FemtoClock
®
NG
Universal Frequency Translator
General Description
The IDT8T49N105I is a highly flexible FemtoClock® NG general
purpose, low phase noise Universal Frequency Translator /
Synthesizer with alarm and monitoring functions suitable for
networking and communications applications. It is able to generate
any output frequency in the 0.98MHz - 312.5MHz range and most
output frequencies in the 312.5MHz - 1,300MHz range (see Table 3
for details). A wide range of input reference clocks and a range of
low-cost fundamental mode crystal frequencies may be used as the
source for the output frequency.
The IDT8T49N105I has three operating modes to support a very
broad spectrum of applications:
1) Frequency Synthesizer
IDT8T49N105I
DATA SHEET
Features
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Fourth generation FemtoClock® NG technology
Universal Frequency Translator (UFT) / Frequency Synthesizer
Single output (Q, nQ), programmable as LVPECL or LVDS
Zero ppm frequency translation
Single differential input supports the following input types:
LVPECL, LVDS, LVHSTL, HCSL
Input frequency range: 8kHz - 710MHz
Crystal input frequency range: 16MHz - 40MHz
Two factory-set register configurations for power-up default state
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•
Synthesizes output frequencies from a 16MHz - 40MHz
fundamental mode crystal.
Fractional feedback division is used, so there are no
requirements for any specific crystal frequency to produce the
desired output frequency with a high degree of accuracy.
Applications: PCI Express, Computing, General Purpose
Translates any input clock in the 16MHz - 710MHz frequency
range into any supported output frequency.
This mode has a high PLL loop bandwidth in order to track input
reference changes, such as Spread-Spectrum Clock
modulation, so it will not attenuate much jitter on the input
reference.
Applications: Networking & Communications.
Translates any input clock in the 8kHz -710MHz frequency
range into any supported output frequency.
This mode supports PLL loop bandwidths in the 10Hz - 580Hz
range and makes use of an external crystal to provide
significant jitter attenuation.
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Power-up default configuration pin or register selectable
Configurations customized via One-Time Programmable ROM
Settings may be overwritten after power-up via I
2
C
I
2
C Serial interface for register programming
2) High-Bandwidth Frequency Translator
RMS phase jitter at 155.52MHz, using a 40MHz crystal LVDS
Output (12kHz - 20MHz): 439fs (typical), Low Bandwidth Mode
(FracN)
RMS phase jitter at 400MHz, using a 40MHz crystal
(12kHz - 40MHz):285fs (typical), Synthesizer Mode (Integer FB)
Output supply voltage modes:
V
CC
/V
CCA
/V
CCO
3.3V/3.3V/3.3V
3.3V/3.3V/2.5V (LVPECL only)
2.5V/2.5V/2.5V
-40°C to 85°C ambient operating temperature
Lead-free (RoHS 6) packaging
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3) Low-Bandwidth Frequency Translator
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Pin Assignment
LOCK_IND
V
CC
V
CCO
V
EE
nc
nc
S_A0
S_A1
CONFIG
SCLK
SDATA
V
CC
PLL_BYPASS
nc
19
18
17
14
13
12
8
V
EE
11
9
10
nc
nc
OE
nQ
nc
7
V
CC
nc
nc
This device provides two factory-programmed default power-up
configurations burned into One-Time Programmable (OTP) memory.
The configuration to be used is selected by the CONFIG pin. The two
configurations are specified by the customer and are programmed by
IDT during the final test phase from an on-hand stock of blank
devices. The two configurations may be completely independent of
one another.
One usage example might be to install the device on a line card with
two optional daughter cards: an OC-12 option requiring a 622.08MHz
LVDS clock translated from a 19.44MHz input and a Gigabit Ethernet
option requiring a 125MHz LVPECL clock translated from the same
19.44MHz input reference.
To implement other configurations, these power-up default settings
can be overwritten after power-up using the I
2
C interface and the
device can be completely reconfigured. However, these settings
would have to be re-written next time the device powers-up.
nc
nc
LF0
LF1
V
EE
V
CCA
HOLDOVER
CLKBAD
nc
XTALBAD
30
29 28 27 26 25 24 23 22 21
31
20
32
33
34
35
37
38
39
40
1
2
3
V
CC
4
nc
5
CLK
6
nCLK
XTAL_IN
XTAL_OUT
8T49N105
40 Lead VFQFN
6mm x 6mm x 0.925mm
16
36
E-Pad 4.65mm x 4.65mm
15
K Package
Top View
IDT8T49N105ANLGI REVISION A MAY 24, 2013
1
Q
©2013 Integrated Device Technology, Inc.
