Programmable FemtoClock® NG LVPECL/LVDS
Clock Generator with 4-Outputs
IDT8T49N004I
DATASHEET
General Description
Features
The IDT8T49N004I is a four output Clock Generator with selectable
LVDS or LVPECL outputs. The IDT8T49N004I can generate any one
of four frequencies from a single crystal or reference clock. The four
frequencies are selected from the Frequency Selection Table (Table
3A) and are programmed via I2C interface. The four predefined
frequencies are selected in the user application by two frequency
selection pins. Note the desired programmed frequencies must be
used with the corresponding crystal or clock frequency as indicated
in Table 3A.
•
•
•
Fourth Generation FemtoClock NG PLL technology
•
•
FemtoClock NG VCO Range: 1.91GHz - 2.5GHz
•
•
•
•
RMS phase jitter at 156.25MHz (10kHz - 1MHz): 175fs (typical)
•
•
-40°C to 85°C ambient operating temperature
Excellent phase noise performance is maintained with IDT’s Fourth
Generation FemtoClock® NG PLL technology, which delivers
sub-400fs RMS phase jitter.
Four selectable LVPECL or LVDS outputs via I2C
CLK, nCLK input pair can accept the following differential input
levels: LVPECL, LVDS, HCSL
RMS phase jitter at 156.25MHz (12kHz - 20MHz):
228fs (typical)
Full 2.5V or 3.3V power supply
I2C programming interface
PCI Express (2.5Gb/s), Gen 2 (5Gb/s), and Gen 3 (8Gb/s)
jitter compliant
Lead-free (RoHS 6) packaging
FSEL1
VEE
nQ3
Q3
VCCO
nQ2
Q2
VEE
Pin Assignment
SCLK
25
24 23 22 21 20 19 18 17
16
VCC
SDATA
26
15
VEE
12
CLK
30
11
VEE
VCC
31
10
XTAL_OUT
CLK_SEL
32
9
VEE
1
2
3
4
5
6
7
8
nc
29
VEE
VEE
LOCK
nQ1
nCLK
Q1
FSEL0
13
VCCO
14
28
Q0
27
nQ0
VEE
VCCA
XTAL_IN
IDT8T49N004I
32-Lead VFQFN
5mm x 5mm x 0.925mm package body
3.15mm x 3.15mm E-Pad
NL Package
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
1
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Block Diagram
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
2
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 1. Pin Descriptions
Number
Name
1, 7, 11, 15,
18, 24, 27, 30
VEE
Power
Negative supply pins.
2, 3
Q0, nQ0
Output
Differential output pair. LVPECL or LVDS interface levels.
4, 21
VCCO
Power
Output supply pins.
5, 6
Q1, nQ1
Output
Differential output pair. LVPECL or LVDS interface levels.
8
nc
Unused
No connect.
9,
10
XTAL_IN
XTAL_OUT
Input
12
CLK
Input
Pulldown
Non-inverting differential clock input.
Input
Pullup/
Pulldown
Inverting differential clock input. Internal resistor bias to VCC/2.
Pulldown
Frequency and configuration. Selects between one of four factory
programmable power-up default configurations. The four configurations can
have different PLL states, output frequencies, output styles and output
states. These default configurations can be overwritten after power-up via
I2C. LVCMOS/LVTTL interface levels.
00 = Configuration 0 (default)
01 = Configuration 1
10 = Configuration 2
11 = Configuration 3
13
nCLK
Type
Description
Crystal oscillator interface. XTAL_IN is the input, XTAL_OUT is the output.
Crystal frequency is selected from Table 3A.
14, 17
FSEL0,
FSEL1
16, 31
VCC
Power
Core supply pins.
19, 20
nQ3, Q3
Output
Differential output pair. LVPECL or LVDS interface levels.
22, 23
nQ2, Q2
Output
Differential output pair. LVPECL or LVDS interface levels.
25
SCLK
Input
Pullup
I2C Clock Input. LVCMOS/LVTTL interface levels.
26
SDATA
I/O
Pullup
I2C Data Input. Input: LVCMOS/LVTTL interface levels.
Output: Open Drain.
28
VCCA
Power
Analog supply pin.
29
LOCK
Output
PLL Lock Indicator. LVCMOS/LVTTL interface levels.
32
CLK_SEL
Input
Input
Pulldown
Input source control pin. LVCMOS/LVTTL interface levels.
0 = XTAL (default)
1 = CLK, nCLK
NOTE: Pullup and Pulldown refer to internal input resistors. See Table 2, Pin Characteristics, for typical values.
Table 2. Pin Characteristics
Symbol
Parameter
CIN
Input Capacitance
3.5
pF
RPULLDOWN
Input Pulldown Resistor
51
k
RPULLUP
Input Pullup Resistor
51
k
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
Test Conditions
3
Minimum
Typical
Maximum
Units
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Frequency Configuration
Table 3A. Frequency Configuration Examples
Output Frequencies
(MHz)
Input Frequency or
Crystal Frequency
(MHz)
Input Clock
Divider
P
Input Clock
Prescaler
PS
Feedback
Divider
M
Output Divider
N
VCO
Frequency
(MHz)
30.72
30.72
1
x2
32
64
1966.08
61.44
30.72
1
x2
32
32
1966.08
62.5
25
1
x2
40
32
2000
76.8
30.72
1
x2
40
32
2457.6
78.125
25
1
x2
50
32
2500
100
25
1
x2
40
20
2000
106.25
26.5625
1
x2
40
20
2125
122.8
30.72
1
x2
32
16
1966.08
125
25
1
x2
40
16
2000
133.33
25
1
x2
48
18
2400
148.5
27
1
x2
44
16
2376
150
25
1
x2
42
14
2100
153.6
30.72
1
x2
40
16
2457.6
155.52
19.44
1
x2
64
16
2488.32
25
1
x2
50
16
2500
100
2
x1
50
16
2500
125
5
x2
50
16
2500
159.375
26.5625
1
x2
36
12
1912.5
160
20
1
x2
48
12
1920
166.66
25
1
x2
40
12
2000
30.72
1
x2
36
12
2211.84
61.44
1
x1
36
12
2211.84
187.5
25
1
x1
90
12
2250
200
25
1
x2
40
10
2000
212.5
26.5625
1
x2
40
10
2125
250
25
1
x2
40
8
2000
300
25
1
x2
48
8
2400
19.44
1
x2
64
8
2488.32
77.76
1
x1
32
8
2488.32
155.52
2
x1
32
8
2488.32
25
1
x2
50
8
2500
125
2
x1
40
8
2500
156.25
5
x2
40
8
2500
26.5625
1
x2
36
6
1912.5
156.25
184.32
311.04
312.5
318.75
Continued on next page.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Output Frequencies
(MHz)
Input Frequency or
Crystal Frequency
(MHz)
Input Clock
Divider
P
Input Clock
Prescaler
PS
Feedback
Divider
M
Output Divider
N
VCO
Frequency
(MHz)
322.265625
25.78125
2
x1
150
6
1933.59375
375
25
1
x1
90
6
2250
400
25
1
x2
40
5
2000
425
26.5625
1
x2
40
5
2125
491.52
30.72
1
x2
32
4
1966.08
30.72
1
x2
40
4
2457.6
122.88
2
x1
40
4
2457.6
153.6
5
x2
40
4
2457.6
622.08
19.44
1
x2
64
4
2488.32
625
25
1
x2
50
4
2500
1228.88
30.72
1
x2
40
2
2457.6
614.4
NOTE: Each device supports 4 output frequencies (with related input or crystal value) as selected from this table Register Settings.
