FemtoClocks Crystal-TO-LVDS
Frequency Synthesizer
844002I-01
DATA SHEET
General Description
The 844002I-01 is a 2 output LVDS Synthesizer optimized to
generate Ethernet reference clock frequencies. Using a 25MHz,
18pF parallel resonant crystal, the following frequencies can be
generated based on the 2 frequency
select pins (F_SEL[1:0]): 156.25MHz, 125MHz and 62.5MHz. The
844002I-01 uses IDT’s 3
rd
generation low phase noise VCO
technology and can achieve <1ps typical rms phase jitter, easily
meeting Ethernet jitter requirements. The 844002I-01 is packaged
in a small 20-pin TSSOP package.
Features
•
•
•
•
•
•
•
•
Two differential LVDS outputs
Selectable crystal oscillator interface or
single-ended LVCMOS/LVTTL input
Supports the following output frequencies: 156.25MHz,
125MHz, 62.5MHz
VCO range: 560MHz – 680MHz
RMS phase jitter @ 156.25MHz, using a 25MHz crystal
(1.875MHz – 20MHz): 0.41ps (typical)
Full 2.5V supply mode
-40°C to 85°C ambient operating temperature
Available in lead-free (RoHS 6) package
Block Diagram
Pin Assignment
F_SEL[1:0]
Pulldown
PLL_SEL
Pulldown
F_SEL[1:0]
0 0 ÷4
0 1 ÷5
1 0 ÷10
1 1 not used
2
Q0
1
Q0
nc
V
DDO
Q0
Q0
MR
PLL_SEL
nc
V
DDA
F_SEL0
V
DD
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
V
DDO
Q1
Q1
GND
nc
XTAL_SEL
REF_CLK
XTAL_IN
XTAL_OUT
F_SEL1
REF_CLK
Pulldown
25MHz
1
XTAL_IN
OSC
XTAL_OUT
XTAL_SEL
Pulldown
0
Phase
Detector
VCO
625MHz
(w/25MHz
Reference)
0
Q1
Q1
M = 25 (fixed)
MR
Pulldown
844002I-01
20-Lead TSSOP
6.5mm x 4.4mm x 0.925mm
package body
G Package
Top View
844002I-01 Rev D 6/9/15
1
©2015 Integrated Device Technology, Inc.
844002I-01 DATA SHEET
Table 1. Pin Descriptions
Number
1, 7
2, 20
3, 4
Name
nc
V
DDO
Q0, Q0
Power
Output
Type
Unused
Description
No connect.
Output supply pins.
Differential output pair. LVDS interface levels.
Active HIGH Master Reset. When logic HIGH, the internal dividers are reset
causing the true outputs Qx to go low and the inverted outputs Qx to go high.
When logic LOW, the internal dividers and the outputs are enabled.
LVCMOS/LVTTL interface levels.
Selects between the PLL and REF_CLK as input to the dividers. When LOW,
selects PLL (PLL Enable). When HIGH, deselects the reference clock (PLL
Bypass). LVCMOS/LVTTL interface levels.
Analog supply pin.
Pulldown
Frequency select pins. LVCMOS/LVTTL interface levels.
Core supply pins.
Parallel resonant crystal interface. XTAL_OUT is the output,
XTAL_IN is the input.
Pulldown
Pulldown
Non-inverting differential clock input.
Selects between crystal or REF_CLK inputs as the PLL Reference source.
Selects XTAL inputs when LOW. Selects REF_CLK when HIGH.
LVCMOS/LVTTL interface levels.
No connect.
Power supply ground.
Differential output pair. LVDS interface levels.
5
MR
Input
Pulldown
6
8
9,
11
10
12,
13
14
15
16
17
18, 19
PLL_SEL
V
DDA
FSEL0,
F_SEL1
V
DD
XTAL_OUT
,
XTAL_IN
REF_CLK
XTAL_SEL
nc
GND
Q1, Q1
Input
Power
Input
Power
Input
Input
Input
Unused
Power
Output
Pulldown
NOTE:
Pulldown
refers to internal input resistors. See Table 2,
Pin Characteristics,
for typical values.
Table 2. Pin Characteristics
Symbol
C
IN
R
PULLDOWN
Parameter
Input Capacitance
Input Pulldown Resistor
Test Conditions
Minimum
Typical
4
51
Maximum
Units
pF
k
FEMTOCLOCKS CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER
2
Rev D 6/9/15
844002I-01 DATA SHEET
Absolute Maximum Ratings
NOTE: Stresses beyond those listed under
Absolute Maximum Ratings
may cause permanent damage to the device.
These ratings are stress specifications only. Functional operation of product at these conditions or any conditions beyond
those listed in the
DC Characteristics or AC Characteristics
is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect product reliability.