IDT8T49N105I Data Sheet
FemtoClock
®
NG Universal Frequency Translator
Complete Block Diagram
IDT8T49N105ANLGI REVISION A MAY 24, 2013
2
©2013 Integrated Device Technology, Inc.
IDT8T49N105I Data Sheet
FemtoClock
®
NG Universal Frequency Translator
Table 1. Pin Descriptions
Number
1
2
3, 7, 13, 29
4, 9, 10, 11,
19, 20, 22, 23,
24, 31, 32, 39
8, 21, 35
5
6
Name
XTAL_IN
XTAL_OUT
V
CC
nc
V
EE
CLK
nCLK
Input
Power
Unused
Power
Input
Input
Pulldown
Pullup/
Pulldown
Type
Description
Crystal Oscillator interface designed for 12pF parallel resonant crystals.
XTAL_IN (pin 1) is the input and XTAL_OUT (pin 2) is the output.
Core supply pins. All must be either 3.3V or 2.5V.
No connect. These pins are to be left unconnected.
Negative supply pins.
Non-inverting differential clock input.
Inverting differential clock input. V
CC
/2 default when left floating (set by the
internal pullup and pulldown resistors).
Bypasses the VCXO PLL. In bypass mode, outputs are clocked off the falling
edge of the input reference. LVCMOS/LVTTL interface levels.
0 = PLL Mode (default)
1 = PLL Bypassed
I
2
C Data Input/Output. Open drain.
I
2
C Clock Input. LVCMOS/LVTTL interface levels.
Configuration Pin. Selects between one of two factory programmable pre-set
power-up default configurations. The two configurations can have different
output/input frequency translation ratios, different PLL loop bandwidths, etc.
These default configurations can be overwritten after power-up via I
2
C if the
user so desires. LVCMOS/LVTTL interface levels.
0 = Configuration 0 (default)
1 = Configuration 1
I
2
C Address Bit 1. LVCMOS/LVTTL interface levels.
I
2
C Address Bit 0. LVCMOS/LVTTL interface levels.
Output supply pins for Q, nQ output. Either 2.5V or 3.3V.
Differential output pair. Output type is programmable to LVDS or LVPECL
interface levels.
Pullup
Active High Output Enable for Q, nQ. LVCMOS/LVTTL interface levels.
0 = Output pins high-impedance
1 = Output switching (default)
Lock Indicator - indicates that the PLL is in a locked condition.
LVCMOS/LVTTL interface levels.
Loop filter connection node pins. LF0 is the output. LF1 is the input.
Analog supply voltage. See Applications section for details on how to
connect this pin.
Alarm output reflecting if the device is in a holdover state. LVCMOS/LVTTL
interface levels.
0 = Device is locked to a valid input reference
1 = Device is not locked to a valid input reference
Alarm output reflecting the state of CLK. LVCMOS/LVTTL interface levels.
0 = Input Clock is switching within specifications
1 = Input Clock is out of specification
Alarm output reflecting the state of XTAL. LVCMOS/LVTTL interface levels.
0 = crystal is switching within specifications
1 = crystal is out of specification
12
PLL_BYPASS
Input
Pulldown
14
15
SDATA
SCLK
I/O
Input
Pullup
Pullup
16
CONFIG
Input
Pulldown
17
18
25
26, 27
S_A1
S_A0
V
CCO
nQ, Q
Input
Input
Power
Output
Pulldown
Pulldown
28
OE
Input
30
33, 34
36
LOCK_IND
LF0, LF1
V
CCA
Output
Analog
I/O
Power
37
HOLDOVER
Output
38
CLK_BAD
Output
40
XTAL_BAD
Output
NOTE:
Pullup and Pulldown
refer to internal input resistors. See Table 2,
Pin Characteristics,
for typical values.
IDT8T49N105ANLGI REVISION A MAY 24, 2013
3
©2013 Integrated Device Technology, Inc.
IDT8T49N105I Data Sheet
FemtoClock
®
NG Universal Frequency Translator
Table 2. Pin Characteristics
Symbol
C
IN
R
PULLUP
R
PULLDOWN
Parameter
Input Capacitance
Input Pullup Resistor
Input Pulldown Resistor
Test Conditions
Minimum
Typical
3.5
51
51
Maximum
Units
pF
k
k
IDT8T49N105ANLGI REVISION A MAY 24, 2013
4
©2013 Integrated Device Technology, Inc.
