TI1 LMK00308 3-ghz 8-output ultra-low additive jitter differential clock buffer/level translator Datasheet

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LMK00308
SNAS576D – FEBRUARY 2012 – REVISED MARCH 2016
LMK00308 3-GHz 8-Output Ultra-Low Additive Jitter
Differential Clock Buffer/Level Translator
1 Features
2 Applications
•
•
1
•
•
•
•
•
•
•
•
3:1 Input Multiplexer:
– Two Universal Inputs Operate up to 3.1 GHz
and Accept LVPECL, LVDS, CML, SSTL,
HSTL, HCSL, or Single-Ended Clocks
– One Crystal Input Accepts a 10 to 40 MHz
Crystal or Single-Ended Clock
Two Banks with 4 Differential Outputs Each:
– LVPECL, LVDS, HCSL, or Hi-Z (Selectable
Per Bank)
– LVPECL Additive Jitter with LMK03806 Clock
Source at 156.25 MHz:
– 20 fs RMS (10 kHz to 1 MHz)
– 51 fs RMS (12 kHz to 20 MHz)
High PSRR: -65 / -76 dBc (LVPECL/LVDS) at
156.25 MHz
LVCMOS Output with Synchronous Enable Input
Pin-Controlled Configuration
VCC Core Supply: 3.3 V ± 5%
3 Independent VCCO Output Supplies: 3.3 V/2.5 V
± 5%
Industrial Temperature Range: -40°C to +85°C
40-lead WQFN (6 mm × 6 mm)
•
•
•
Clock Distribution and Level Translation for ADCs,
DACs, Multi-Gigabit Ethernet, XAUI, Fibre
Channel, SATA/SAS, SONET/SDH, CPRI, HighFrequency Backplanes
Switches, Routers, Line Cards, Timing Cards
Servers, Computing, PCI Express (PCIe 3.0)
Remote Radio Units and Baseband Units
3 Description
The LMK00308 is a 3-GHz, 8-output differential
fanout buffer intended for high-frequency, low-jitter
clock/data distribution and level translation. The input
clock can be selected from two universal inputs or
one crystal input. The selected input clock is
distributed to two banks of 4 differential outputs and
one LVCMOS output. Both differential output banks
can be independently configured as LVPECL, LVDS,
or HCSL drivers, or disabled. The LVCMOS output
has a synchronous enable input for runt-pulse-free
operation when enabled or disabled. The LMK00308
operates from a 3.3 V core supply and 3 independent
3.3 V/2.5 V output supplies.
The LMK00308 provides high performance,
versatility, and power efficiency, making it ideal for
replacing fixed-output buffer devices while increasing
timing margin in the system.
Device Information(1)
PART NUMBER
PACKAGE
LMK00308
WQFN (40)
BODY SIZE (NOM)
6.00 mm × 6.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
4 Functional Block Diagram
CLKoutA_TYPE[1:0]
CLKin_SEL[1:0]
VCCOA VCCOB VCCOC
2
CLKoutA0
CLKoutA0*
CLKin0
Universal Inputs
(Differential/
Single-Ended)
CLKoutA3
CLKoutA3*
CLKin0*
CLKin1
3:1
MUX
CLKin1*
Crystal
LVPECL Output Swing (VOD) vs. Frequency
VCCOA
2
VCCOB
CLKoutB0
CLKoutB0*
OSCin
OSCout
CLKoutB_TYPE[1:0]
1.0
Bank A
4 Output Pairs
(LVPECL, LVDS,
HCSL, or Hi-Z)
2
CLKoutB3
CLKoutB3*
Bank B
4 Output Pairs
(LVPECL, LVDS,
HCSL, or Hi-Z)
VCCOC
REFout_EN
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.0
100
GND
Vcco=2.5 V, Rterm=91
Vcco=3.3 V, Rterm=160
0.1
REFout (LVCMOS)
SYNC
0.9
OUTPUT SWING (V)
VCC
1000
FREQUENCY (MHz)
10000
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LMK00308
SNAS576D – FEBRUARY 2012 – REVISED MARCH 2016
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Functional Block Diagram ....................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
