ICS680-01
MDS 680-01 F 1Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
Networking Clock Synthesizer and Zero Delay Buffer
Description
The ICS680-01 generates four high-frequency clock
outputs and a reference from a 25 MHz crystal or clock
input. The device includes a low-skew, single input to
four output zero delay clock buffer. It can replace
multiple crystals and oscillators, saving board space
and cost.
The device has a power-down tri-state (PDTS) pin that
place the clock outputs in a high-impedance state when
pulled low. The PDTS pin includes an internal pull-up
resistor.
Features
•Packaged in 24-pin TSSOP
•Available in Pb (lead) free package
•Replaces multiple crystals and oscillators
•Input crystal or clock frequency of 25 MHz
•Five output driver driven by external clock
•Duty cycle of 45/55
•Operating voltage of 3.3 V
•Advanced, low-power CMOS process
•Fixed output frequencies of 25 MHz and 48 MHz
•Selectable output frequencies of 24 MHz, 48 MHz,
50 MHz and 66.6666 MHz
•Qx outputs replace costly discrete buffer
•Low-skew buffer outputs (250 ps)
Block Diagram
Divide
Logic
and
Output
Enable
Control
External capacitors
may be required.
S0
VDD
CLK2
CLK1
48M
25M
Q0
5
Q2
Q3
GND PDTS
2
X1/ICLK
X2
Crystal
Oscillator
25 MHz
Crystal or Clock
PLLA
PLLB
Q1
ICLK
S1
PLL/Buffer
PLLC
QFB
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 2Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
Pin Assignment Output Clock Select Table
Pin Descriptions
13
4
5CLK1
8
9
10
25M
Q1 QFB
48M
Q2 VDD
17
16
VDD
3S0
VDD S1
18
PDTS
1X1/ICLK
GND VDD
20
X2
19
14
2
7
GND
GND
ICLK
VDD
15
6
24-pin TSSOP
11
12 GND
Q3 CLK2
Q4
21
22
23
24 S0 S1 CLK1 (MHz) CLK2 (MHz)
MM OFF 48
0 0 50 48
0 1 66.6666 48
1 0 50 24
1 1 66.6666 24
Pin
Number
Pin
Name
Pin
Type
Pin Description
1 X1/ICLK XI Crystal input. Connect this pin to a crystal or external clock source.
2 GND Power Connect to ground.
3 S0 Input Select pin 0. See table above.
4 VDD Power Connect to voltage supply.
5 CLK1 Output Selectable output clock. See table above. Weak internal pull-down when
tri-state.
6 GND Power Connect to ground.
7 GND Power Connect to ground.
8 Q1 Output Clock output 1. Weak internal pull-down when tri-state.
9 Q2 Output Clock output 2. Weak internal pull-down when tri-state.
10 VDD Power Connect to voltage supply.
11 Q3 Output Clock output 3. Weak internal pull-down when tri-state.
12 Q4 Output Clock output 4. Weak internal pull-down when tri-state.
13 GND Power Connect to ground.
14 CLK2 Output Selectable output clock. See table above. Weak internal pull-down when
tri-state.
15 48M Output 48 MHz output clock. Weak internal pull-down when tri-state.
16 VDD Power Connect to voltage supply.
17 QFB Output Feedback pin. Internally connected.
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 3Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
External Components
The ICS680-01 requires a minimum number of external
components for proper operation.
Decoupling Capacitor
A decoupling capacitor of 0.01µF must be connected
between VDD (pins 5 and 16) and GND (pins 6 and
15), as close to these pins as possible. For optimum
device performance, the decoupling capacitor should
be mounted on the component side of the PCB. Avoid
the use of vias in the decoupling circuit.
Series Termination Resistor
When the PCB trace between the clock outputs and the
loads are over 1 inch, series termination should be
used. To series terminate a 50Ω trace (a commonly
used trace impedance) place a 33Ω resistor in series
with the clock line, as close to the clock output pin as
possible. The nominal impedance of the clock output is
20Ω.
