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.
Applications
OC-12 to OC-192 SONET/WDM Transport
Systems
Clock Jitter Clean-Up and Frequency
Synchronization
Frequency Conversion
System Clock Distribution
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
Low-Jitter 155MHz/622MHz Clock Generator
________________________________________________________________ Maxim Integrated Products
1
Ordering Information
MAX3672
155MHz
142
142
100
332
500k
500k
+3.3V
+3.3V
4700pF
4700pF
0.01
µF
SETUP FOR 10kHz LOOP
BANDWIDTH
3.3V
N.C.
N.C.
142
142
REFCLK+
REFCLK-
VCOIN+
VCOIN-
VC
OPAMP-
OPAMP+
POLAR
GND
MOUT+
MOUT-
RSEL
VSEL
NSEL1
NSEL2
GSEL
VCO
K
VCO
= 25kHz/V
155MHz
REPRESENTS A
CONTROLLED-IMPEDANCE
TRANSMISSION LINE.
VCCD
MAX3892
16:1
SERIALIZER
1000pF
VFILTER
Typical Application Circuit
19-2697; Rev 0; 12/02
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.
PART
TEMP RANGE
PIN-PACKAGE
MAX3672E/D
-40°C to +85°C
Dice*
*Dice are designed to operate from -40° to +85°C, but are test-
ed and guaranteed at T
A
= +25° only.
MAX3672
Low-Jitter 155MHz/622MHz Clock Generator
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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)
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.
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
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Current
I
CC
(Note 2)
50
72
mA
INPUT SPECIFICATIONS (REFCLK±, VCOIN±)
Input High Voltage
V
IH
V
CC
-
1.16
V
CC
-
0.88
V
Input Low Voltage
V
IL
V
CC
-
1.81
V
CC
-
1.48
V
Input Bias Voltage
V
CC
-
1.3
V
Common-Mode Input Resistance
7.2
11.5
17.5
k
Differential Input Resistance
12.0
21.0
32.5
k
Differential Input Voltage Swing
AC-coupled
300
1900
mV
P-P
PECL OUTPUT SPECIFICATIONS
0°C to +85°C
V
CC
-
1.025
V
CC
-
0.88
Output High Voltage
V
OH
-40°C to 0°C
V
CC
-
1.085
V
CC
-
0.88
V
0°C to +85°C
V
CC
-
1.81
V
CC
-
1.62
Output Low Voltage
V
OL
-40°C to 0°C
V
CC
-
1.83
V
CC
-
1.556
V
TTL SPECIFICATIONS
Output High Voltage
V
OH
Sourcing 20µA
2.4
V
CC
V
Output Low Voltage
V
OL
Sinking 2mA
0.4
V
MAX3672
Low-Jitter 155MHz/622MHz Clock Generator
_______________________________________________________________________________________
3
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
UNITS
OPERATIONAL AMPLIFIER SPECIFICATIONS (Note 3)
V
CC
= +3.3V ±10%
0.3
V
CC
-
0.3
Op Amp Output Voltage Range
V
O
V
CC
= +5.0V ±10%
0.5
V
CC
-
0.5
V
Op Amp Input Offset Voltage
| V
OS
|
3
mV
Op Amp Open-Loop Gain
A
OL
90
dB
PHASE FREQUENCY DETECTOR (PFD)/CHARGE-PUMP (CP) SPECIFICATIONS (Note 4)
High gain
16.0
20
24.4
Full-Scale PFD/CP Output
Current
| I
PD
|
Low gain
4.0
5
6.2
µA
High gain
0.80
PFD/CP Offset Current
Low gain
1.08
%
| 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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CLOCK OUTPUT SPECIFICATIONS
Clock Output Frequency
700
MHz
f
VCO
= 622MHz
622/311/
155/78
Optional Clock Output
Frequency
f
VCO
= 155MHz
155/78/
38/19
MHz
Clock Output Rise/Fall Time
Measured from 20% to 80%
280
ps
Clock Output Duty Cycle
(Note 6)
45
55
%
NOISE SPECIFICATIONS
Random Noise Voltage at Loop-
Filter Output
V
NOISE
Freq > 1kHz (Note 7)
1.14
µV
RMS
/
Hz
Spurious Noise Voltage at Loop-
Filter Output
(Note 8)
50
µV
RMS
Power-Supply Rejection at Loop-
Filter Output
PSR
(Note 9)
30
dB
REFERENCE CLOCK INPUT SPECIFICATIONS
Reference Clock Frequency
622/
155/78/
19
700
MHz
Reference Clock Duty Cycle
30
70
%
Note 1: Specifications at -40°C are guaranteed by design and characterization.
Note 2: Measured with PECL outputs unterminated.
Note 3: OPAMP specifications met with 10k
load to ground or 5k load to V
CC
(POLAR = 0 and POLAR = V
CC
).
Note 4: PFD/CP currents are measured from pins OPAMP+ to OPAMP-. See Table 4 for gain settings.
Note 5: AC characteristics are guaranteed by design and characterization.
Note 6: Measured with 50% VCO input duty cycle.
Note 7: Random noise voltage at op amp output with 800k
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
= 800k
, 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.
MAX3672
Low-Jitter 155MHz/622MHz Clock Generator
4
_______________________________________________________________________________________
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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
PLL SPECIFICATIONS
PLL Jitter Transfer Bandwidth
BW
(Note 10)
30
10,000
Hz
Jitter Transfer Peaking
F
JITTER
BW (Note 11)
0.1
dB
OPAMP SPECIFICATION
Unity-Gain Bandwidth
7
MHz
VCO INPUT SPECIFICATIONS
VCO Input Frequency
f
VCO
622/155
700
MHz
VCO Input Slew Rate
0.5
V/ns
MAX3672
Low-Jitter 155MHz/622MHz Clock Generator
_______________________________________________________________________________________
5
20
30
50
40
60
70
-40
0
-20
20
40
60
80
SUPPLY CURRENT
vs. TEMPERATURE
MAX3672 toc01
TEMPERATURE (
°C)
SUPPLY CURRENT (mA)
5.0V
3.3V
OUTPUT CLOCK EDGE SPEED
vs. TEMPERATURE
MAX3672 toc02
TEMPERATURE (
°C)
EDGE SPEED 20% TO 80% (ps)
80
60
20
40
0
-20
150
160
170
180
190
200
210
220
230
240
250
260
270
140
-40
155.52
667
0
-60
1k
100k
1M
10k
10M
POWER-SUPPLY REJECTION
vs. FREQUENCY
MAX3672 toc03
FREQUENCY (Hz)
SUPPLY REJECTION (dB)
-50
-40
-30
-20
-10
BW = 1kHz
LOOP FILTER OUTPUT
500ps/div
667MHz CLOCK OUTPUT
200mV/div
MAX3672 toc04
2ns/div
155MHz CLOCK OUTPUT
200mV/div
MAX3672 toc05
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
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