7.1
7.2
7.3
7.4
7.5
7.6
1
1
1
1
2
4
6
Absolute Maximum Ratings ...................................... 6
ESD Ratings.............................................................. 6
Recommended Operating Conditions ...................... 6
Thermal Information .................................................. 6
Electrical Characteristics........................................... 7
Typical Characteristics ............................................ 14
8
Parameter Measurement Information ................ 18
9
Detailed Description ............................................ 19
8.1 Differential Voltage Measurement Terminology...... 18
9.1 Overview ................................................................. 19
9.2 Functional Block Diagram ....................................... 19
9.3 Feature Description................................................. 20
10 Application and Implementation........................ 22
10.1 Driving the Clock Inputs ........................................ 22
10.2 Crystal Interface .................................................... 23
10.3 Termination and Use of Clock Drivers .................. 24
11 Power Supply Recommendations ..................... 29
11.1 Power Supply Sequencing ....................................
11.2 Current Consumption and Power Dissipation
Calculations..............................................................
11.3 Power Supply Bypassing ......................................
11.4 Thermal Management ...........................................
29
29
31
32
12 Device and Documentation Support ................. 34
12.1
12.2
12.3
12.4
12.5
Documentation Support .......................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
34
34
34
34
34
13 Mechanical, Packaging, and Orderable
Information ........................................................... 34
5 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (May 2013) to Revision D
Page
•
Added " Ultra-Low Additive Jitter" to document title ............................................................................................................... 1
•
Added, updated, or renamed the following sections: Specifications; Detailed Description; Application and
Implementation; Power Supply Recommendations; Device and Documentation Support; Mechanical, Packaging,
and Ordering Information........................................................................................................................................................ 1
•
Changed Cin (typ) from 1 pF to 4 pF (based on updated test method) in Electrical Characteristics: Crystal Interface ........ 8
•
Added footnote for VI_SE parameter in the Electrical Characteristics table. .......................................................................... 8
•
Added “Additive RMS Jitter, Integration Bandwidth 10 kHz to 20 MHz” parameter with 100 MHz and 156.25 MHz
Test conditions, Typical values, Max values, and footnotes in Electrical Characteristics: LVPECL Outputs ....................... 9
•
Added “Additive RMS Jitter, Integration Bandwidth 10 kHz to 20 MHz” parameter with 100 MHz and 156.25 MHz
Test conditions, Typical values, Max values, and footnotes in Electrical Characteristics: LVDS Outputs .......................... 10
•
Added new paragraph at end of Driving the Clock Inputs.................................................................................................... 22
•
Changed part number in Figure 27 and Figure 28 to "LMK00308" ..................................................................................... 23
•
Changed Cin = 4 pF (typ, based on updated test method) in Crystal Interface .................................................................. 23
•
Added Power Supply Sequencing ....................................................................................................................................... 29
Changes from Revision B (February 2013) to Revision C
Page
•
Changed Target Applications by adding additional applications to the second and third bullets, and removing HighSpeed and Serial Interfaces from first bullet. ......................................................................................................................... 1