NOTE: XTAL operation: fOUT = fREF * PS * M / N; CLK, nCLK input operation: fOUT = (fREF / P) * PS * M / N.
Table 3B. I2C Register Map
Register Bit
Register
Binary
Register
Address
D7
D6
D5
D4
D3
D2
D1
D0
0
00000
M0[8]
M0[7]
M0[6]
M0[5]
M0[4]
M0[3]
M0[2]
M0[1]
1
00001
M1[8]
M1[7]
M1[6]
M1[5]
M1[4]
M1[3]
M1[2]
M1[1]
2
00010
M2[8]
M2[7]
M2[6]
M2[5]
M2[4]
M2[3]
M2[2]
M2[1]
3
00011
M3[8]
M3[7]
M3[6]
M3[5]
M3[4]
M3[3]
M3[2]
M3[1]
4
00100
unused
N0[6]
N0[5]
N0[4]
N0[3]
N0[2]
N0[1]
N0[0]
5
00101
unused
N1[6]
N1[5]
N1[4]
N1[3]
N1[2]
N1[1]
N1[0]
6
00110
unused
N2[6]
N2[5]
N2[4]
N2[3]
N2[2]
N2[1]
N2[0]
7
00111
unused
N3[6]
N3[5]
N3[4]
N3[3]
N3[2]
N3[1]
N3[0]
8
01000
unused
BYPASS0
PS0[1]
PS0[0]
P0[1]
P0[0]
CP0[1]
CP0[0]
9
01001
unused
BYPASS1
PS1[1]
PS1[0]
P1[1]
P1[0]
CP1[1]
CP1[0]
10
01010
unused
BYPASS2
PS2[1]
PS2[0]
P2[1]
P2[0]
CP2[1]
CP2[0]
11
01011
unused
BYPASS3
PS3[1]
PS3[0]
P3[1]
P3[0]
CP3[1]
CP3[0]
12
01100
reserved
LVDS_SEL0[Q3]
LVDS_SEL0[Q2]
reserved
reserved
LVDS_SEL0[Q1]
LVDS_SEL0[Q0]
reserved
13
01101
reserved
LVDS_SEL1[Q3]
LVDS_SEL1[Q2]
reserved
reserved
LVDS_SEL1[Q1]
LVDS_SEL1[Q0]
reserved
14
01110
reserved
LVDS_SEL2[Q3]
LVDS_SEL2[Q2]
reserved
reserved
LVDS_SEL2[Q1]
LVDS_SEL2[Q0]
reserved
15
01111
reserved
LVDS_SEL3[Q3]
LVDS_SEL3[Q2]
reserved
reserved
LVDS_SEL3[Q1]
LVDS_SEL3[Q0]
reserved
16
10000
reserved
OE0[Q3]
OE0[Q2]
reserved
reserved
OE0[Q1]
OE0[Q0]
reserved
17
10001
reserved
OE1[Q3]
OE1[Q2]
reserved
reserved
OE1[Q1]
OE1[Q0]
reserved
18
10010
reserved
OE2[Q3]
OE2[Q2]
reserved
reserved
OE2[Q1]
OE2[Q0]
reserved
19
10011
reserved
OE3[Q3]
OE3[Q2]
reserved
reserved
OE3[Q1]
OE3[Q0]
reserved
20
10100
reserved
reserved
reserved
reserved
reserved
reserved
unused
unused
21
10101
unused
unused
unused
unused
unused
unused
unused
unused
22
10110
unused
unused
unused
unused
unused
unused
unused
unused
23
10111
unused
unused
unused
unused
unused
unused
unused
unused
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 3C. I2C Function Descriptions
Bits
Name
Pn[1:0]
Input Clock Divider Register n
(n = 0...3)
Sets the PLL input clock divider. The divider value has the range of 1, 2, 4
and 5. See Table 3F. Pn[1:0] bits are programmed with values to support
default configuration settings for FSEL[1:0].
PSn(1:0)
Input Prescaler Register n
(n = 0...3)
Sets the PLL input clock prescaler value. Valid prescaler values are x0.5, x1
or x2. See Table 3F. Set prescaler to x2 for optimum phase noise
performance. PSn[1:0] bits are programmed with values to support default
configuration settings for FSEL[1:0].
Mn[8:1]
Integer Feedback Divider Register
n
(n = 0...3)
Sets the integer feedback divider value. Based on the FemtoClock NG VCO
range, the applicable feedback dividers settings are 16 thru 250. Please note
the register value presents bits [8:1] of Mn, the LSB of Mn is not in the
register. Mn[8:1] bits are programmed with values to support default
configuration settings for FSEL[1:0].
Nn[6:0]
Output Divider Register n
(n = 0...3)
Sets the output divider. The output divider value can range from 2, 3, 4, 5, 6
and 8, 10, 12 to 126 (step: 2). See Table 3G for the output divider coding.
Nn[6:0] bits are programmed with values to support default configuration
settings for FSEL[1:0].
CPn[1:0]
PLL Bandwidth Register n
(n = 0...3)
Sets the FemtoClock NG PLL bandwidth by controlling the charge pump
current. See Table 3H. CPn[1:0] bits are programmed with values to support
default configuration settings for FSEL[1:0].
PLL Bypass Register n
(n = 0...3)
Bypasses PLL. Output of the prescaler is routed through the output divider
N to the output fanout buffer. Programming a 1 to this bit bypasses the PLL.
Programming a 0 to this bit routes the output of the prescaler through the
PLL. BYPASSn bits are programmed with values to support default
configuration settings for FSEL[1:0].
Output Enable Register n
(n = 0...3)
Sets the outputs to Active or High Impedance. Programming a 0 to this bit
sets the outputs to High Impedance. Programming a 1, sets the outputs to
active status. OEn[Q0], OEn[Q1], OEn[Q2], and OEn[Q3] bits are
programmed with values to support default configuration settings for
FSEL[1:0].
Output Style Register n
(n = 0...3)
Sets the differential output style to either LVDS or LVPECL interface levels.
Programming a 1 to this bit sets the output styles to LVDS levels.
Programming a 0 to this bit sets the output styles to LVPECL levels.
LVDS_SELn[Q0], LVDS_SELn[Q1], LVDS_SELn[Q2], and LVDS_SELn[Q3]
bits are programmed with values to support default configuration settings for
FSEL[1:0].
