DATASHEET
LOW SKEW 1 TO 4 CLOCK BUFFER
Description
The ICS556-04 is a low-skew, crystal input compatible
clock buffer with oscillator. This device offers the lowest
skew.
See the ICS552-02 for a 1-to-8 low skew buffer. For
more than eight outputs see the MK74CBxxx Buffalo
TM
series of clock drivers.
IDT makes many non-PLL and PLL-based low-skew
output devices. Contact IDT for all of your clocking
needs.
ICS556-04
Features
•
•
•
•
•
•
Extremely low-skew outputs (50 ps maximum)
Packaged in 8-pin SOIC
Operating voltages of 2.5 to 5.0 V
Low-power CMOS technology
Industrial temperature range
Available in Pb (lead) free package
NOTE: EOL for non-green parts to occur on
5/13/10 per PDN U-09-01
Block Diagram
Q0
5 to 27 MHz
Crystal or clock
X1/ICLK
Q1
Crystal
Oscillator/
Buffer
Q2
Q3
X2
Optional crystal
capacitors
IDT™ / ICS™
LOW SKEW 1 TO 4 CLOCK BUFFER
1
ICS556-04
REV D 092409
ICS556-04
LOW SKEW 1 TO 4 CLOCK BUFFER
CRYSTAL BUFFER
Pin Assignment
VDD
X 1 / I CL K
X2
GN D
1
2
3
4
8
7
6
5
Q4
Q3
Q2
Q1
8 - p i n ( 1 5 0 mi l ) S OI C
Pin Descriptions
Pin
Number
1
2
3
4
5
6
7
8
Pin
Name
VDD
X1/ICLK
X2
GND
Q1
Q2
Q3
Q4
Pin
Type
Power
Input
Input
Power
Output
Output
Output
Output
Pin Description
Connect to +2.5 V, +3.3 V or +5.0 V.
Crystal or clock input (5 V tolerant input). Connect to 5 to 27 MHz input.
Connect to a fundamental mode crystal. Leave open for clock input.
Connect to ground.
Clock Output 1.
Clock Output 2.
Clock Output 3.
Clock Output 3.
External Components
A minimum number of external components are required for proper operation. A decoupling capacitor of 0.01
µF
should be connected between VDD on pin 1 and GND on pin 4, as close to the device as possible. A 33Ω series
terminating resistor may be used on each clock output if the trace is longer than 1 inch.
To achieve the low output skew that the ICS556-04 is capable of, careful attention must be paid to board layout.
Essentially, all four outputs must have identical terminations, identical loads, and identical trace geometries. If not,
the output skew will be degraded. For example, using a 30Ω series termination on one output (with 33Ω on the
others) will cause at least 15 ps of skew.
Crystal Information
The crystal used should be a fundamental mode (do not use third overtone), parallel resonant. Crystal capacitors
should be connected from pins X1 to ground and X2 to ground to optimize the initial accuracy. The value of these
capacitors is given by the following equation:
Crystal caps (pF) = (CL - 6) x 2
In the equation, CL is the crystal load capacitance. So, for a crystal with a 16 pF load capacitance, two 20 pF [(16-6)
x 2] capacitors should be used.
IDT™ / ICS™
LOW SKEW 1 TO 4 CLOCK BUFFER
2
ICS556-04
REV D 092409
ICS556-04
LOW SKEW 1 TO 4 CLOCK BUFFER
CRYSTAL BUFFER
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS556-04. These ratings,
which are standard values for IDT commercially rated parts, are stress ratings only. Functional operation of
the device at these or any other conditions above those indicated in the operational sections of the
specifications is not implied. Exposure to absolute maximum rating conditions for extended periods can
affect product reliability. Electrical parameters are guaranteed only over the recommended operating
temperature range.
Item
Supply Voltage, VDD
Output Enable and All Outputs
ICLK
Ambient Operating Temperature
Storage Temperature
Junction Temperature
Soldering Temperature
7V
Rating
-0.5 V to VDD+0.5 V
-0.5 V to 5.5 V
-40 to +85
°
C
-65 to +150° C
125° C
260° C
Recommended Operation Conditions
Parameter
Ambient Operating Temperature
Power Supply Voltage (measured in respect to GND)
Min.
-40
+2.375
Typ.
Max.
+85
+5.25
Units
°
C
V
DC Electrical Characteristics
VDD=2.5 V ±5%,
Ambient temperature -40 to +85
°
C, unless stated otherwise
Parameter
Operating Voltage
Input High Voltage
Input Low Voltage
Output High Voltage
Output Low Voltage
Operating Supply Current
Nominal Output Impedance
Short Circuit Current
Symbol
VDD
V
IH
V
IL
V
OH
V
OL
IDD
Z
O
I
OS
Conditions
Min.
2.375
2.0
Typ.
Max.