•
Changed VCM text to condition for VIH to VCM parameter group. ............................................................................................ 8
•
Deleted VIH min value from Electrical Characteristics table. .................................................................................................. 8
•
Deleted VIL max value from Electrical Characteristics table................................................................................................... 8
•
Added VI_SE parameter and spec limits with corresponding table note to Electrical Characteristics Table. .......................... 8
•
Changed third paragraph in Driving the Clock Inputs section to include CLKin* and LVCMOS text. Revised to better
correspond with information in Electrical Characteristics Table ........................................................................................... 22
•
Changed bypass cap text to signal attenuation text of the fourth paragraph in Driving the Clock Inputs section. .............. 22
2
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•
Changed Single-Ended LVCMOS Input, DC Coupling with Common Mode Biasing image with revised graphic............... 23
•
Added text to second paragraph of Termination for AC Coupled Differential Operation to explain graphic update to
Differential LVDS Operation with AC Coupling to Receivers. .............................................................................................. 26
•
Changed graphic for Differential LVDS Operation, AC Coupling, No Biasing by the Receiver and updated caption. ........ 26
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6 Pin Configuration and Functions
GND
CLKoutA_TYPE1
REFout_EN
VCCOC
REFout
VCC
CLKin1
CLKin1*
CLKoutB_TYPE1
GND
40-Pin WQFN
Package RTA
Top View
40
39
38
37
36
35
34
33
32
31
CLKoutA0
1
30
CLKoutB0
CLKoutA0*
2
29
CLKoutB0*
VCCOA
3
28
VCCOB
CLKoutA1
4
27
CLKoutB1
CLKoutA1*
5
26
CLKoutB1*
Top Down View
4
VCCOA
6
25
VCCOB
CLKoutA2
7
24
CLKoutB2
CLKoutA2*
8
23
CLKoutB2*
CLKoutA3
9
22
CLKoutB3
CLKoutA3*
10
21
CLKoutB3*
12
13
14
15
16
17
18
19
VCC
OSCin
OSCout
CLKin_SEL0
CLKin0
CLKin0*
CLKin_SEL1
CLKoutB_TYPE0
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20
GND
11
CLKoutA_TYPE0
DAP
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Pin Functions (1)
PIN
NO.
NAME
TYPE
DESCRIPTION
DAP
DAP
GND
1, 2
CLKoutA0, CLKoutA0*
O
Die Attach Pad. Connect to the PCB ground plane for heat dissipation.
3, 6
VCCOA
PWR
4, 5
CLKoutA1, CLKoutA1*
O
Differential clock output A1. Output type set by CLKoutA_TYPE pins.
Differential clock output A0. Output type set by CLKoutA_TYPE pins.
Power supply for Bank A Output buffers. VCCOA can operate from 3.3 V or
2.5 V. The VCCOA pins are internally tied together. Bypass with a 0.1 uF
low-ESR capacitor placed very close to each Vcco pin. (2)
7, 8
CLKoutA2, CLKoutA2*
O
Differential clock output A2. Output type set by CLKoutA_TYPE pins.
9, 10
CLKoutA3, CLKoutA3*
O
Differential clock output A3. Output type set by CLKoutA_TYPE pins.
11, 39
CLKoutA_TYPE0, CLKoutA_TYPE1
I
Bank A output buffer type selection pins
12, 35
Vcc
PWR
13
OSCin
I
Input for crystal. Can also be driven by a XO, TCXO, or other external
single-ended clock.
14
OSCout
O
Output for crystal. Leave OSCout floating if OSCin is driven by a singleended clock.
15, 18
CLKin_SEL0, CLKin_SEL1
I
Clock input selection pins
16, 17
CLKin0, CLKin0*
I
Universal clock input 0 (differential/single-ended)
19, 32
CLKoutB_TYPE0, CLKoutB_TYPE1
I
Bank B output buffer type selection pins
20, 31, 40
GND
GND
21, 22
CLKoutB3*, CLKoutB3
O
Differential clock output B3. Output type set by CLKoutB_TYPE pins.
23, 24
CLKoutB2*, CLKoutB2
O
Differential clock output B2. Output type set by CLKoutB_TYPE pins.
25, 28
VCCOB
PWR
26, 27
CLKoutB1*, CLKoutB1
O
Differential clock output B1. Output type set by CLKoutB_TYPE pins.
29, 30
CLKoutB0*, CLKoutB0
O
Differential clock output B0. Output type set by CLKoutB_TYPE pins.