BYPASSn
OEn[Q0]
OEn[Q1]
OEn[Q2]
OEn[Q3]
LVDS_SELn[Q0]
LVDS_SELn[Q1]
LVDS_SELn[Q2]
LVDS_SELn[Q3]
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
Function
6
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 3D. Feedback Divider Mn Coding
Register Bit
Mn[8:1]
Feedback Divider Mn
Do Not Use
1 thru 15
00001000
16
00001001
18
00001010
20
00001011
22
00001100 thru 00011111
24 thru 62
00100000
64
00100001
66
00100010
68
00100011
70
00100100
72
...
Mn
00110010
100
00110011
102
00110100
104
00110101
106
...
Mn
01111010
244
01111011
246
01111100
248
01111101
250
Note: Mn is always an even value. The Mn[0] bits are not implemented.
Table 3E. Input Clock Divider Pn and Prescaler PSn Coding
CLK_SEL
0
Input
XTAL
P[1:0]
xx
00
01
1
PS[1:0]
Input Clock
Divider
P
Input Clock
Prescaler
PS
Input Frequency (MHz)
Minimum
Maximum
00
1
x1
10
40
01
1
x0.5
20
40
1x
1
x2
5
40
00
1
x1
10
120
01
1
x0.5
20
240
1x
1
x2
5
60
00
2
x1
20
240
01
2
x0.5
40
480
1x
2
x2
10
120
00
4
x1
40
480
01
4
x0.5
80
800
1x
4
x2
20
240
00
5
x1
50
600
01
5
x0.5
100
800
1x
5
x2
25
300
CLK
10
11
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 3F. Output Divider Nn Coding
Register Bit
Output Frequency Range
Nn[6:0]
Output Divider
N
000000X
2
0000010
2
955
1250
0000011
3
636.67
833.33
0000100
4
477.5
625
0000101
5
382
500
000011X
6
318.33
416.67
000100X
8
238.75
312.5
000101X
10
191
250
000110X
12
159.1667
208.33
000111X
14
136.4286
178.57
001000X
16
119.375
156.25
...
N (even integer)
(1910 ÷ N)
(2500 ÷ N)
111101X
124
15.40
20.16
111111X
126
15.16
19.84
fOUT_MIN (MHz)
fOUT_MAX (MHz)
Do Not Use
NOTE: X denotes “don’t care”.
Table 3G. Charge Pump CP Settings
Register Bit
Feedback Divider (M) Value Range
CPn1
CPn0
Minimum
Maximum
0
0
16
48
0
1
48
100
1
0
100
250
1
1
192
250
NOTE: FemtoClock NG PLL stability is only guaranteed over the feedback divider ranges listed is Table 3G.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Power-up Default Configuration Description
outputs that are enabled after power-up, specified over the industrial
temperature range and housed in a lead-free (6/6 RoHS) VFQFN
package.
The IDT8T49N004I supports a variety of options such as different
output styles, number of programmed default frequencies, output enable and operating temperature range. The device options and default frequencies must be specified at the time of order and are
programmed by IDT prior to shipment. The document, Programmable FemtoClock® NG Product Ordering Guide specifies the available
order codes, including the device options and default frequency configurations. Example part number: 8T49N004A-007NLGI, specifies a
quad frequency clock generator with default frequencies of
106.25MHz, 133.333MHz, 156.25MHz and 156.25MHz, with 4 LVDS
Other order codes with respective programmed frequencies are
available from IDT upon request. After power-up changes to the output frequencies are controlled by FSEL[1:0] or the I2C interface.
Changes to the style (LVDS or LVPECL) and state (active or high impedance) of each individual output can also be controlled with the I2C
interface after power up.
Table 3H. Power-up Default Settings
FSEL1
FSEL0
Frequency
PLL State
(On or Bypass)
Output State
(Active or High Impedance)
Output Style
(LVDS or LVPECL)
0 (default)
0 (default)
Frequency 0
PLL State 0
Output State 0
Output Style 0
0
1
Frequency 1
PLL State 1
Output State 1
Output Style 1
1
0
Frequency 2
PLL State 2
Output State 2
Output Style 2
1
1
Frequency 3
PLL State 3
Output State 3
Output Style 3
Serial Interface Configuration Description
The IDT8T49N004I has an I2C-compatible configuration interface to
access any of the internal registers (Table 3B) for frequency and PLL
parameter programming. The IDT8T49N004I acts as a slave device
on the I2C bus and has the address 0b1101110. The interface
accepts byte-oriented block write and block read operations. An
address byte (P) specifies the register address (Table 3B) as the byte
position of the first register to write or read. Data bytes (registers) are
accessed in sequential order from the lowest to the highest byte
(most significant bit first, see Table 3I, 3J).
Read and write block transfers can be stopped after any complete
byte transfer. It is recommended to terminate the I2C read or write
transfer after accessing byte #23 by sending a stop command.
For full electrical I2C compliance, it is recommended to use external
pull-up resistors for SDATA and SCLK. The internal pull-up resistors
have a size of 50k typical.
Table 3I. Block Write Operation
Bit
Description
1
2:8
9
10
11:18
19
20:27
28
29-36
37
...
...
...
START
Slave Address
W (0)
ACK
Address Byte P
ACK
Data Byte
(P)
ACK
Data Byte
(P+1)
ACK
Data Byte
...
ACK
STOP
1
7
1
1
8
1
8
1
8
1
8
1
1
Length (bits)
Table 3J. Block Read Operation
Bit
1
2:8
9
10
11:18
19
20
21:27
28
29
30:37
38
39-46
47
...
...
...
START
Slave
Address
W
(0)
A
C
K
Address
byte P
A
C
K
Repeated
START
Slave
Address
R
(1)
A
C
K
Data Byte
(P)
A
C
K
Data Byte
(P+1)
A
C
K
Data Byte
...