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)x2
In the equation, CL is the crystal load capacitance. So
for a crystal with a 16 pF load capacitance, two 20
pF[(16-6)x2] capacitors should be used
PCB Layout Recommendations
For optimum device performance and lowest output
phase noise, the following guidelines should be
observed.
1) The 0.01µF decoupling capacitor should be mounted
on the component side of the board as close to the
VDD pin as possible. No vias should be used between
decoupling capacitor and VDD pin. The PCB trace to
VDD pin should be kept as short as possible, as should
the PCB trace to the ground via.
2) The external crystal should be mounted just next to
the device with short traces. The X1 and X2 traces
should not be routed next to each other with minimum
spaces, instead they should be separated and away
from other traces.
3) To minimize EMI, the 33Ω series termination resistor
(if needed) should be placed close to the clock output.
4) An optimum layout is one with all components on the
same side of the board, minimizing vias through other
signal layers. Other signal traces should be routed
away from the ICS680-01. This includes signal traces
just underneath the device, or on layers adjacent to the
ground plane layer used by the device.
18 VDD Power Connect to voltage supply.
19 ICLK Input Zero Delay Buffer Input. Weak Internal pull-up.
20 25M Output 25 MHz reference output clock. Weak internal pull-down when tri-state.
21 S1 Input Select pin 1. See table above.
22 PDTS Power Power-down tri-state. Powers down entire chip and tri-states outputs
when low. Internal pull-up resistor.
23 VDD Power Connect to voltage supply.
24 X2 XO Crystal output. Connect this pin to a crystal. Float for clock input.
Pin
Number
Pin
Name
Pin
Type
Pin Description
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 4Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
Absolute Maximum Ratings
Stresses above the ratings listed below can cause permanent damage to the ICS680-01. These ratings,
which are standard values for ICS 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.
Recommended Operation Conditions
Item Rating
Supply Voltage, VDD 7 V
All Inputs and Outputs -0.5 V to VDD+0.5 V
Ambient Operating Temperature 0 to +70°C
Storage Temperature -65 to +150°C
Junction Temperature 125°C
Soldering Temperature 260°C
Parameter Min. Typ. Max. Units
Ambient Operating Temperature 0 +70 °C
Power Supply Voltage (measured in respect to GND) +3.13 +3.3 +3.46 V
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 5Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
DC Electrical Characteristics
Unless stated otherwise, VDD = 3.3 V ±5%, Ambient Temperature 0 to +70°C
Parameter Symbol Conditions Min. Typ. Max. Units
Operating Voltage VDD 3.13 3.3 3.46 V
Supply Current IDD No load,PDTS=1 32 mA
No load,PDTS=0 300 µA
Input High Voltage, binary
inputs
VIH PDTS, ICLK 2 V
Input High Voltage, trinary
inputs
VIH S0, S1 VDD-0.5 V
Input Low Voltage, binary
inputs
VIL PDTS, ICLK 0.8 V
Input Low Voltage, trinary
inputs
VIL S0, S1 0.5 V
Output High Voltage VOH IOH = -4 mA VDD-0.4 V
Output High Voltage VOH IOH = -12 mA 2.4 V
Output Low Voltage VOL IOL = 12 mA 0.8 V
IOL = 4 mA 0.4 V
Short Circuit Current IOS CLK output ±50 mA
Input Capacitance, Inputs CIN 5pF
Nominal Output
Impedance
ZOUT 20 Ω
On-Chip Pull-up Resistor,
Inputs
RPU PDTS, SEL 250 kΩ
On-Chip Pull-down
Resistor, Outputs
RPD CLK outputs 250 kΩ
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 6Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
AC Electrical Characteristics
Unless stated otherwise, VDD = 3.3 V ±5%, Ambient Temperature 0 to +70° C
Note 1: Measured with a 15 pF load.