33, 34
CLKin1*, CLKin1
I
Universal clock input 1 (differential/single-ended)
36
REFout
O
LVCMOS reference output. Enable output by pulling REFout_EN pin high.
37
VCCOC
PWR
Power supply for REFout Output buffer. VCCOC can operate from 3.3 V or
2.5 V. Bypass with a 0.1 uF low-ESR capacitor placed very close to each
Vcco pin. (2)
38
REFout_EN
I
REFout enable input. Enable signal is internally synchronized to selected
clock input. (3)
(1)
(2)
(3)
(3)
Power supply for Core and Input buffer blocks. The Vcc supply operates
from 3.3 V. Bypass with a 0.1 uF low-ESR capacitor placed very close to
each Vcc pin.
(3)
(3)
Ground
Power supply for Bank B Output buffers. VCCOB can operate from 3.3 V or
2.5 V. The VCCOB pins are internally tied together. Bypass with a 0.1 uF
low-ESR capacitor placed very close to each Vcco pin. (2)
Any unused output pins should be left floating with minimum copper length (see note in Clock Outputs), or properly terminated if
connected to a transmission line, or disabled/Hi-Z if possible. See Clock Outputs for output configuration or Termination and Use of
Clock Drivers output interface and termination techniques.
The output supply voltages/pins (VCCOA, VCCOB, and VCCOC) will be referred to generally as VCCO when no distinction is needed, or
when the output supply can be inferred by the output bank/type.
CMOS control input with internal pull-down resistor.
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2)
MIN
MAX
UNIT
VCC, VCCO
Supply voltages
-0.3
3.6
V
VIN
Input voltage
-0.3
(VCC + 0.3)
V
TSTG
Storage temperature
-65
+150
°C
TL
Lead temperature (solder 4 s)
+260
°C
TJ
Junction temperature
+150
°C
(1)
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
7.2 ESD Ratings
VALUE
V(ESD) (1)
(1)
(2)
(3)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (2)
±2000
Machine model (MM)
±150
Charged-device model (CDM), per JEDEC specification JESD22C101 (3)
±750
UNIT
V
Handling and assembly of this device should only be done at ESD-free workstations.
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 500-V HBM is possible with the necessary precautions. Pins listed as ±2000 V may actually have higher performance.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Manufacturing with
less than 250-V CDM is possible with the necessary precautions. Pins listed as ±750 V may actually have higher performance.
7.3 Recommended Operating Conditions
TA
Ambient Temperature Range
TJ
Junction Temperature
VCC
Core Supply Voltage Range
Output Supply Voltage Range (1)
VCCO
(1)
(2)
(2)
MIN
TYP
MAX
-40
25
85
UNIT
°C
125
°C
3.15
3.3
3.45
V
3.3 – 5%
2.5 – 5%
3.3
2.5
3.3 + 5%
2.5 + 5%
V
The output supply voltages/pins (VCCOA, VCCOB, and VCCOC) will be referred to generally as VCCO when no distinction is needed, or
when the output supply can be inferred by the output bank/type.
Vcco should be less than or equal to Vcc (Vcco ≤ Vcc).
7.4 Thermal Information
LMK00308
THERMAL METRIC
(1) (2)
RTA (WQFN)
UNIT
40 PINS
RθJA
Junction-to-ambient thermal resistance
31.4
RθJC(top) (DAP)
Junction-to-case (top) thermal resistance
7.2
(1)
(2)
6
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
Specification assumes 9 thermal vias connect the die attach pad (DAP) to the embedded copper plane on the 4-layer JEDEC board.
These vias play a key role in improving the thermal performance of the package. It is recommended that the maximum number of vias
be used in the board layout.