A
C
K
STOP
1
7
1
1
8
1
1
7
1
1
8
1
8
1
8
1
1
Description
Length (bits)
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
9
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
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
Rating
Supply Voltage, VCC
3.63V
Inputs, VI
XTAL_IN
Other Input
0V to 2V
-0.5V to VCC + 0.5V
Outputs, IO (LVPECL)
Continuous Current
Surge Current
50mA
100mA
Outputs, IO (SDATA)
10mA
Outputs, IO (LVDS)
Continuous Current
Surge Current
10mA
15mA
Package Thermal Impedance, JA
33.1C/W (0 mps)
Storage Temperature, TSTG
-65C to 150C
DC Electrical Characteristics
Table 4A. Power Supply DC Characteristics, VCC = VCCO = 3.3V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VCC
Core Supply Voltage
VCCA
Test Conditions
Minimum
Typical
Maximum
Units
3.135
3.3
3.465
V
Analog Supply Voltage
VCC – 0.32
3.3
VCC
V
VCCO
Output Supply Voltage
3.135
3.3
3.465
V
ICCA
Analog Supply Current
32
mA
IEE
Power Supply Current
LVPECL
192
mA
ICC
Power Supply Current
LVDS
125
mA
ICCO
Output Supply Current
LVDS
85
mA
Table 4B. Power Supply DC Characteristics, VCC = VCCO = 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VCC
Core Supply Voltage
VCCA
Minimum
Typical
Maximum
Units
2.375
2.5
2.625
V
Analog Supply Voltage
VCC – 0.28
2.5
VCC
V
VCCO
Output Supply Voltage
2.375
2.5
2.625
V
ICCA
Analog Supply Current
28
mA
IEE
Power Supply Current
LVPECL
184
mA
ICC
Power Supply Current
LVDS
122
mA
ICCO
Output Supply Current
LVDS
82
mA
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
Test Conditions
10
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 4C. LVCMOS/LVTTL DC Characteristics, VCC = VCCO = 3.3V ± 5% or 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VIH
Input High
Voltage
VIL
Input Low
Voltage
Test Conditions
Minimum
SCLK, SDATA,
CLK_SEL, FSEL[1:0]
VCC = 3.3V
Maximum
Units
2
VCC + 0.3
V
VCC = 2.5V
1.7
VCC + 0.3
V
SCLK, SDATA, CLK_SEL
VCC = 3.3V
-0.3
0.8
V
SCLK, SDATA, CLK_SEL
VCC = 2.5V
-0.3
0.7
V
VCC = 3.3V or 2.5V
0.5
V
FSEL[1:0]
Typical
Input
High Current
SCLK, SDATA
VCC = VIN = 3.465V or 2.625V
5
µA
IIH
CLK_SEL, FSEL[1:0]
VCC = VIN = 3.465V or 2.625V
150
µA
Input
Low Current
SCLK, SDATA
VCC = 3.465V or 2.625V, VIN = 0V
-150
µA
IIL
CLK_SEL, FSEL[1:0]
VCC = 3.465V or 2.625V, VIN = 0V
-5
µA
Output
High Voltage;
NOTE 1
LOCK
VCCO = 3.465V
2.6
V
VOH
LOCK
VCCO = 2.625V
1.8
V
VOL
Output
Low Voltage;
NOTE 1
LOCK
VCCO = 3.465V or 2.625V
0.5
V
NOTE 1: Outputs terminated with 50 to VCCO/2. In the Parameter Measurement Information Section, see Output Load Test Circuit Diagrams.
Table 4D. Differential DC Characteristics, VCC = VCCO = 3.3V ± 5% or 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
Test Conditions
IIH
Input
High Current
IIL
Input
Low Current
VPP
Peak-to-Peak Voltage
0.15
1.3
V
VCMR
Common Mode Input Voltage;
NOTE 1
VEE
VCC – 0.85
V
Maximum
Units
CLK, nCLK
Minimum
Typical
VCC = VIN = 3.465V or 2.625V
Maximum
Units
150
µA
nCLK
VCC = 3.465V or 2.625V, VIN = 0V
-150
µA
CLK
VCC = 3.465V or 2.625V, VIN = 0V
-5
µA
NOTE 1: Common mode input voltage is at the cross point.
Table 4E. LVPECL DC Characteristics, VCC = VCCO = 3.3V±5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
Test Conditions
Minimum
Typical
VOH
Output High Voltage; NOTE 1
VCCO – 1.1
VCCO – 0.75
V
VOL
Output Low Voltage; NOTE 1
VCCO – 2.0
VCCO – 1.6
V
VSWING
Peak-to-Peak Output Voltage Swing
0.6
1.0
V
NOTE 1: Outputs termination with 50 to VCCO – 2V.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
11
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Table 4F. LVPECL DC Characteristics, VCC = VCCO = 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VOH
Output High Voltage; NOTE 1
VOL
Output Low Voltage; NOTE 1
VSWING
Peak-to-Peak Output Voltage Swing
Test Conditions
Minimum
Typical
Maximum
Units
VCCO – 1.2
VCCO – 0.75
V
VCCO – 2.0
VCCO – 1.5
V
0.5
1.0
V
NOTE 1: Outputs termination with 50 to VCCO – 2V.
Table 4G. LVDS DC Characteristics, VCC = VCCO = 3.3V±5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VOD
Differential Output Voltage
VOD
VOD Magnitude Change
VOS
Offset Voltage
VOS
VOS Magnitude Change
Test Conditions
Minimum
Typical
Maximum
Units
247
345
454
mV
50
mV
1.375
V
50
mV
1.15
1.25
Table 4H. LVDS DC Characteristics, VCC = VCCO = 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Symbol
Parameter
VOD
Differential Output Voltage
VOD
VOD Magnitude Change
VOS
Offset Voltage
VOS
VOS Magnitude Change
Test Conditions
Minimum
Typical
Maximum
Units
230
340
454
mV
50
mV
1.375
V
50
mV
Maximum
Units
1.15
1.25
Table 5. Crystal Characteristics
Parameter
Test Conditions
Minimum
Mode of Oscillation
Typical
Fundamental
Frequency
10
40
MHz
Load Capacitance (CL)
10
18
pF
50
Equivalent Series Resistance (ESR)
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
12
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
AC Electrical Characteristics
Table 6A. PCI Express Jitter Specifications, VCC = VCCO = 3.3V ± 5% or 2.5V ± 5%, VEE = 0V, TA = -40°C to 85°C
Typical
Maximum
PCIe Industry
Specification
Units
ƒ = 100MHz, 25MHz Crystal Input
Evaluation Band: 0Hz - Nyquist
(clock frequency/2)
8.3
13.2
86
ps
Phase Jitter RMS;
NOTE 2, 4
ƒ = 100MHz, 25MHz Crystal Input
High Band: 1.5MHz - Nyquist
(clock frequency/2)
0.78
1.35
3.1
ps
tREFCLK_LF_RMS
(PCIe Gen 2)
Phase Jitter RMS;
NOTE 2, 4
ƒ = 100MHz, 25MHz Crystal Input
Low Band: 10kHz - 1.5MHz
0.05
0.10
3.0
ps
tREFCLK_RMS
(PCIe Gen 3)
Phase Jitter RMS;
NOTE 3, 4
ƒ = 100MHz, 25MHz Crystal Input
Evaluation Band: 0Hz - Nyquist
(clock frequency/2)
0.175
0.34
0.8
ps
Symbol
Parameter
tj
(PCIe Gen 1)
Phase Jitter
Peak-to-Peak;
NOTE 1, 4
tREFCLK_HF_RMS
(PCIe Gen 2)
Test Conditions
Minimum
NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is
mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium
has been reached under these conditions. For additional information, refer to the PCI Express Application Note section in the datasheet.
NOTE 1: Peak-to-Peak jitter after applying system transfer function for the Common Clock Architecture. Maximum limit for PCI Express Gen 1
is 86ps peak-to-peak for a sample size of 106 clock periods.
NOTE 2: RMS jitter after applying the two evaluation bands to the two transfer functions defined in the Common Clock Architecture and
reporting the worst case results for each evaluation band. Maximum limit for PCI Express Generation 2 is 3.1ps RMS for tREFCLK_HF_RMS
(High Band) and 3.0ps RMS for tREFCLK_LF_RMS (Low Band).