Note 2: Duty cycle is configuration dependent. Most configurations are min 45% / max 55%.
Note 3: Skew is measured at 1.4 V on rising edges with a 33 MHz ICLK.
Parameter Symbol Conditions Min. Typ. Max. Units
Input Frequency fIN X1 25 MHz
ICLK 33 MHz
Output Frequency fOUT Q0 to Q3, QFB, Note 1 33 MHz
Output Rise Time tOR 20% to 80%, Note 1 1.5 ns
Output Fall Time tOF 80% to 20%, Note 1 1.5 ns
Output Clock Duty Cycle tDat VDD/2, Note 2 40 60 %
Power-up Time PLL lock-time from
power-up to 1% of final
frequency
10 ms
PDTS goes high until
stable CLK outputs at
1% of final frequency
2ms
One Sigma Clock Period Jitter Configuration
dependent
50 ps
Maximum Absolute Jitter tja Deviation from mean.
Configuration
dependent.
±200 ps
QFB to ICLK Skew tPD Measured at VDD/2,
Note 3
-350 350
Pin-to-pin Skew QFB, Q0 to Q3, Note 3 -250 250 ps
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 7Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
Package Outline and Package Dimensions (24-pin TSSOP, 173 Mil. Body)
Package dimensions are kept current with JEDEC Publication No. 95
Ordering Information
“LF” denotes Pb (lead) free package.
While the information presented herein has been checked for both accuracy and reliability, Integrated Circuit Systems (ICS)
assumes no responsibility for either its use or for the infringement of any patents or other rights of third parties, which would
result from its use. No other circuits, patents, or licenses are implied. This product is intended for use in normal commercial
applications. Any other applications such as those requiring extended temperature range, high reliability, or other extraordinary
environmental requirements are not recommended without additional processing by ICS. ICS reserves the right to change any
circuitry or specifications without notice. ICS does not authorize or warrant any ICS product for use in life support devices or
critical medical instruments.
Part / Order Number Marking Shipping Packaging Package Temperature
ICS680G-01 680G-01 Tubes 24-pin TSSOP 0 to +70° C
ICS680G-01T 680G-01 Tape and Reel 24-pin TSSOP 0 to +70° C
ICS680G-01LF 680G-01LF Tubes 24-pin TSSOP 0 to +70° C
ICS680G-01LFT 680G-01LF Tape and Reel 24-pin TSSOP 0 to +70° C
INDEX
AREA
1 2
24
D
E1 E
SEATING
PLANE
A1
A
A2
e
- C -
b
.10 (.004) C
c
L
Millimeters Inches
Symbol Min Max Min Max
A — 1.20 — .047
A1 0.05 0.15 0.002 0.006
A2 0.80 1.05 0.032 0.041
b 0.19 0.30 0.007 0.012
C 0.09 0.20 0.0035 0.008
D 7.70 7.90 0.303 0.311
E 6.40 BASIC 0.252 BASIC
E1 4.30 4.50 0.169 0.177
e 0.65 Basic 0.0256 Basic
L 0.450.75.018.030
α0°8°0°8°
Networking Clock Synthesizer and Zero Delay Buffer
MDS 680-01 F 8Revision 020305
Integrated Circuit Systems, Inc. ● 525 Race Street, San Jose, CA 95126 ● tel (408) 297-1201 ● www.icst.com
ICS680-01
Revision History
Rev. Originator Date Description of Change
D P.Griffith 10/01/04 Removed power supply ramp-up time spec; added trinary input specs to DC chars; added
a second Output Low Voltage spec; updated Supply Current specs from 50 to 32 mA, and
50 to 300 uA; changed pull-down resistor value from 525 to 250 kohms; changed Output
Rise/Fall times from 1 to 1.5 ns
E P.Griffith 12/21/04 Released as standard product from custom device.
F J. Sarma 02/03/05 Add LF ordering info.
