19-2697; Rev 0; 12/02
Low-Jitter 155MHz/622MHz Clock Generator
General Description
The MAX3672 is a low-jitter 155MHz/622MHz reference
clock generator IC designed for system clock distribution
and frequency synchronization in OC-48 and OC-192
SONET/SDH and WDM transmission systems. The
MAX3672 integrates a phase/frequency detector, an
operational amplifier (op amp), prescaler dividers, and
input/output buffers. Using an external VCO, the
MAX3672 can be configured easily as a phase-lock loop
with bandwidth programmable from 30Hz to 10kHz.
The MAX3672 operates from a single +3.3V or +5.0V
supply and dissipates 150mW (typ) at 3.3V. The operat-
ing temperature range is -40°C to +85°C.
Features
o
Single +3.3V or +5.0V Supply
o
Power Dissipation: 150mW at +3.3V Supply
o
External VCO Center Frequencies (f
VCO
): 155MHz
to 700MHz
o
Reference Clock Frequencies: f
VCO
, f
VCO
/2,
f
VCO
/4, f
VCO
/8, f
VCO
/32
o
Main Clock Output Frequency: f
VCO
o
Optional Output Clock Frequencies: f
VCO
, f
VCO
/2,
f
VCO
/4, f
VCO
/8
o
Low Intrinsic Jitter: <0.4ps
RMS
o
Loss-of-Lock Indicator
o
PECL Clock Output Interface
MAX3672
Applications
OC-12 to OC-192 SONET/WDM Transport
Systems
Clock Jitter Clean-Up and Frequency
Synchronization
Frequency Conversion
System Clock Distribution
Ordering Information
PART
MAX3672E/D
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
Dice*
*Dice
are designed to operate from -40° to +85°C, but are test-
ed and guaranteed at T
A
= +25° only.
Typical Application Circuit
+3.3V
142Ω
155MHz
REFCLK+
+3.3V
142Ω
REFCLK-
VCOIN+
VCO
K
VCO
= 25kHz/V
155MHz
100Ω
VCOIN-
142Ω
VCCD
MOUT+
MOUT-
142Ω
MAX3892
16:1
SERIALIZER
MAX3672
RSEL
VSEL
NSEL1
N.C.
N.C.
332Ω
VC
0.01µF
4700pF
500kΩ
OPAMP-
OPAMP+
4700pF
REPRESENTS A
CONTROLLED-IMPEDANCE
TRANSMISSION LINE.
500kΩ
VFILTER
1000pF
POLAR
GND
3.3V
SETUP FOR 10kHz LOOP
BANDWIDTH
GSEL
NSEL2
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Low-Jitter 155MHz/622MHz Clock Generator
MAX3672
ABSOLUTE MAXIMUM RATINGS
Supply Voltage ......................................................-0.5V to +7.0V
Voltage at C2+, C2-, THADJ, CTH, NSEL1, NSEL2, GSEL,
LOL,
RSEL, REFCLK-, REFCLK+, VSEL, VCOIN+, VCOIN-, VC,
POLAR, PSEL1, PSEL2, COMP,
OPAMP+, OPAMP- ..................................-0.5V to (V
CC
+ 0.5V)
Voltage at V
FILTER
.................................................-0.5V to +3.0V
PECL Output Current (MOUT+,
MOUT-, POUT+, POUT-).................................................56mA
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range. ............................-65°C to +160°C
Die-Attach Process Temperature.....................................+400°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±10% or V
CC
= +5.0V ±10%, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless other-
wise noted.) (Note 1)
PARAMETER
Supply Current
SYMBOL
I
CC
(Note 2)
CONDITIONS
MIN
TYP
50
MAX
72
UNITS
mA
INPUT SPECIFICATIONS
(REFCLK±, VCOIN±)
Input High Voltage
Input Low Voltage
V
IH
V
IL
V
CC
-
1.16
V
CC
-
1.81
V
CC
-
1.3
7.2
12.0
AC-coupled
300
V
CC
-
1.025
V
CC
-
1.085
V
CC
-
1.81
V
CC
-
1.83
2.4
11.5
21.0
17.5
32.5
1900
V
CC
-
0.88
V
-40°C to 0°C
0°C to +85°C
Output Low Voltage
V
OL
-40°C to 0°C
TTL SPECIFICATIONS
Output High Voltage
Output Low Voltage
V
OH
V
OL
Sourcing 20µA
Sinking 2mA
V
CC
0.4
V
V
V
CC
-
0.88
V
CC
-
1.62
V
CC
-
1.556
V
V
CC
-
0.88
V
CC
-
1.48
V
V
Input Bias Voltage
Common-Mode Input Resistance
Differential Input Resistance
Differential Input Voltage Swing
PECL OUTPUT SPECIFICATIONS
0°C to +85°C
Output High Voltage
V
OH
V
kΩ
kΩ
mV
P-P
2
_______________________________________________________________________________________
Low-Jitter 155MHz/622MHz Clock Generator
DC ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.3V ±10% or V
CC
= +5.0V ±10%, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless other-
wise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
V
CC
-
0.3
V
CC
-
0.5
3
90
High gain
Low gain
High gain
Low gain
16.0
4.0
20
5
24.4
6.2
0.80
1.08
V
UNITS
MAX3672
OPERATIONAL AMPLIFIER SPECIFICATIONS
(Note 3)
V
CC
= +3.3V ±10%
Op Amp Output Voltage Range
V
O
V
CC
= +5.0V ±10%
Op Amp Input Offset Voltage