NOTE 3: RMS jitter after applying system transfer function for the common clock architecture. This specification is based on the PCI Express
Base Specification Revision 0.7, October 2009 and is subject to change pending the final release version of the specification.
NOTE 4: This parameter is guaranteed by characterization. Not tested in production.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
13
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Table 6B. AC Characteristics, VCC = VCCO = 3.3V ± 5% or 2.5V ± 5% VEE = 0V, TA = -40°C to 85°
Symbol
Parameter
fDIFF_IN
Differential Input Frequency
fVCO
VCO Frequency
tjit(Ø)
Test Conditions
RMS Phase Jitter, Random;
NOTE 1
Minimum
Typical
Maximum
Units
10
312.5
MHz
1910
2500
MHz
25MHz Crystal, fOUT = 100MHz,
Integration Range:
12kHz – 20MHz
258
332
fs
25MHz Crystal, fOUT = 125MHz,
Integration Range: 12kHz –
20MHz
220
291
fs
25MHz Crystal, fOUT = 125MHz,
Integration Range: 10kHz –
1MHz
164
232
fs
25MHz Crystal, fOUT =
156.25MHz, Integration Range:
12kHz – 20MHz
228
306
fs
25MHz Crystal, fOUT =
156.25MHz, Integration Range:
10kHz – 1MHz
175
234
fs
25MHz Crystal, fOUT = 250MHz,
Integration Range: 12kHz –
20MHz
212
292
fs
30.72MHz Crystal, fOUT =
491.52MHz, Integration Range:
12kHz – 20MHz
213
299
fs
19.44MHz Crystal, fOUT =
622.08MHz, Integration Range:
12kHz – 20MHz
280
386
fs
tsk(o)
Output Skew;
NOTE 2, 3
LVPECL Outputs
LVDS_SEL = 0
45
ps
LVDS Outputs
LVDS_SEL = 1
45
ps
t R / tF
Output
Rise/Fall Time
LVPECL Outputs
20% - 80%, LVDS_SEL = 0
100
400
ps
LVDS Outputs
20% - 80%, LVDS_SEL = 1
100
400
ps
N > 3 Output Divider;
LVDS_SEL = 0 or 1
47
53
%
N 3 Output Divider;
LVDS_SEL = 0 or 1
42
58
%
odc
Output Duty Cycle
tLOCK
PLL Lock Time;
NOTE 3, 4
LOCK Output
20
ms
tTRANSITION
Transition
Time;
NOTE 3, 4
LOCK Output
20
ms
NOTE: Electrical parameters are guaranteed over the specified ambient operating temperature range, which is established when the device is
mounted in a test socket with maintained transverse airflow greater than 500 lfpm. The device will meet specifications after thermal equilibrium
has been reached under these conditions.
NOTE 1: Refer to Phase Noise Plots.
NOTE 2: Defined as skew between outputs at the same supply voltage and with equal load conditions. Measured at the differential
crosspoints.
NOTE 3: These parameters are guaranteed by characterization. Not tested in production.
NOTE 4: Refer to tLOCK and tTRANSITION in Parameter Measurement Information.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
14
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Noise Power (dBc/Hz)
Typical Phase Noise at 100MHz (3.3V)
Offset Frequency (Hz)
Noise Power (dBc/Hz)
Typical Phase Noise at 125MHz (3.3V)
Offset Frequency (Hz)
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
15
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Noise Power (dBc/Hz)
Typical Phase Noise at 156.25MHz (3.3V)
Offset Frequency (Hz)
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
16
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Parameter Measurement Information
2V
2V
2V
VCC,
VCCO
2V
VCC,
VCCO
VCCA
-1.3V ± 0.165V
VCCA
-0.5V ± 0.125V
3.3V LVPECL Output Load AC Test Circuit
2.5V LVPECL Output Load AC Test Circuit
SCOPE
3.3V ±5%
VCC,
VCCO
2.5V±5%
POWER SUPPLY
+ Float GND –
VCCA
VCC,
VCCO
Qx
VCCA
nQx
3.3V LVDS Output Load AC Test Circuit
2.5V LVDS Output Load AC Test Circuit
VCC
nCLK
CLK
VEE
Differential Input Levels
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
RMS Phase Jitter
17
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Parameter Measurement Information, continued
nQ[0:3]
nQx
Q[0:3]
Qx
nQy
Qy
Output Skew
Output Duty Cycle/Pulse Width/Period
nQ[0:3]
nQ[0:3]
80%
80%
VOD
Q[0:3]
Q[0:3]
20%
20%
tF
tR
LVPECL Output Rise/Fall Time
LVDS Output Rise/Fall Time
Offset Voltage Setup
Differential Output Voltage Setup
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
18
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Parameter Measurement Information, continued
LockTime & Transition Time
Applications Information
Recommendations for Unused Input and Output Pins
Inputs:
Outputs:
LVCMOS Control Pins
LVPECL Outputs
All control pins have internal pullups or pulldowns; additional
resistance is not required but can be added for additional protection.
A 1k resistor can be used.
All unused LVPECL outputs can be left floating. We recommend that
there is no trace attached. Both sides of the differential output pair
should either be left floating or terminated.
CLK/nCLK Inputs
LVDS Outputs
For applications not requiring the use of the differential input, both
CLK and nCLK can be left floating. Though not required, but for
additional protection, a 1k resistor can be tied from CLK to ground.
All unused LVDS output pairs can be either left floating or terminated
with 100 across. If they are left floating, there should be no trace
attached.
Crystal Inputs
For applications not requiring the use of the crystal oscillator input,
both XTAL_IN and XTAL_OUT can be left floating. Though not
required, but for additional protection, a 1k resistor can be tied from
XTAL_IN to ground.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
19
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Wiring the Differential Input to Accept Single-Ended Levels
line impedance. For most 50 applications, R3 and R4 can be 100.
The values of the resistors can be increased to reduce the loading for
slower and weaker LVCMOS driver. When using single-ended
signaling, the noise rejection benefits of differential signaling are
reduced. Even though the differential input can handle full rail
LVCMOS signaling, it is recommended that the amplitude be
reduced. The datasheet specifies a lower differential amplitude,
however this only applies to differential signals. For single-ended
applications, the swing can be larger, however VIL cannot be less
than -0.3V and VIH cannot be more than VCC + 0.3V. Though some
of the recommended components might not be used, the pads
should be placed in the layout. They can be utilized for debugging
purposes. The datasheet specifications are characterized and
guaranteed by using a differential signal.
Figure 1 shows how a differential input can be wired to accept single
ended levels. The reference voltage V1= VCC/2 is generated by the
bias resistors R1 and R2. The bypass capacitor (C1) is used to help
filter noise on the DC bias. This bias circuit should be located as close
to the input pin as possible. The ratio of R1 and R2 might need to be
adjusted to position the V1 in the center of the input voltage swing.
