FemtoClock
®
Crystal-to-LVDS
Clock Generator
G
ENERAL
D
ESCRIPTION
The 844021I-01 is an Ethernet Clock Generator. The 844021I-01
uses an 18pF parallel resonant crystal over the range of 24.5MHz
– 34MHz. For Ethernet appli-cations, a 25MHz crystal is used. The
844021I-01 has excellent <1ps phase jitter performance, over the
1.875MHz – 20MHz integration range. The 844021I-01 is packaged
in a small 8-pin TSSOP, making it ideal for use in systems with
limited board space.
844021I-01
DATA SHEET
F
EATURES
•
One Differential LVDS output
•
Crystal oscillator interface, 18pF parallel resonant crystal
(24.5MHz
–
34MHz)
•
Output frequency range: 122.5MHz
–
170MHz
•
VCO range: 490MHz
–
680MHz
•
RMS phase jitter @ 125MHz, using a 25MHz crystal
(1.875MHz
–
20MHz): 0.32ps (typical) @ 3.3V
•
3.3V or 2.5V operating supply
•
-40°C to 85°C ambient operating temperature
•
Available in lead-free (RoHS 6) package
C
OMMON
C
ONFIGURATION
T
ABLE
- Gb E
THERNET
Inputs
Crystal Frequency (MHz)
25
26.666
33.33
M
20
20
20
N
4
4
4
Multiplication
Value M/N
5
5
5
Output Frequency
(MHz)
125
133.33
166.66
B
LOCK
D
IAGRAM
OE
Pullup
P
IN
A
SSIGNMENT
V
DDA
GND
XTAL_OUT
XTAL_IN
1
2
3
4
8
7
6
5
V
DD
Q
nQ
OE
XTAL_IN
OSC
XTAL_OUT
Phase
Detector
VCO
490MHz - 680MHz
N = ÷4
(fixed)
Q
nQ
844021I-01
8-Lead TSSOP
4.40mm x 3.0mm x 0.925mm
package body
G Package
Top View
M = ÷20
(fixed)
844021I-01 REVISION A 10/27/15
1
©2015 Integrated Device Technology, Inc.
844021I-01 DATA SHEET
T
ABLE
1. P
IN
D
ESCRIPTIONS
Number
1
2
3,
4
5
6, 7
8
Name
V
DDA
GND
XTAL_OUT,
XTAL_IN
OE
nQ, Q
V
DD
Power
Power
Input
Input
Output
Power
Pullup
Type
Description
Analog supply pin.
Power supply ground.
Crystal oscillator interface. XTAL_IN is the input,
XTAL_OUT is the output.
Output enable pin. When HIGH, Q/nQ output is active.
When LOW, the Q/nQ output is in a high impedance state. LVCMOS/LVT-
TL interface levels.
Differential clock outputs. LVDS interface levels.
Core supply pin.
NOTE:
Pullup
refers to internal input resistors. See Table 2, Pin Characteristics, for typical values.
T
ABLE
2. P
IN
C
HARACTERISTICS
Symbol
C
IN
R
PULLUP
Parameter
Input Capacitance
Input Pullup Resistor
Test Conditions
Minimum
Typical
4
51
Maximum
Units
pF
kΩ
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
CLOCK GENERATOR
2
REVISION A 10/27/15
844021I-01 DATA SHEET
A
BSOLUTE
M
AXIMUM
R
ATINGS
Supply Voltage, V
DD
Inputs, V
I
Outputs, I
O
(LVDS)
Continuous Current
Surge Current
Package Thermal Impedance,
θ
JA
Storage Temperature, T
STG
4.6V
-0.5V to V
DD
+ 0.5 V
10mA
15mA
129.5°C/W (0 mps)
-65°C to 150°C
N OT E : S t r e s s e s b eyo n d t h o s e l i s t e d u n d e r A b s o l u t e
Maximum Ratings may cause permanent damage to the
device. These ratings are stress specifications only. Function-
al operation of product at these conditions or any conditions
beyond those listed in the
DC Characteristics
or
AC Char-
acteristics
is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect product reliability.