IDT8T49N105I Data Sheet
FemtoClock
®
NG Universal Frequency Translator
Functional Description
The IDT8T49N105I is designed to provide almost any desired output
frequency within its operating range (0.98 - 1300MHz) from any input
source in the operating range (8kHz - 710MHz). It is capable of
synthesizing frequencies from a crystal or crystal oscillator source.
The output frequency is generated regardless of the relationship to
the input frequency. The output frequency will be exactly the required
frequency in most cases. In most others, it will only differ from the
desired frequency by a few ppb. IDT configuration software will
indicate the frequency error, if any. The IDT8T49N105I can translate
the desired output frequency from one of two input clocks. Again, no
relationship is required between the input and output frequencies in
order to translate to the output clock rate. In this frequency translation
mode, a low-bandwidth, jitter attenuation option is available that
makes use of an external fixed-frequency crystal or crystal oscillator
to translate from a noisy input source. If the input clock is known to
be fairly clean or if some modulation on the input needs to be tracked,
then the high-bandwidth frequency translation mode can be used,
without the need for the external crystal.
The input clock references and crystal input are monitored
continuously and appropriate alarm outputs are raised both as
register bits and hard-wired pins in the event of any
out-of-specification conditions arising. Clock switching is supported
in manual, revertive & non-revertive modes.
The IDT8T49N105I has two factory-programmed configurations that
may be chosen from as the default operating state after reset. This is
intended to allow the same device to be used in two different
applications without any need for access to the I
2
C registers. These
defaults may be over-written by I
2
C register access at any time, but
those over-written settings will be lost on power-down. Please
contact IDT if a specific set of power-up default settings is desired.
ratios within the IDT8T49N105I for the two different card
configurations. Access via I
2
C would not be necessary for operation
using either of the internal configurations.
Operating Modes
The IDT8T49N105I has three operating modes which are set by the
MODE_SEL[1:0] bits. There are two frequency translator modes -
low bandwidth and high bandwidth and a frequency synthesizer
mode. The device will operate in the same mode regardless of which
configuration is active.
Please make use of IDT-provided configuration applications to
determine the best operating settings for the desired configurations
of the device.
Output Dividers & Supported Output Frequencies
In all 3 operating modes, the output stage behaves the same way, but
different operating frequencies can be specified in the two
configurations.
The internal VCO is capable of operating in a range anywhere from
1.995GHz - 2.6GHz. It is necessary to choose an integer multiplier of
the desired output frequency that results in a VCO operating
frequency within that range. The output divider stage N[10:0] is
limited to selection of integers from 2 to 2046. Please refer to Table 3
for the values of N applicable to the desired output frequency.
Table 3. Output Divider Settings & Frequency Ranges
Register
Setting
Nn[10:0]
0000000000x
00000000010
00000000011
00000000100
00000000101
0000000011x
0000000100x
0000000101x
0000000110x
0000000111x
0000001000x
0000001001x
...
1111111111x
Frequency
Divider
N
2
2
3
4
5
6
8
10
12
14
16
18
Even N
2046
Minimum
f
OUT
(MHz)
997.5
997.5
665
498.75
399
332.5
249.4
199.5
166.3
142.5
124.7
110.8
1995 / N
0.98
Maximum
f
OUT
(MHz)
1300
1300
866.7
650
520
433.3
325
260
216.7
185.7
162.5
144.4
2600 / N
1.27
Configuration Selection
The IDT8T49N105I comes with two factory-programmed default
configurations. When the device comes out of power-up reset the
selected configuration is loaded into operating registers. The
IDT8T49N105I uses the state of the CONFIG pin or CONFIG register
bit (controlled by the CFG_PIN_REG bit) to determine which
configuration is active. When the output frequency is changed either
via the CONFIG pin or via internal registers, the output behavior may
not be predictable during the register writing and output settling
periods. Devices sensitive to glitches or runt pulses may have to be
reset once reconfiguration is complete.
Once the device is out of reset, the contents of the operating registers
can be modified by write access from the I
2
C serial port. Users that
have a custom configuration programmed may not require I
2
C
access.
It is expected that the IDT8T49N105I will be used almost exclusively
in a mode where the selected configuration will be used from device
power-up without any changes during operation. For example, the
device may be designed into a communications line card that
supports different I/O modules such as a standard OC-12 module
running at 622.08MHz or a (255/237) FEC rate OC-12 module
running at 669.32MHz. The different I/O modules would result in a
different level on the CONFIG pin which would select different divider
IDT8T49N105ANLGI REVISION A MAY 24, 2013
5
©2013 Integrated Device Technology, Inc.
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