For example, if the input clock swing is 2.5V and VCC = 3.3V, R1 and
R2 value should be adjusted to set V1 at 1.25V. The values below are
for when both the single ended swing and VCC are at the same
voltage. This configuration requires that the sum of the output
impedance of the driver (Ro) and the series resistance (Rs) equals
the transmission line impedance. In addition, matched termination at
the input will attenuate the signal in half. This can be done in one of
two ways. First, R3 and R4 in parallel should equal the transmission
Figure 1. Recommended Schematic for Wiring a Differential Input to Accept Single-ended Levels
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
20
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Overdriving the XTAL Interface
can be done in one of two ways. First, R1 and R2 in parallel should
equal the transmission line impedance. For most 50 applications,
R1 and R2 can be 100. This can also be accomplished by removing
R1 and changing R2 to 50. The values of the resistors can be
increased to reduce the loading for a slower and weaker LVCMOS
driver. Figure 2B shows an example of the interface diagram for an
LVPECL driver. This is a standard LVPECL termination with one side
of the driver feeding the XTAL_IN input. It is recommended that all
components in the schematics be placed in the layout. Though some
components might not be used, they can be utilized for debugging
purposes. The datasheet specifications are characterized and
guaranteed by using a quartz crystal as the input.
The XTAL_IN input can be overdriven by an LVCMOS driver or by one
side of a differential driver through an AC coupling capacitor. The
XTAL_OUT pin can be left floating. The amplitude of the input signal
should be between 500mV and 1.8V and the slew rate should not be
less than 0.2V/nS. For 3.3V LVCMOS inputs, the amplitude must be
reduced from full swing to at least half the swing in order to prevent
signal interference with the power rail and to reduce internal noise.
Figure 2A shows an example of the interface diagram for a high
speed 3.3V LVCMOS driver. This configuration requires that the sum
of the output impedance of the driver (Ro) and the series resistance
(Rs) equals the transmission line impedance. In addition, matched
termination at the crystal input will attenuate the signal in half. This
Figure 2A. General Diagram for LVCMOS Driver to XTAL Input Interface
Figure 2B. General Diagram for LVPECL Driver to XTAL Input Interface
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
3.3V Differential Clock Input Interface
interfaces suggested here are examples only. If the driver is from
another vendor, use their termination recommendation. Please
consult with the vendor of the driver component to confirm the driver
termination requirements.
The CLK /nCLK accepts LVDS, LVPECL, HCSL and other differential
signals. Both VSWING and VOH must meet the VPP and VCMR input
requirements. Figures 3A to 3D show interface examples for the
CLK/nCLK input driven by the most common driver types. The input
3.3V
3.3V
3.3V
3.3V
3.3V
Zo = 50Ω
CLK
CLK
Zo = 50Ω
nCLK
R1
50Ω
Differential
Input
LVPECL
Differential
Input
LVPECL
nCLK
R2
50Ω
R2
50Ω
Figure 3A. CLK/nCLK Input Driven by a
3.3V LVPECL Driver
Figure 3B. CLK/nCLK Input Driven by a
3.3V LVPECL Driver
3.3V
3.3V
3.3V
3.3V
Zo = 50Ω
*R3
CLK
CLK
R1
100Ω
nCLK
HCSL
*R4
Zo = 50Ω
Differential
Input
LVDS
Figure 3C. CLK/nCLK Input Driven by a
3.3V HCSL Driver
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
nCLK
Receiver
Figure 3D. CLK/nCLK Input Driven by a 3.3V LVDS Driver
22
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
2.5V Differential Clock Input Interface
interfaces suggested here are examples only. If the driver is from
another vendor, use their termination recommendation. Please
consult with the vendor of the driver component to confirm the driver
termination requirements.
The CLK /nCLK accepts LVDS, LVPECL, HCSL and other differential
signals. Both VSWING and VOH must meet the VPP and VCMR input
requirements. Figures 4A to 4D show interface examples for the
CLK/nCLK input driven by the most common driver types. The input
2.5V
2.5V
2.5V
2.5V
2.5V
R3
250
R4
250
Zo = 50
CLK
Zo = 50
CLK
Zo = 50
nCLK
Zo = 50
nCLK
R1
62.5
R1
50
Differential
Input
LVPECL
R2
62.5
Differential
Input
LVPECL
R2
50
R3
18
Figure 4A. CLK/nCLK Input Driven by a
2.5V LVPECL Driver
Figure 4B. CLK/nCLK Input Driven by a
2.5V LVPECL Driver
2.5V
2.5V
2.5V
2.5V
*R3
33
Zo = 50
Zo = 50
CLK
CLK
R1
100
Zo = 50
nCLK
HCSL
*R4
33
R1
50
R2
50
Zo = 50
Differential
Input
LVDS
nCLK
Differential
Input
*Optional – R3 and R4 can be 0
Figure 4C. CLK/nCLK Input Driven by a
2.5V HCSL Driver
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
Figure 4D. CLK/nCLK Input Driven by a 2.5V LVDS Driver
23
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
LVDS Driver Termination
standard termination schematic as shown in Figure 5A can be used
with either type of output structure. Figure 5B, which can also be
used with both output types, is an optional termination with center tap
capacitance to help filter common mode noise. The capacitor value
should be approximately 50pF. If using a non-standard termination, it
is recommended to contact IDT and confirm if the output structure is
current source or voltage source type. In addition, since these
outputs are LVDS compatible, the input receiver’s amplitude and
common-mode input range should be verified for compatibility with
the output.
For a general LVDS interface, the recommended value for the
termination impedance (ZT) is between 90 and 132. The actual
value should be selected to match the differential impedance (Z0) of
your transmission line. A typical point-to-point LVDS design uses a
100 parallel resistor at the receiver and a 100 differential
transmission-line environment. In order to avoid any
transmission-line reflection issues, the components should be
surface mounted and must be placed as close to the receiver as
possible. IDT offers a full line of LVDS compliant devices with two
types of output structures: current source and voltage source. The
Termination for 3.3V LVPECL Outputs
transmission lines. Matched impedance techniques should be used
to maximize operating frequency and minimize signal distortion.
Figures 6A and 6B show two different layouts which are
recommended only as guidelines. Other suitable clock layouts may
exist and it would be recommended that the board designers
simulate to guarantee compatibility across all printed circuit and clock
component process variations.
The clock layout topology shown below is a typical termination for
LVPECL outputs. The two different layouts mentioned are
recommended only as guidelines.
The differential outputs are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, terminating
resistors (DC current path to ground) or current sources must be
used for functionality. These outputs are designed to drive 50
Figure 6A. 3.3V LVPECL Output Termination
R3
125
3.3V
R4
125
3.3V
3.3V
Zo = 50
+
_
LVPECL
Input
Zo = 50
R1
84
R2
84
Figure 6B. 3.3V LVPECL Output Termination
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Termination for 2.5V LVPECL Outputs
level. The R3 in Figure 7B can be eliminated and the termination is
shown in Figure 7C.