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7.5 Electrical Characteristics
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
CLKinX selected
8.5
10.5
mA
OSCin selected
CURRENT CONSUMPTION (3)
ICC_CORE
Core Supply Current, All
Outputs Disabled
10
13.5
mA
ICC_PECL
Additive Core Supply
Current, Per LVPECL
Bank Enabled
20
26.5
mA
ICC_LVDS
Additive Core Supply
Current, Per LVDS
Bank Enabled
25
30.5
mA
ICC_HCSL
Additive Core Supply
Current, Per HCSL
Bank Enabled
31
38.5
mA
ICC_CMOS
Additive Core Supply
Current, LVCMOS
Output Enabled
3.5
5.5
mA
ICCO_PECL
Additive Output Supply
Current, Per LVPECL
Bank Enabled
132
160
mA
ICCO_LVDS
Additive Output Supply
Current, Per LVDS
Bank Enabled
26
34.5
mA
ICCO_HCSL
Additive Output Supply
Current, Per HCSL
Bank Enabled
Includes Output Bank Bias and Load Currents,
RT = 50 Ω on all outputs in bank
68
84
mA
Additive Output Supply
Current, LVCMOS
Output Enabled
Vcco = 3.3 V ± 5%
9
10
mA
ICCO_CMOS
200 MHz, CL = 5 pF
Vcco = 2.5 V ± 5%
7
8
mA
Includes Output Bank Bias and Load Currents, RT
= 50 Ω to Vcco - 2V on all outputs in bank
POWER SUPPLY RIPPLE REJECTION (PSRR)
PSRRPECL
Ripple-Induced Phase
Spur Level Differential
LVPECL Output (4)
PSRRLVDS
Ripple-Induced Phase
Spur Level Differential
LVDS Output (4)
PSRRHCSL
Ripple-Induced Phase
Spur Level Differential
HCSL Output (4)
100 kHz, 100 mVpp
Ripple Injected on Vcco,
Vcco = 2.5 V
156.25 MHz
-65
312.5 MHz
-63
156.25 MHz
-76
312.5 MHz
-74
156.25 MHz
-72
312.5 MHz
-63
dBc
dBc
dBc
CMOS CONTROL INPUTS (CLKin_SELn, CLKoutX_TYPEn, REFout_EN)
VIH
High-Level Input Voltage
1.6
Vcc
VIL
Low-Level Input Voltage
GND
0.4
V
IIH
High-Level Input Current VIH = Vcc, Internal pull-down resistor
50
µA
IIL
Low-Level Input Current
(1)
(2)
(3)
(4)
VIL = 0 V, Internal pull-down resistor
-5
0.1
V
µA
The output supply voltages/pins (VCCOA, VCCOB, and VCCOC) will be referred to generally as VCCO when no distinction is needed, or
when the output supply can be inferred by the output bank/type.
The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
See Power Supply Recommendations for more information on current consumption and power dissipation calculations.
Power supply ripple rejection, or PSRR, is defined as the single-sideband phase spur level (in dBc) modulated onto the clock output
when a single-tone sinusoidal signal (ripple) is injected onto the Vcco supply. Assuming no amplitude modulation effects and small index
modulation, the peak-to-peak deterministic jitter (DJ) can be calculated using the measured single-sideband phase spur level (PSRR) as
follows: DJ (ps pk-pk) = [ (2 * 10(PSRR / 20)) / (π * fCLK) ] * 1E12
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
3.1
GHz
Vcc
V
CLOCK INPUTS (CLKin0/CLKin0*, CLKin1/CLKin1*)
Functional up to 3.1 GHz
Output frequency range and timing specified per
output type (refer to LVPECL, LVDS, HCSL,
LVCMOS output specifications)
fCLKin
Input Frequency
Range (5)
VIHD
Differential Input High
Voltage
VILD
Differential Input Low
