, S2 = 1 and S1 = 0.
2. Output phase is indeterminant (0° or 180° from input clock). If phase integrity is required, use the ASM5P2308A-2.
3.3V Zero Delay Buffer
Notice: The information in this document is subject to change without notice.
2 of 18
September 2005
rev 1.4
Zero Delay and Skew Control
All outputs should be uniformly loaded to achieve Zero Delay between input and output.
ASM5P2308A
1500
1000
REF- Input to CLKA/CLKB Delay
500
0
-30
-500
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
-1000
-1500
Output Load Difference: FBK Load - CLKA/CLKB Load (pF)
To close the feedback loop of the ASM5P2308A, the FBK pin can be driven from any of the eight available output pins. The
output driving the FBK pin will be driving a total load of 7pF plus any additional load that it drives. The relative loading of this
output (with respect to the remaining outputs) can adjust the input output delay. This is shown in the above graph.
For applications requiring zero input-output delay, all outputs including the one providing feedback should be equally loaded.
If input-output delay adjustments are required, use the above graph to calculate loading differences between the feedback
output and remaining outputs. For zero output-output skew, be sure to load outputs equally.
3.3V Zero Delay Buffer
Notice: The information in this document is subject to change without notice.
3 of 18
September 2005
rev 1.4
Pin Configuration
REF 1
CLKA1 2
CLKA2 3
V
DD
4
ASM5P2308A
GND 5
CLKB1 6
CLKB2 7
S2
8
16 FBK
15 CLKA4
14 CLKA3
13 V
DD
12 GND
11 CLKB4
10 CLKB3
9
S1
ASM5P2308A
Pin Description for ASM5P2308A
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pin Name
REF
3
Description
Input reference frequency, 5V tolerant input
Buffered clock output, bank A
Buffered clock output, bank A
3.3V supply
Ground
CLKA1
4
CLKA2
4
V
DD
GND
CLKB1
CLKB2
S2
S1
5
5
4
4
Buffered clock output, bank B
Buffered clock output, bank B
Select input, bit 2
Select input, bit 1
Buffered clock output, bank B
Buffered clock output, bank B
Ground
3.3V supply
CLKB3
4
CLKB4
4
GND
V
DD
CLKA3
CLKA4
FBK
4
4
Buffered clock output, bank A
Buffered clock output, bank A
PLL feedback input
Notes:
3. Weak pull-down.
4. Weak pull-down on all outputs.
5. Weak pull-up on these inputs.
3.3V Zero Delay Buffer
Notice: The information in this document is subject to change without notice.
4 of 18
September 2005
rev 1.4
Absolute Maximum Ratings
Parameter
Supply Voltage to Ground Potential
DC Input Voltage (Except REF)
DC Input Voltage (REF)
Storage Temperature
Max. Soldering Temperature (10 sec)
Junction Temperature
Static Discharge Voltage (As per JEDEC STD22- A114-B)
ASM5P2308A
Min
-0.5
-0.5
-0.5
-65
Max
+7.0
V
DD
+ 0.5
7
+150
260
150
2000
Unit
V
V
V
°C
°C
°C
V
Note: These are stress ratings only and functional usage is not implied. Exposure to absolute maximum ratings for prolonged periods can affect device
reliability.
Operating Conditions for ASM5P2308A Commercial Temperature Devices
Parameter
V
DD
T
A
C
L
C
L
C
IN
Supply Voltage
Operating Temperature (Ambient Temperature)
Load Capacitance, below 100MHz
Load Capacitance, from 100MHz to 133MHz
Input Capacitance
6
Description
Min
3.0
0
Max
3.6
70
30
15
7
Unit
V
°C
pF
pF
pF
Note:
6. Applies to both Ref Clock and FBK.
Electrical Characteristics for ASM5P2308A Commercial Temperature Devices
Parameter
V
IL
V
IH
I
IL
I
IH
V
OL
V
OH
Description
Input LOW Voltage
Input HIGH Voltage
Input LOW Current
Input HIGH Current
Output LOW Voltage
7
Output HIGH Voltage
7
Test Conditions
Min
2.0
Max
0.8
Unit
V
V
µA
µA
V
V
V
IN
= 0V
V
IN
= V
DD
I
OL
= 8mA (-1, -2, -3, -4)
I
OH
= 12mA (-1H, -5H)
I
OL
= -8mA (-1, -2, -3, -4)
I
OH
= -12mA (-1H, -5H)
Unloaded outputs 100MHz REF
(-2,-3,-4)
(-1H,-5H)
2.4
50.0
100.0
0.4
49
60
34
18
mA
I
DD
Supply Current
8
Select inputs at V
DD
or GND
Unloaded outputs, 66MHz REF (-1, -2, -3, -4)
Unloaded outputs, 33MHz REF (-1, -2, -3, -4)
Note:
7. Parameter is guaranteed by design and characterization. Not 100% tested in production.
8. Supply Currents are measured for PLL-Bypass Mode (S2=1, S1=0)
3.3V Zero Delay Buffer
Notice: The information in this document is subject to change without notice.
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