2.625
0.8
Units
V
V
V
V
V
mA
Ω
mA
I
OH
= -12 mA
I
OL
= 12 mA
No load, 27MHz
2
0.4
25
20
±28
IDT™ / ICS™
LOW SKEW 1 TO 4 CLOCK BUFFER
3
ICS556-04
REV D 092409
ICS556-04
LOW SKEW 1 TO 4 CLOCK BUFFER
CRYSTAL BUFFER
DC Electrical Characteristics (continued)
VDD=3.3 V ±5%
, Ambient temperature -40 to +85
°
C, unless stated otherwise
Parameter
Operating Voltage
Input High Voltage
Input Low Voltage
Output High Voltage
Output Low Voltage
Output High Voltage (CMOS
Level)
Operating Supply Current
Nominal Output Impedance
Short Circuit Current
Symbol
VDD
V
IH
V
IL
V
OH
V
OL
V
OH
IDD
Z
O
I
OS
Conditions
Min.
3.15
2.0
Typ.
Max.
3.45
0.8
Units
V
V
V
V
V
V
I
OH
= -25 mA
I
OL
= 25 mA
I
OH
= -12 mA
No load, 27 MHz
2.4
0.4
VDD-0.4
35
20
±50
mA
Ω
mA
VDD=5 V ±5%
, Ambient temperature -40 to +85
°
C, unless stated otherwise
Parameter
Operating Voltage
Input High Voltage
Input Low Voltage
Output High Voltage
Output Low Voltage
Output High Voltage (CMOS
Level)
Operating Supply Current
Nominal Output Impedance
Short Circuit Current
Symbol
VDD
V
IH
V
IL
V
OH
V
OL
V
OH
IDD
Z
O
I
OS
Conditions
Min.
4.75
2.0
Typ.
Max.
5.25
0.8
Units
V
V
V
V
V
V
I
OH
= -35 mA
I
OL
= 35 mA
I
OH
= -12 mA
No load, 27 MHz
2.4
0.4
VDD-0.4
45
20
±80
mA
Ω
mA
Notes:
1. Nominal switching threshold is VDD/2
IDT™ / ICS™
LOW SKEW 1 TO 4 CLOCK BUFFER
4
ICS556-04
REV D 092409
ICS556-04
LOW SKEW 1 TO 4 CLOCK BUFFER
CRYSTAL BUFFER
AC Electrical Characteristics
VDD = 2.5 V ±5%,
Ambient Temperature -40 to +85
°
C, unless stated otherwise
Parameter
Input Frequency
Output Rise Time
Output Fall Time
Output to output skew
Duty Cycle
Symbol
t
OR
t
OF
Note 1
Conditions
0.8 to 2.0 V, C
L
=15 pF
2.0 to 0.8 V, C
L
=15 pF
Rising edges at VDD/2
Measured at VDD/2
Min.
5
Typ.
1.8
1.8
0
Max. Units
27
2.5
2.5
50
55
MHz
ns
ns
ps
%
45
50
VDD = 3.3 V ±5%,
Ambient Temperature -40 to +85
°
C, unless stated otherwise
Parameter
Input Frequency
Output Rise Time
Output Fall Time
Output to output skew
Duty Cycle
Phase Noise at 1MHz from
carrier
Clock Jitter RMS 1KHz to 1MHz
Symbol
t
OR
t
OF
Note 1
Conditions
0.8 to 2.0 V, C
L
=15 pF
2.0 to 0.8 V, C
L
=15 pF
Rising edges at VDD/2
Measured at VDD/2
Min.
5
Typ.
0.6
0.6
0
Max. Units
27
1.0
1.0
50
55
MHz
ns
ns
ps
%
dBc/Hz
6
ps
45
50
-125
VDD = 5 V ±5%,
Ambient Temperature -40 to +85
°
C, unless stated otherwise
Parameter
Input Frequency
Output Rise Time
Output Fall Time
Output to output skew
Duty Cycle
Symbol
t
OR
t
OF
Note 1
Conditions
0.8 to 2.0 V, C
L
=15 pF
2.0 to 0.8 V, C
L
=15 pF
Rising edges at VDD/2
Measured at VDD/2
Min.
5
Typ.
0.3
0.3
0
Max. Units
27
0.7
0.7
50
55
MHz
ns
ns
ps
%
45
50
Notes: 1. Between any two outputs with equal loading.
Thermal Characteristics
Parameter
Thermal Resistance Junction to
Ambient
Symbol
θ
JA
θ
JA
θ
JA
θ
JC
Conditions
Still air
1 m/s air flow
3 m/s air flow
Min.
Typ.
150
140
120
40
Max. Units
°
C/W
°
C/W
°
C/W
°
C/W
Thermal Resistance Junction to Case
IDT™ / ICS™
LOW SKEW 1 TO 4 CLOCK BUFFER
5
ICS556-04
REV D 092409
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