845254 Datasheet, PDF (1/20 Pages) Integrated Device Technology – FemtoClock Crystal-to-3.3V, 2.5V

FemtoClock^® Crystal-to-3.3V, 2.5V
CML Clock Generator
845254
DATA SHEET
General Description
The 845254 is a 3.3V/2.5V CML clock generator designed for
Ethernet applications. The device synthesizes either a 50MHz,
62.5MHz, 100MHz, 125MHz, 156.25MHz, 250MHz or 312.5MHz
clock signal with excellent phase jitter performance. The clock signal
is distributed to four low-skew differential CML outputs. The device is
suitable for driving the reference clocks of Ethernet PHYs. The
device supports 3.3V and 2.5V voltage supply and is packaged in a
small, lead-free (RoHS 6) 32-lead VFQFN package. The extended
temperature range supports telecommunication, wireless
infrastructure and networking end equipment requirements.
Features
• Clock generation of: 50MHz, 62.5MHz, 100MHz, 125MHz,
156.25MHz, 250MHz and 312.5MHz
• Four differential CML clock output pairs
• 25MHz reference clock (selectable internal crystal oscillator and
external LVCMOS clock)
• RMS phase jitter @ 125MHz, using a 25MHz crystal
(1.875MHz – 20MHz): 0.405ps (typical)
Offset
Noise Power
100Hz.................... -104.6 dBc/Hz
1kHz.................... -118.4 dBc/Hz
10kHz................... -124.1 dBc/Hz
100kHz................... -125.3 dBc/Hz
• LVCMOS interface levels for the control inputs
• Full 3.3V and 2.5V supply voltage
• Available in lead-free (RoHS 6) 32 VFQFN package
• -40°C to 85°C ambient operating temperature
• Replacement part: 843002AYLF
Block Diagram
XTAL_IN
OSC
XTAL_OUT
REF_CLK ^Pulldown
REF_SEL ^Pulldown
FBSEL ^Pulldown
nBYPASS ^Pullup
FSEL[1:0] ^Pulldown
nOE ^Pulldown
0
Phase
f_{REF Detector}
1
VCO
490-680
MHz
÷20,
÷25 (default)
0 ^{÷2 (default),}
÷4,
÷5,
1 _÷10
2
Pin Assignment
Q0
nQ0
Q1
nQ1
Q2
nQ2
Q3
nQ3
32 31 30 29 28 27 26 25
nQ0 1
24 nQ3
Q0 2
23 Q3
VDD 3
22 REF_SEL
nOE 4
21 FSEL1
nc 5
20 FSEL0
nc 6
nc 7
19 ^nc
18 VDD
nc 8
17 nc
9 10 11 12 13 14 15 16
845254
32 lead VFQFN
5.0mm x 5.0mm x 0.925mm package body
K Package
Top View
845254 REVISION B 08/25/15
1
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