• Phase-Lock Loop Clock Distribution for Applications ranging
from 10MHz to 133MHz operating frequency
• Distributes one clock input to two banks of four outputs
• Separate output enable for each output bank
• External feedback (FBK) pin is used to synchronize the outputs
to the clock input
• Output Skew <200 ps
• Low jitter <200 ps cycle-to-cycle
• 1x, 2x, 4x output options (see table):
– IDT2308B-1 1x
– IDT2308B-2 1x, 2x
– IDT2308B-3 2x, 4x
– IDT2308B-4 2x
– IDT2308B-1H, -2H, and -5H for High Drive
• No external RC network required
• Operates at 3.3V V
DD
• Available in SOIC and TSSOP packages
IDT2308B
ADVANCE
INFORMATION
DESCRIPTION:
The IDT2308B is a high-speed phase-lock loop (PLL) clock multiplier. It is
designed to address high-speed clock distribution and multiplication applica-
tions. The zero delay is achieved by aligning the phase between the incoming
clock and the output clock, operable within the range of 10 to 133MHz.
The IDT2308B has two banks of four outputs each that are controlled via two
select addresses. By proper selection of input addresses, both banks can be
put in tri-state mode. In test mode, the PLL is turned off, and the input clock
directly drives the outputs for system testing purposes. In the absence of an
input clock, the IDT2308B enters power down, and the outputs are tri-stated.
In this mode, the device will draw less than 25µA.
The IDT2308B is available in six unique configurations for both pre-
scaling and multiplication of the Input REF Clock. (See available options
table.)
The PLL is closed externally to provide more flexibility by allowing the user
to control the delay between the input clock and the outputs.
The IDT2308B is characterized for both Industrial and Commercial opera-
tion.
NOTE:
For new designs, refer to AN-233.
FUNCTIONAL BLOCK DIAGRAM
(-3, -4)
FBK
REF
16
1
2
(-5)
2
PLL
3
2
CLKA1
CLKA2
14
CLKA3
15
CLKA4
S2
S1
8
9
Control
Logic
(-2, -3)
2
6
CLKB1
7
CLKB2
10
CLKB3
11
CLKB4
The IDT logo is a registered trademark of Integrated Device Technology, Inc.
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
1
c
2005
Integrated Device Technology, Inc.
OCTOBER 2005
DSC 6995/2
IDT2308B
3.3V ZERO DELAY CLOCK MULTIPLIER
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
(1)
Symbol
V
DD
Rating
Supply Voltage Range
Input Voltage Range (REF)
Input Voltage Range
(except REF)
I
IK
(V
I
< 0)
I
OK
(V
O
< 0 or V
O
> V
DD
)
I
O
(V
O
= 0 to V
DD
)
V
DD
or GND
Continuous Current
Maximum Power Dissipation
Storage Temperature Range
Commercial Temperature
Range
Industrial Temperature
Range
-40 to +85
°C
±100
0.7
–65 to +150
0 to +70
mA
W
°C
°C
T
A
= 55°C
(in still air)
(3)
T
STG
Operating
Temperature
Operating
Temperature
Input Clamp Current
Terminal Voltage with Respect
to GND (inputs V
IH
2.5, V
IL
2.5)
Continuous Output Current
±50
mA
Max.
–0.5 to +4.6
–0.5 to +5.5
–0.5 to
V
DD
+0.5
–50
±50
mA
mA
Unit
V
V
V
V
I (2)
V
I
REF
CLKA1
CLKA2
V
DD
GND
CLKB1
CLKB2
S2
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
FBK
CLKA4
CLKA3
V
DD
GND
CLKB4
CLKB3
S1
SOIC/ TSSOP
TOP VIEW
PIN DESCRIPTION
Pin Number
REF
(1)
CLKA1
(2)
CLKA2
(2)
V
DD
GND
CLKB1
(2)
CLKB2
(2)
S2
(3)
Functional Description
Input Reference Clock, 5 Volt Tolerant Input
Clock Output for Bank A
Clock Output for Bank A
3.3V Supply
Ground
Clock Output for Bank B
Clock Output for Bank B
Select Input, Bit 2
Select Input, Bit 1
Clock Output for Bank B
Clock Output for Bank B
Ground
3.3V Supply
Clock Output for Bank A
Clock Output for Bank A
PLL Feedback Input
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NOTES:
1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may
cause permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the
operational sections of this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect reliability.
2. The input and output negative-voltage ratings may be exceeded if the input and output
clamp-current ratings are observed.
3. The maximum package power dissipation is calculated using a junction temperature
of 150
°
C and a board trace length of 750 mils.
APPLICATIONS:
•
•
•
•
•
SDRAM
Telecom
Datacom
PC Motherboards/Workstations
Critical Path Delay Designs
S1
(3)
CLKB3
(2)
CLKB4
(2)
GND
V
DD
CLKA3
(2)
CLKA4
(2)
FBK
NOTES:
1. Weak pull down.
2. Weak pull down on all outputs.
3. Weak pull ups on these inputs.
2
IDT2308B
3.3V ZERO DELAY CLOCK MULTIPLIER
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
FUNCTION TABLE
(1)
SELECT INPUT DECODING
S2
L
L
H
H
NOTE:
1. H = HIGH Voltage Level
L = LOW Voltage Level
S1
L
H
L
H
CLK A
Tri-State
Driven
Driven
Driven
CLK B
Tri-State
Tri-State
Driven
Driven
Output Source
PLL
PLL
REF
PLL
PLL Shut Down
Y
N
Y
N
AVAILABLE OPTIONS FOR IDT2308B
Device
IDT2308B-1
IDT2308B-1H
IDT2308B-2
IDT2308B-2
IDT2308B-2H
IDT2308B-2H
IDT2308B-3
IDT2308B-3
IDT2308B-4
IDT2308B-5H
Feedback From
Bank A or Bank B
Bank A or Bank B
Bank A
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
Reference
2 x Reference
2 x Reference
4 x Reference
2 x Reference
Reference/2
Bank B Frequency
Reference
Reference
Reference/2
Reference
Reference/2
Reference
Reference or
Reference
(1)
2 x Reference
2 x Reference
Reference/2
NOTE:
1. Output phase is indeterminant (0° or 180° from input clock).
3
IDT2308B
3.3V ZERO DELAY CLOCK MULTIPLIER
COMMERCIAL AND INDUSTRIAL TEMPERATURE RANGES
ZERO DELAY AND SKEW CONTROL
To close the feedback loop of the IDT2308B, 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.
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 Output Load Difference Chart to calculate loading differences between the feedback output and remaining outputs.
Ensure the outputs are loaded equally, for zero output-output skew.
REF TO CLKA/CLKB DELAY vs. OUTPUT LOAD DIFFERENCE BETWEEN FBK PIN AND CLKA/CLKB PINS
1500
1000
REF to CLKA/CLKB Delay (ps)
500
0
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
-500
-1000
-1500
OUTPUT LOAD DIFFERENCE BETWEEN FBK PIN AND CLKA/CLKB PINS ( pF)
能源基础设施
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