Op Amp Open-Loop Gain
Full-Scale PFD/CP Output
Current
PFD/CP Offset Current
| V
OS
|
A
OL
0.5
0.3
mV
dB
PHASE FREQUENCY DETECTOR (PFD)/CHARGE-PUMP (CP) SPECIFICATIONS
(Note 4)
| I
PD
|
µA
%
| I
PD
|
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±10% or V
CC
= +5.0V ±10%, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless other-
wise noted.) (Note 5)
PARAMETER
Clock Output Frequency
Optional Clock Output
Frequency
Clock Output Rise/Fall Time
Clock Output Duty Cycle
NOISE SPECIFICATIONS
Random Noise Voltage at Loop-
Filter Output
Spurious Noise Voltage at Loop-
Filter Output
Power-Supply Rejection at Loop-
Filter Output
PSR
V
NOISE
Freq > 1kHz (Note 7)
(Note 8)
(Note 9)
30
50
1.14
µV
RMS
/√Hz
µV
RMS
dB
f
VCO
= 622MHz
f
VCO
= 155MHz
Measured from 20% to 80%
(Note 6)
45
622/311/
155/78
155/78/
38/19
280
55
SYMBOL
CONDITIONS
MIN
TYP
MAX
700
UNITS
MHz
CLOCK OUTPUT SPECIFICATIONS
MHz
ps
%
REFERENCE CLOCK INPUT SPECIFICATIONS
Reference Clock Frequency
Reference Clock Duty Cycle
30
622/
155/78/
19
700
70
MHz
%
_______________________________________________________________________________________
3
Low-Jitter 155MHz/622MHz Clock Generator
MAX3672
AC ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.3V ±10% or V
CC
= +5.0V ±10%, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V and T
A
= +25°C, unless other-
wise noted.) (Note 5)
PARAMETER
PLL SPECIFICATIONS
PLL Jitter Transfer Bandwidth
Jitter Transfer Peaking
OPAMP SPECIFICATION
Unity-Gain Bandwidth
VCO INPUT SPECIFICATIONS
VCO Input Frequency
VCO Input Slew Rate
f
VCO
0.5
622/155
700
MHz
V/ns
7
MHz
BW
(Note 10)
F
JITTER
≤
BW (Note 11)
30
10,000
0.1
Hz
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Specifications at -40°C are guaranteed by design and characterization.
Measured with PECL outputs unterminated.
OPAMP specifications met with 10kΩ load to ground or 5kΩ load to V
CC
(POLAR = 0 and POLAR = V
CC
).
PFD/CP currents are measured from pins OPAMP+ to OPAMP-. See Table 4 for gain settings.
AC characteristics are guaranteed by design and characterization.
Measured with 50% VCO input duty cycle.
Random noise voltage at op amp output with 800kΩ resistor connected between VC and OPAMP-, PFD/CP gain (K
PD
) =
5µA/UI, and POLAR = 0. Measured with the PLL open loop and no REFCLK or VCO input.
Note 8:
Spurious noise voltage due to PFD/CP output pulses measured at op amp output with R
1
= 800kΩ, K
PD
= 5µA/UI, and com-
pare frequency 400 times greater than the higher-order pole frequency (see the
Design Procedure
section).
Note 9:
PSR measured with a 100mV
P-P
sine wave on V
CC
in a frequency range from 100Hz to 2MHz. External resistors R
1
matched
to within 1%, external capacitors C
1
matched to within 10%. Measured closed loop with PLL bandwidth set to 200Hz.
Note 10:
The PLL 3dB bandwidth is adjusted from 30Hz to 10kHz by changing external components R
1
and C
1
, by selecting the
internal programmable divider ratio and phase-detector gain. Measured with VCO gain of 150ppm/V and C
1
limited to 2.2µF.
Note 11:
When input jitter frequency is above PLL transfer bandwidth (BW), the jitter transfer function rolls off at -20dB/decade.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
4
_______________________________________________________________________________________
Low-Jitter 155MHz/622MHz Clock Generator
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
MAX3672
SUPPLY CURRENT
vs. TEMPERATURE
MAX3672 toc01
OUTPUT CLOCK EDGE SPEED
vs. TEMPERATURE
270
260
250
240
230
220
210
200
190
180
170
160
150
140
-40
MAX3672 toc02
POWER-SUPPLY REJECTION
vs. FREQUENCY
BW = 1kHz
-10
SUPPLY REJECTION (dB)
-20
-30
-40
-50
-60
LOOP FILTER OUTPUT
MAX3672 toc03
70
0
5.0V
50
3.3V
EDGE SPEED 20% TO 80% (ps)
60
SUPPLY CURRENT (mA)
40
155.52
667
30
20
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
-20
0
20
40
60
80
1k
10k
100k
FREQUENCY (Hz)
1M
10M
TEMPERATURE (°C)
667MHz CLOCK OUTPUT
MAX3672 toc04
155MHz CLOCK OUTPUT
MAX3672 toc05
200mV/div
200mV/div
500ps/div
2ns/div
_______________________________________________________________________________________
5
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