FemtoClock
®
Crystal-to- 3.3V LVPECL
Frequency Synthesizer
Datasheet
843252
General Description
The 843252 is a 2 differential output LVPECL Synthesizer designed
to generate Ethernet reference clock frequencies. Using a 25MHz,
18pF parallel resonant crystal, the following frequencies can be
generated based on the settings of 4 frequency select pins
(SELA[1:0], SELB[1:0]): 625MHz, 312.5MHz, 156.25MHz, and
125MHz.
The two banks have their own dedicated frequency select pins and
can be independently set for the frequencies mentioned above. The
843252 IDT’s 3
rd
generation low phase noise VCO technology and
can achieve 1ps or lower typical rms phase jitter, easily meeting
Ethernet jitter requirements. The 843252 is packaged in a small
16-pin TSSOP package.
Features
•
•
•
•
•
•
•
•
•
Two differential LVPECL output pairs
Using a 25MHz crystal, the two output banks can be
independently set for 625MHz, 312.5MHz, 156.25MHz or 125MHz
Crystal oscillator interface
VCO frequency: 490MHz – 680MHz
RMS Phase Jitter @ 156.25MHz, (1.875MHz – 20MHz) using a
25MHz crystal: 0.47ps (typical)
Full 3.3V supply mode
0°C to 70°C ambient operating temperature
Industrial temperature available upon request
Available in lead-free (RoHS 6) package
Block Diagram
SELA[0:1]
Pullup
2
00
01
10
11
00
01
10
11
÷1
÷2
÷3
÷4
(default)
÷2
÷4
÷5
÷8
(default)
QA
nQA
Pin Assignment
nQB
QB
V
CCO_B
SELB1
SELB0
V
CCO_A
QA
nQA
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
XTAL_IN
XTAL_OUT
V
EE
SELA1
SELA0
V
CC
V
CCA
FB_SEL
XTAL_IN
OSC
XTAL_OUT
Phase
Detector
VCO
490MHz - 680MHz
QB
nQB
Feedback Divider
0 = ÷25
(default)
1 = ÷32
FB_SEL
Pulldown
SELB[0:1]
Pullup
2
843252
16-Lead TSSOP
4.4mm x 5.0mm x 0.925mm package body
G Package
©2016 Integrated Device Technology, Inc.
1
Revision B, January 20, 2016
843252 Datasheet
Pin Description and Pin Characteristics
Table 1. Pin Descriptions
Number
1, 2
3
4,
5
6
7, 8
9
10
11
12,
13
14
15,
16
Name
nQB, QB
V
CCO_B
SELB1,
SELB0
V
CCO_A
QA, nQA
FB_SEL
V
CCA
V
CC
SELA0,
SELA1
V
EE
XTAL_OUT
XTAL_IN
Output
Power
Input
Power
Output
Input
Power
Power
Input
Power
Input
Pullup
Pulldown
Pullup
Type
Description
Bank B differential output pair. LVPECL interface levels.
Output supply pin for QB, nQB outputs.
Division select pins for Bank B. LVCMOS/LVTTL interface levels.
Output supply pin for QA, nQA outputs.
Bank A differential output pair. LVPECL interface levels.
Feedback divide select. When LOW, the feedback divider is set for ÷25. When HIGH,
the feedback divider is set for ÷32. LVCMOS/LVTTL interface levels.
Analog supply pin.
Core supply pin.
Division select pins for Bank A. LVCMOS/LVTTL interface levels.
Negative supply pin.
Crystal oscillator interface XTAL_IN is the input, XTAL_OUT is the output.
NOTE:
Pullup and Pulldown
refer to internal input resistors. See Table 2,
Pin Characteristics,
for typical values.
Table 2. Pin Characteristics
Symbol
C
IN
R
PULLUP
Parameter
Input Capacitance
Input Pullup Resistor
Test Conditions
Minimum
Typical
4
51
51
Maximum
Units
pF
k
k
R
PULLDOWN
Input Pulldown Resistor
©2016 Integrated Device Technology, Inc.