T
ABLE
3A. P
OWER
S
UPPLY
DC C
HARACTERISTICS
,
V
DD
= 3.3V±5%, T
A
= -40°C
TO
85°C
Symbol
V
DD
V
DDA
I
DD
I
DDA
Parameter
Core Supply Voltage
Analog Supply Voltage
Power Supply Current
Analog Supply Current
Test Conditions
Minimum
3.135
V
DD
– 0.10
Typical
3.3
3.3
Maximum
3.465
V
DD
75
10
Units
V
V
mA
mA
T
ABLE
3B. P
OWER
S
UPPLY
DC C
HARACTERISTICS
,
V
DD
= 2.5V±5%, T
A
= -40°C
TO
85°C
Symbol
V
DD
V
DDA
I
DD
I
DDA
Parameter
Core Supply Voltage
Analog Supply Voltage
Power Supply Current
Analog Supply Current
Test Conditions
Minimum
2.375
V
DD
– 0.10
Typical
2.5
2.5
Maximum
2.625
V
DD
70
10
Units
V
V
mA
mA
T
ABLE
3C. LVCMOS/LVTTL DC C
HARACTERISTICS
,
V
DD
= 3.3V±5%
OR
2.5V±5%, T
A
= -40°C
TO
85°C
Symbol
V
IH
V
IL
I
IH
I
IL
Parameter
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
Test Conditions
V
DD
= 3.3V
V
DD
= 2.5V
V
DD
= 3.3V
V
DD
= 2.5V
V
DD
= V
IN
= 3.465V or 2.625V
V
DD
= 3.465V or 2.625V, V
IN
= 0V
-150
Minimum
2
1.7
-0.3
-0.3
Typical
Maximum
V
DD
+ 0.3
V
DD
+ 0.3
0.8
0.7
5
Units
V
V
V
V
µA
µA
REVISION A 10/27/15
3
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
CLOCK GENERATOR
844021I-01 DATA SHEET
T
ABLE
3D. LVDS DC C
HARACTERISTICS
,
V
DD
= 3.3V±5%, T
A
= -40°C
TO
85°C
Symbol
V
OD
Parameter
Differential Output Voltage
OD
Test Conditions
Minimum
275
1.15
Typical
Maximum
425
50
1.45
50
Units
mV
mV
V
mV
Δ
V
V
OS
V
OD
Magnitude Change
Offset Voltage
V
OS
Magnitude Change
Δ
V
OS
NOTE: Please refer to Parameter Measurement Information for output information.
T
ABLE
3E. LVDS DC C
HARACTERISTICS
,
V
DD
= 2.5V±5%, T
A
= -40°C
TO
85°C
Symbol
V
OD
Parameter
Differential Output Voltage
OD
Test Conditions
Minimum
215
1.05
Typical
Maximum
430
50
1.45
50
Units
mV
mV
V
mV
Δ
V
V
OS
V
OD
Magnitude Change
Offset Voltage
V
OS
Magnitude Change
Δ
V
OS
NOTE: Please refer to Parameter Measurement Information for output information.
T
ABLE
4. C
RYSTAL
C
HARACTERISTICS
Parameter
Mode of Oscillation
Frequency
Equivalent Series Resistance (ESR)
Shunt Capacitance
NOTE: It is not recommended to overdrive the crystal input with an external clock.
24.5
Test Conditions
Minimum
Typical
Fundamental
34
50
7
MHz
Ω
pF
Maximum
Units
T
ABLE
5. AC C
HARACTERISTICS
,
V
DD
= 3.3V±5%
OR
2.5V±5%, T
A
= -40°C
TO
85°C
Symbol
f
OUT
tjit(Ø)
t
R
/ t
F
odc
Parameter
Output Frequency
RMS Phase Jitter ( Random);
NOTE 1
Output Rise/Fall Time
Output Duty Cycle
125MHz @ Integration Range:
1.875MHz - 20MHz
20% to 80%
200
48
Test Conditions
Minimum
122.5
0.32
400
52
Typical
Maximum
170
Units
MHz
ps
ps
%
NOTE 1: Please refer to the Phase Noise Plots following this section.
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
CLOCK GENERATOR
4
REVISION A 10/27/15
844021I-01 DATA SHEET
T
YPICAL
P
HASE
N
OISE AT
125MH
Z
@ 3.3V
125MHz
RMS Phase Jitter (Random)
1.875MHz to 20MHz = 0.32ps (typical)
Ethernet Filter
N
OISE
P
OWER
dBc
Hz
Raw Phase Noise Data
Phase Noise Result by adding
Ethernet Filter to raw data
O
FFSET
F
REQUENCY
(H
Z
)
T
YPICAL
P
HASE
N
OISE AT
125MH
Z
@ 2.5V
125MHz
RMS Phase Jitter (Random)
1.875MHz to 20MHz = 0.32ps (typical)
Ethernet Filter
N
OISE
P
OWER
dBc
Hz
Raw Phase Noise Data
Phase Noise Result by adding
Ethernet Filter to raw data
O
FFSET
F
REQUENCY
(H
Z
)
REVISION A 10/27/15
5
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
CLOCK GENERATOR
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