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Renesas Electronics Components Datasheet

845264 Datasheet

Crystal-to-CML Clock Generator

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FemtoClock®Crystal-to-CML Clock Generator
845264
DATA SHEET
General Description
The 845264 is a 3.3V, 2.5V CML clock generator designed for
Ethernet applications. The device synthesizes four clock frequencies
on two separately selectable output banks. Each bank has either a
62.5MHz, 125MHz, 156.25MHz or 312.5MHz clock signal with
excellent phase jitter performance. Each clock frequency is
distributed to two low-skew differential CML output banks with a total
of four 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: 62.5MHz, 125MHz, 156.25MHz and
312.5MHz
Two banks of two differential CML clock outputs
Crystal interface designed for 25MHz, 12pF parallel resonant
crystal
RMS phase jitter @ 125MHz, using a 25MHz crystal
(1.875MHz – 20MHz): 0.486ps (typical)
Offset
Single-side Band Phase Noise
100Hz ............................-97 dBc/Hz
1kHz...............................-118 dBc/Hz
10kHz.............................-125 dBc/Hz
100kHz...........................-123 dBc/Hz
LVCMOS interface levels for the control inputs
Full 3.3V and 2.5V supply voltage
Lead-free (RoHS 6) 32 VFQFN packaging
-40°C to 85°C ambient operating temperature
Block Diagram
nOEA
FSELA[1:0]
Pulldown
Pulldown
XTAL_IN
XTAL_OUT
REF_CLK
REF_SEL
nBYPASS
FSELB[1:0]
nOEB
OSC
Pulldown
Pulldown
Pullup
Pulldown
Pulldown
0
Phase
fREF Detector
VCO
1
÷25
0
÷2, ÷4,
÷5, ÷10
1
÷2, ÷4,
÷5, ÷10
Pin Assignment
QA0
nQA0
QA1
nQA1
QB0
nQB0
QB1
nQB1
32 31 30 29 28 27 26 25
nQA0 1
24 nQB0
QA0 2
23 QB0
VDD 3
nOEA 4
845264
22 REF_SEL
21 FSELA1
nc 5
20 FSELA0
nc 6
19 FSELB1
nc 7
18 FSELB0
nc 8
17 VDD
9 10 11 12 13 14 15 16
32 lead, 5mm x 5mm VFQFN
845264 REVISION B 07/20/15
1 ©2015 Integrated Device Technology, Inc.
\


Renesas Electronics Components Datasheet

845264 Datasheet

Crystal-to-CML Clock Generator

No Preview Available !

845264 DATA SHEET
Pin Descriptions and Characteristics
Table 1. Pin Descriptions
Number
Name
Type
Description
1, 2
nQA0, QA0
Output
Bank A differential clock output pair. CML interface levels.
3, 17
VDD Power
Core supply pins.
4
nOEA
Input
Pulldown Output enable pin for Bank A outputs. See Table 3E for function.
LVCMOS/LVTTL interface levels.
5, 6, 7, 8, 9,
16, 25, 32
nc
Unused
Do not connect.
10
VDDA
Power
Analog supply pin.
11
nBYPASS
Input
Pullup PLL bypass pin. See Table 3D for function. LVCMOS/LVTTL interface levels.
12
REF_CLK
Input
Pulldown Single-ended reference clock input. LVCMOS/LVTTL interface levels.
13, 29
GND
Power
Power supply ground.
14,
15
XTAL_OUT,
XTAL_IN
Input
Crystal oscillator interface. XTAL_IN is the input, XTAL_OUT is the output.
18,
19
FSELB0,
FSELB1
Input
Pulldown Output frequency divider select enable pins for Bank B outputs.
See Table 3C for function. LVCMOS/LVTTL interface levels.
20,
21
FSELA0,
FSELA1
Input
Pulldown Output frequency divider select enable pins for Bank A outputs.
See Table 3B for function. LVCMOS/LVTTL interface levels.
22
23, 24
REF_SEL
QB0, nQB0
Input
Output
Pulldown
PLL reference clock select pin. See Table 3A for function.
LVCMOS/LVTTL interface levels.
Bank B differential clock output pair. CML interface levels.
26
27, 28
30, 31
nOEB
nQB1, QB1
nQA1, QA1
Input
Output
Output
Pulldown
Output enable pin for Bank B outputs. See Table 3F for function.
LVCMOS/LVTTL interface levels.
Bank B differential clock output pair. CML interface levels.
Bank A differential clock output pair. CML interface levels.
NOTE: Pulldown and Pullup refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
Table 2. Pin Characteristics
Symbol
Parameter
nBYPASS,
CIN
Input
Capacitance
REF_SEL,
nOEA, nOEB,
FSELB0, FSELB1,
FSELA0, FSELA1
RPULLDOWN
RPULLUP
Input Pulldown Resistor
Input Pullup Resistor
Test Conditions
Minimum Typical Maximum Units
4 pF
51 k
51 k
REVISION B 07/20/15
2 FEMTOCLOCK®CRYSTAL-TO-CML CLOCK GENERATOR


Part Number 845264
Description Crystal-to-CML Clock Generator
Maker Renesas
Total Page 24 Pages
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