2
Revision B, January 20, 2016
843252 Datasheet
Function Tables
Table 3A. Bank A Frequency Table
Inputs
Crystal Frequency
(MHz)
25
25
20
22.5
25
24
20
19.44
19.44
15.625
18.75
19.44
18.75
15.625
Feedback
Divider
25
25
25
25
25
25
25
32
32
32
32
32
32
32
Bank A
Output
Divider
1
2
2
3
4
4
4
1
2
2
3
4
4
4
M/N
Multiplication
Factor
25
12.5
12.5
8.333
6.25
6.25
6.25
32
16
16
10.667
8
8
8
QA, nQA
Output
Frequency
(MHz)
625
312.5
250
187.5
156.25
150
125
622.08
311.04
250
200
155.52
150
125
FB_SEL
0
0
0
0
0
0
0
1
1
1
1
1
1
1
SELA1
0
0
0
1
1
1
1
0
0
0
1
1
1
1
SELA0
0
1
1
0
1
1
1
0
1
1
0
1
1
1
©2016 Integrated Device Technology, Inc.
3
Revision B, January 20, 2016
843252 Datasheet
Table 3B. Bank B Frequency Table
Inputs
Crystal Frequency
(MHz)
25
20
25
24
20
25
25
24
20
19.44
15.625
19.44
18.75
15.625
15.625
19.44
18.75
15.625
Feedback
Divider
25
25
25
25
25
25
25
25
25
32
32
32
32
32
32
32
32
32
Bank B
Output
Divider
2
2
4
4
4
5
8
8
8
2
2
4
4
4
5
8
8
8
M/N
Multiplicatio
n Factor
12.5
12.5
6.25
6.25
6.25
5
3.125
3.125
3.125
16
16
8
8
8
6.4
4
4
4
QB, nQB
Output
Frequency
(MHz)
312.5
250
156.25
150
125
125
78.125
75
62.5
311.04
250
155.52
150
125
100
77.76
75
62.5
FB_SEL
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
SELB1
0
0
0
0
0
1
1
1
1
0
0
0
0
0
1
1
1
1
SELB0
0
0
1
1
1
0
1
1
1
0
0
1
1
1
0
1
1
1
Table 3C. Output Bank A Configuration Select
Function Table
Inputs
SELA1
0
0
1
1
SELA0
0
1
0
1
Outputs
QA, nQA
÷1
÷2
÷3
÷4 (default)
Table 3D. Output Bank B Configuration Select
Function Table
Inputs
SELB1
0
0
1
1
SELB0
0
1
0
1
Outputs
QB, nQB
÷2
÷4
÷5
÷8 (default)
Table 3E. Feedback Divider Configuration
Select Function Table
Input
FB_SEL
0
1
Feedback Divide
÷25 (default)
÷32
©2016 Integrated Device Technology, Inc.
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Revision B, January 20, 2016
843252 Datasheet
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
CC
Inputs, V
I
Outputs, I
O
Continuos Current
Surge Current
Package Thermal Impedance,
JA
Storage Temperature, T
STG
Rating
4.6V
-0.5V to V
CC
+ 0.5V
50mA
100mA
92.4C/W (0 mps)
-65C to 150C
DC Electrical Characteristics
Table 4A. Power Supply DC Characteristics, V
CC
= V
CCO_A
= V
CCO_B
= 3.3V ± 5%, V
EE
= 0V, T
A
= 0°C to 70°C
Symbol
V
CC
V
CCA
V
CCO_A,
V
CCO_B
I
CCA
I
EE
Parameter
Core Supply Voltage
Analog Supply Voltage
Power Supply Voltage
Analog Supply Current
Power Supply Current
Test Conditions
Minimum
3.135
V
CC
– 0.10
3.135
Typical
3.3
3.3
3.3
Maximum
3.465
V
CC
3.465
10
145
Units
V
V
V
mA
mA
Table 4B. LVCMOS/LVTTL DC Characteristics,V
CC
= V
CCO_A
= V
CCO_B
= 3.3V ± 5%, V
EE
= 0V, T
A
= 0°C to 70°C
Symbol
V
IH
V
IL
I
IH
Parameter
Input High Voltage
Input Low Voltage
FB_SEL
Input High Current
SELA[1:0],
SELB[1:0]
FB_SEL
I
IL
Input Low Current
SELA[1:0],
SELB[1:0]
V
CC
= V
IN
= 3.465V
V
CC
= V
IN
= 3.465V
V
CC
= 3.465V, V
IN
= 0V
V
CC
= 3.465V, V
IN
= 0V
-5
-150
Test Conditions
Minimum
2
-0.3
Typical
Maximum
V
CC
+ 0.3
0.8
150
5
Units
V
V
µA
µA
µA
µA
©2016 Integrated Device Technology, Inc.
5
Revision B, January 20, 2016
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