Figure 7A and Figure 9B show examples of termination for 2.5V
LVPECL driver. These terminations are equivalent to terminating 50
to VCCO – 2V. For VCCO = 2.5V, the VCCO – 2V is very close to ground
2.5V
VCCO = 2.5V
2.5V
2.5V
VCCO = 2.5V
R1
250
R3
250
50
+
50
+
50
–
50
2.5V LVPECL Driver
–
R1
50
2.5V LVPECL Driver
R2
62.5
R2
50
R4
62.5
R3
18
Figure 7A. 2.5V LVPECL Driver Termination Example
Figure 7B. 2.5V LVPECL Driver Termination Example
2.5V
VCCO = 2.5V
50
+
50
–
2.5V LVPECL Driver
R1
50
R2
50
Figure 7C. 2.5V LVPECL Driver Termination Example
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
25
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
VFQFN EPAD Thermal Release Path
and dependent upon the package power dissipation as well as
electrical conductivity requirements. Thus, thermal and electrical
analysis and/or testing are recommended to determine the minimum
number needed. Maximum thermal and electrical performance is
achieved when an array of vias is incorporated in the land pattern. It
is recommended to use as many vias connected to ground as
possible. It is also recommended that the via diameter should be 12
to 13mils (0.30 to 0.33mm) with 1oz copper via barrel plating. This is
desirable to avoid any solder wicking inside the via during the
soldering process which may result in voids in solder between the
exposed pad/slug and the thermal land. Precautions should be taken
to eliminate any solder voids between the exposed heat slug and the
land pattern. Note: These recommendations are to be used as a
guideline only. For further information, please refer to the Application
Note on the Surface Mount Assembly of Amkor’s Thermally/
Electrically Enhance Leadframe Base Package, Amkor Technology.
In order to maximize both the removal of heat from the package and
the electrical performance, a land pattern must be incorporated on
the Printed Circuit Board (PCB) within the footprint of the package
corresponding to the exposed metal pad or exposed heat slug on the
package, as shown in Figure 6. The solderable area on the PCB, as
defined by the solder mask, should be at least the same size/shape
as the exposed pad/slug area on the package to maximize the
thermal/electrical performance. Sufficient clearance should be
designed on the PCB between the outer edges of the land pattern
and the inner edges of pad pattern for the leads to avoid any shorts.
While the land pattern on the PCB provides a means of heat transfer
and electrical grounding from the package to the board through a
solder joint, thermal vias are necessary to effectively conduct from
the surface of the PCB to the ground plane(s). The land pattern must
be connected to ground through these vias. The vias act as “heat
pipes”. The number of vias (i.e. “heat pipes”) are application specific
PIN
PIN PAD
SOLDER
EXPOSED HEAT SLUG
GROUND PLANE
THERMAL VIA
SOLDER
LAND PATTERN
(GROUND PAD)
PIN
PIN PAD
Figure 6. P.C. Assembly for Exposed Pad Thermal Release Path – Side View (drawing not to scale)
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
26
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
PCI Express Application Note
PCI Express jitter analysis methodology models the system
response to reference clock jitter. The block diagram below shows the
most frequently used Common Clock Architecture in which a copy of
the reference clock is provided to both ends of the PCI Express Link.
In the jitter analysis, the transmit (Tx) and receive (Rx) serdes PLLs
are modeled as well as the phase interpolator in the receiver. These
transfer functions are called H1, H2, and H3 respectively. The overall
system transfer function at the receiver is:
Ht s = H3 s H1 s – H2 s
The jitter spectrum seen by the receiver is the result of applying this
system transfer function to the clock spectrum X(s) and is:
Y s = X s H3 s H1 s – H2 s
In order to generate time domain jitter numbers, an inverse Fourier
Transform is performed on X(s)*H3(s) * [H1(s) - H2(s)].
PCIe Gen 2A Magnitude of Transfer Function
PCI Express Common Clock Architecture
For PCI Express Gen 1, one transfer function is defined and the
evaluation is performed over the entire spectrum: DC to Nyquist (e.g
for a 100MHz reference clock: 0Hz – 50MHz) and the jitter result is
reported in peak-peak.
PCIe Gen 2B Magnitude of Transfer Function
For PCI Express Gen 3, one transfer function is defined and the
evaluation is performed over the entire spectrum. The transfer
function parameters are different from Gen 1 and the jitter result is
reported in RMS.
PCIe Gen 1 Magnitude of Transfer Function
For PCI Express Gen 2, two transfer functions are defined with 2
evaluation ranges and the final jitter number is reported in RMS. The
two evaluation ranges for PCI Express Gen 2 are 10kHz – 1.5MHz
(Low Band) and 1.5MHz – Nyquist (High Band). The plots show the
individual transfer functions as well as the overall transfer function Ht.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
PCIe Gen 3 Magnitude of Transfer Function
For a more thorough overview of PCI Express jitter analysis
methodology, please refer to IDT Application Note PCI Express
Reference Clock Requirements.
27
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Schematic Layout
In order to achieve the best possible filtering, it is recommended that
the placement of the filter components be on the device side of the
PCB as close to the power pins as possible. If space is limited, the
0.1uF capacitor in each power pin filter should be placed on the
device side of the PCB and the other components can be placed on
the opposite side.
Figure 9 shows an example of IDT8T49N004I application schematic.
The schematic focuses on functional connections and is not
configuration specific. Refer to the pin description and functional
tables in the datasheet to ensure that the logic control inputs are
properly set.
In this example, the device is operated at VCC = VCCO = VCCA = 3.3V
rather than 2.5V. The CLK, nCLK inputs are provided by a 3.3V
LVPECL driver and depicted with a Y-termination rather than the
standard four resistor VCC-2V Thevinin termination for reasons of
minimum termination power and layout simplicity. Three examples of
PECL terminations are shown for the outputs to demonstrate some
of the design options available with LVPECL.
Power supply filter recommendations are a general guideline to be
used for reducing external noise from coupling into the devices. The
VCC and VCCO filters start to attenuate noise at approximately 10kHz.
If a specific frequency noise component is known, such as switching
power supply frequencies, it is recommended that component values
be adjusted and if required, additional filtering be added. Additionally,
good general design practices for power plane voltage stability
suggests adding bulk capacitances in the local area of all devices.
As with any high speed analog circuitry, the power supply pins are
vulnerable to noise. To achieve optimum jitter performance, power
supply isolation is required. The IDT8T49N004I provides separate
power supplies to isolate from coupling into the internal PLL.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
The schematic example focuses on functional connections and is not
configuration specific. Refer to the pin description and functional
tables in the datasheet to ensure the logic control inputs are properly
set.
28
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Figure 9. IDT8T49N004I Application Schematic
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
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©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
LVPECL Power Considerations
This section provides information on power dissipation and junction temperature for the IDT8T49N004I.
Equations and example calculations are also provided.
1.
Power Dissipation.