Item
Supply Voltage, V
DD
Inputs, V
I
Outputs, I
O
Continuous Current
Surge Current
Package Thermal Impedance,
JA
Storage Temperature, T
STG
Rating
4.6V
-0.5V to V
DD
+ 0.5V
10mA
15mA
73.2C/W (0 lfpm)
-65C to 150C
DC Electrical Characteristics
Table 3A. Power Supply DC Characteristics,
V
DD
= V
DDA
= V
DDO
= 2.5V ± 5%, T
A
= -40°C to 85°C
Symbol
V
DD
V
DDA
V
DDO
I
DD
I
DDA
I
DDO
Parameter
Core Supply Voltage
Analog Supply Voltage
Output Supply Voltage
Power Supply Current
Analog Supply Current
Output Supply Current
Test Conditions
Minimum
2.375
2.375
2.375
Typical
2.5
2.5
2.5
Maximum
2.625
2.625
2.625
98
12
98
Units
V
V
V
mA
mA
mA
Table 3B. LVCMOS/LVTTL DC Characteristics,
V
DD
= V
DDA
= V
DDO
= 2.5V ± 5%, T
A
= -40°C to 85°C
Symbol
V
IH
V
IL
I
IH
Parameter
Input High Voltage
Input Low Voltage
Input High Current
REF_CLK, MR,
FSEL0, FSEL1,
PLL_SEL, XTAL_SEL
REF_CLK, MR,
FSEL0, FSEL1,
PLL_SEL, XTAL_SEL
Test Conditions
2.5V
2.5V
V
DD
= V
IN
= 2.625V
Minimum
1.7
-0.3
Typical
Maximum
V
DD
+ 0.3
0.7
150
Units
V
V
µA
I
IL
Input Low Current
V
DD
= 2.625V, V
IN
= 0V
-5
µA
FEMTOCLOCKS CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER
3
Rev D 6/9/15
844002I-01 DATA SHEET
Table 3C. LVDS DC Characteristics,
V
DD
= V
DDA
= V
DDO
= 2.5V ± 5%, T
A
= -40°C to 85°C
Symbol
V
OD
V
OD
V
OS
V
OS
Parameter
Differential Output Voltage
V
OD
Magnitude Change
Offset Voltage
V
OS
Magnitude Change
0.7
Test Conditions
Minimum
240
40
1.1
50
1.5
Typical
Maximum
550
Units
mV
mV
V
mV
Table 4. Crystal Characteristics
Parameter
Mode of Oscillation
Frequency
Equivalent Series Resistance (ESR)
Shunt Capacitance
Drive Level
22.4
Test Conditions
Minimum
Typical
Fundamental
25
27.2
50
7
1
MHz
Maximum
Units
pF
mW
AC Electrical Characteristics
Table 5. AC Characteristics,
V
DD
= V
DDA
= V
DDO
= 2.5V ± 5%, T
A
= -40°C to 85°C
Symbol
f
OUT
tsk(o)
tjit(Ø)
t
R
/ t
F
odc
t
L
Parameter
Output Frequency
Output Skew; NOTE 1, 2
156.25MHz, (1.875MHz – 20MHz)
RMS Phase Jitter, (Random);
NOTE 3
Output Rise/Fall Time
Output Duty Cycle
PLL Lock Time
125MHz, (1.875MHz – 20MHz)
62.5MHz, (1.875MHz – 20MHz)
20% to 80%
250
48
Test Conditions
FSEL[1:0] = 00
FSEL[1:0] = 01
FSEL[1:0] = 10
Minimum
140
112
56
5
0.41
0.44
0.47
550
52
100
Typical
Maximum
170
136
68
20
Units
MHz
MHz
MHz
ps
ps
ps
ps
ps
%
ms
NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when device is
mounted in a test socket with maintained transverse airflow greater than 500 lfpm. Device will meet specifications after thermal equilibrium has
been reached under these conditions.
NOTE 1: Defined as skew between outputs at the same supply voltages and with equal load conditions. Measured at V
DDO
/2.
NOTE 2: This parameter is defined in accordance with JEDEC Standard 65.
NOTE 3: Please refer to the Phase Noise Plot.
Rev D 6/9/15
4
FEMTOCLOCKS CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER
844002I-01 DATA SHEET
Typical Phase Noise at 156.25MHz
-10
-20
-30
-40
-50
-60
dBc
Hz
-70
-80
-90
-100
156.25MHz
RMS Phase Jitter (Random)
1.875MHz to 20MHz = 0.41ps (typical)
Noise Power
-110
-120
-130
-140
Raw Phase Noise Data
-160
-170
-180
-190
1k
10k
100k
➝
-150
Phase Noise Result by adding a
Ethernet filter to raw data
1M
10M
100M
Offset Frequency (Hz)
FEMTOCLOCKS CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER
5
➝
➝
0
Ehternet Filter
Rev D 6/9/15
单片机
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