The total power dissipation for the IDT8T49N004I is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for VCC = 3.465V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
•
Power (core)MAX = VCC_MAX * IEE_MAX = 3.465V * 192mA = 665.28mW
•
Power (outputs)MAX = 31.55mW/Loaded Output pair
If all outputs are loaded, the total power is 4 * 31.55mW = 126.2mW
Total Power_MAX (3.465V, with all outputs switching) = 665.28W + 126.2mW = 791.48W
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad directly affects the reliability of the device. The
maximum recommended junction temperature is 125°C. Limiting the internal transistor junction temperature, Tj, to 125°C ensures that the bond
wire and bond pad temperature remains below 125°C.
The equation for Tj is as follows: Tj = JA * Pd_total + TA
Tj = Junction Temperature
JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
TA = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance JA must be used. Assuming no air flow and
a multi-layer board, the appropriate value is 33.1°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.791W * 33.1°C/W = 111.2°C. This is below the limit of 125°C.
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow and the type of
board (multi-layer).
Table 7. Thermal Resistance JA for 32-Lead VFQFN, Forced Convection
JA by Velocity
Meters per Second
Multi-Layer PCB, JEDEC Standard Test Boards
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
0
1
3
33.1°C/W
28.1°C/W
25.4°C/W
30
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
3. Calculations and Equations.
The purpose of this section is to calculate the power dissipation for the LVPECL output pair.
LVPECL output driver circuit and termination are shown in Figure 12.
VCCO
Q1
VOUT
RL
50Ω
VCCO - 2V
Figure 10. LVPECL Driver Circuit and Termination
To calculate worst case power dissipation into the load, use the following equations which assume a 50 load, and a termination voltage of
VCCO – 2V.
•
For logic high, VOUT = VOH_MAX = VCCO_MAX – 0.75V
(VCCO_MAX – VOH_MAX) = 0.75V
•
For logic low, VOUT = VOL_MAX = VCCO_MAX – 1.6V
(VCCO_MAX – VOL_MAX) = 1.6V
Pd_H is power dissipation when the output drives high.
Pd_L is the power dissipation when the output drives low.
Pd_H = [(VOH_MAX – (VCCO_MAX – 2V))/RL] * (VCCO_MAX – VOH_MAX) = [(2V – (VCCO_MAX – VOH_MAX))/RL] * (VCCO_MAX – VOH_MAX) =
[(2V – 0.75V)/50] * 0.75V = 18.75mW
Pd_L = [(VOL_MAX – (VCCO_MAX – 2V))/RL] * (VCCO_MAX – VOL_MAX) = [(2V – (VCCO_MAX – VOL_MAX))/RL] * (VCCO_MAX – VOL_MAX) =
[(2V – 1.6V)/50] * 1.6V = 12.80mW
Total Power Dissipation per output pair = Pd_H + Pd_L = 31.55mW
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
31
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
LVDS Power Considerations
This section provides information on power dissipation and junction temperature for the IDT8T49N004I.
Equations and example calculations are also provided.
1.
Power Dissipation.
The total power dissipation for the IDT8T49N004I is the sum of the core power plus the analog power plus the power dissipated in the load(s).
The following is the power dissipation for VCC = 3.3V +5% = 3.465V, which gives worst case results.
•
Power (core)MAX = VDD_MAX * (IDD_MAX + IDDA_MAX) = 3.465V * (125mA + 32mA) = 544mW
•
Power (outputs)MAX = VDDO_MAX * IDDO_MAX = 3.465V * 85mA = 294.525mW
Total Power_MAX = 544mW + 294.525mW = 876.645mW
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad directly affects the reliability of the device. The
maximum recommended junction temperature is 125°C. Limiting the internal transistor junction temperature, Tj, to 125°C ensures that the bond
wire and bond pad temperature remains below 125°C.
The equation for Tj is as follows: Tj = JA * Pd_total + TA
Tj = Junction Temperature
JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
TA = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance JA must be used. Assuming no air flow and
a multi-layer board, the appropriate value is 33.1°C/W per Table 8 below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
85°C + 0.877W * 33.1°C/W = 112.8°C. This is below the limit of 125°C.
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow and the type of
board (multi-layer).
Table 8. Thermal Resistance JA for 32-Lead VFQFN, Forced Convection
JA by Velocity
Meters per Second
Multi-Layer PCB, JEDEC Standard Test Boards
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
0
1
3
33.1°C/W
28.1°C/W
25.4°C/W
32
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
Reliability Information
Table 9. JA vs. Air Flow Table for a 32-Lead VFQFN
JA vs. Air Flow
Meters per Second
Multi-Layer PCB, JEDEC Standard Test Boards
0
1
3
33.1°C/W
28.1°C/W
25.4°C/W
Transistor Count
The transistor count for IDT8T49N004I is: 26,856
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
33
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
32-Lead VFQFN Package Outline and Dimensions
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
34
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Ordering Information
Table 10. Ordering Information
Part/Order Number
8T49N004A-dddNLGI
8T49N004A-dddNLGI8
Marking
Package
IDT8T49N004A-dddNLGI “Lead-Free” 32-Lead VFQFN
IDT8T49N004A-dddNLGI “Lead-Free” 32-Lead VFQFN
Shipping Packaging
Tray
Tape & Reel
Temperature
-40C to 85C
-40C to 85C
NOTE: For the specific -ddd order codes, refer to the document Programmable FemtoClock® NG Product Ordering Guide.
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
35
©2013 Integrated Device Technology, Inc.
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
IDT8T49N004I Data Sheet
Revision History Sheet
Rev
Table
Page
Description of Change
9, 35
Changed name of the IDT8T49N00xI Programmable FemtoClock® NG Product Ordering
Information document to Programmable FemtoClock® Ordering Product Information
Deleted quantity from Tape & Reel, Deleted Lead Free note.
8/20/2013
Changed title to Programmable FemtoClock® NG LVPECL/LVDS Clock Generator with
4-Outputs.
Changed text from ‘Programmable FemtoClock® Ordering Product Information’ to
‘Programmable FemtoClock® NG Product Ordering Guide’.
Changed Note from ‘Programmable FemtoClock® Ordering Product Information’ to
‘Programmable FemtoClock® NG Product Ordering Guide’.
9/26/13
changed the min load capacitance from 12pF to 10pF
10/22/13
A
T10
35
1
9
A
A
T10
35
T5
12
IDT8T49N004ANLGI REVISION A OCTOBER 15, 2013
Date
36
©2013 Integrated Device Technology, Inc.
IDT8T49N004I Data Sheet
PROGRAMMABLE FEMTOCLOCK® NG LVPECL/LVDS CLOCK GENERATOR WITH 4-OUTPUTS
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DISCLAIMER Integrated Device Technology, Inc. (IDT) and its subsidiaries reserve the right to modify the products and/or specifications described herein at any time and at IDT’s sole discretion. All information in this document,
including descriptions of product features and performance, is subject to change without notice. Performance specifications and the operating parameters of the described products are determined in the independent state and are not
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