Voltage
VID
Differential Input Voltage
Swing (6)
VCMD
Differential Input
Common Mode Voltage
VIH
Single-Ended Input High
Voltage
VIL
Single-Ended Input Low
Voltage
VI_SE
Single-Ended Input
Voltage Swing (7) (8)
VCM
Single-Ended Input
Common Mode Voltage
ISOMUX
CLKin driven differentially
DC
GND
V
0.15
1.3
VID = 150 mV
0.25
Vcc - 1.2
VID = 350 mV
0.25
Vcc - 1.1
VID = 800 mV
0.25
Vcc - 0.9
Vcc
CLKinX driven single-ended (AC or DC coupled),
CLKinX* AC coupled to GND or externally biased
within VCM range
Mux Isolation, CLKin0 to fOFFSET > 50 kHz,
CLKin1
PCLKinX = 0 dBm
GND
V
V
V
V
0.3
2
0.25
Vcc - 1.2
fCLKin0 = 100 MHz
-84
fCLKin0 = 200 MHz
-82
fCLKin0 = 500 MHz
-71
fCLKin0 = 1000 MHz
-65
Vpp
V
dBc
CRYSTAL INTERFACE (OSCin, OSCout)
FCLK
External Clock
Frequency Range
FXTAL
Crystal Frequency
Range
CIN
OSCin Input
Capacitance
(5)
(6)
(7)
(8)
(9)
8
(5)
OSCin driven single-ended, OSCout floating
Fundamental mode crystal
ESR ≤ 200 Ω (10 to 30 MHz)
ESR ≤ 125 Ω (30 to 40 MHz)
(9)
10
4
250
MHz
40
MHz
pF
Specification is ensured by characterization and is not tested in production.
See Differential Voltage Measurement Terminology for definition of VID and VOD voltages.
Parameter is specified by design, not tested in production.
For clock input frequency ≥ 100 MHz, CLKinX can be driven with single-ended (LVCMOS) input swing up to 3.3 Vpp. For clock input
frequency < 100 MHz, the single-ended input swing should be limited to 2 Vpp max to prevent input saturation (refer to Driving the Clock
Inputs for interfacing 2.5 V/3.3 V LVCMOS clock input < 100 MHz to CLKinX).
The ESR requirements stated must be met to ensure that the oscillator circuitry has no startup issues. However, lower ESR values for
the crystal may be necessary to stay below the maximum power dissipation (drive level) specification of the crystal. Refer to Crystal
Interface for crystal drive level considerations.
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
Vcco = 3.3 V ± 5%,
RT = 160 Ω to GND
1.0
1.2
Vcco = 2.5 V ± 5%,
RT = 91 Ω to GND
0.75
1.0
Vcco = 3.3 V ± 5%,
RT = 160 Ω to GND
1.5
3.1
Vcco = 2.5 V ± 5%,
RT = 91 Ω to GND
1.5
2.3
MAX
UNIT
LVPECL OUTPUTS (CLKoutAn/CLKoutAn*, CLKoutBn/CLKoutBn*)
fCLKout_FS
fCLKout_RS
JitterADD
JitterADD
JitterADD
Noise Floor
DUTY
Maximum Output
Frequency Full VOD
Swing (5) (10)
VOD ≥ 600 mV,
RL = 100 Ω differential
Maximum Output
Frequency Reduced
VOD Swing (5) (10)
VOD ≥ 400 mV,
RL = 100 Ω differential
Additive RMS Jitter,
Integration Bandwidth
10 kHz to 20
MHz (5) (11) (12)
Vcco = 2.5 V ± 5%:
RT = 91 Ω to GND,
Vcco = 3.3 V ± 5%:
RT = 160 Ω to GND,
RL = 100 Ω differential
Additive RMS Jitter
Integration Bandwidth
1 MHz to 20 MHz (11)
Additive RMS Jitter with
LVPECL clock source
from LMK03806 (11) (13)
Noise Floor
fOFFSET ≥ 10 MHz (14) (15)
Duty Cycle (5)
VOH
Output High Voltage
VOL
Output Low Voltage
VOD
Vcco = 3.3 V,
RT = 160 Ω to GND,
RL = 100 Ω differential
Output Voltage Swing
Vcco = 3.3 V,
RT = 160 Ω to GND,
RL = 100 Ω differential
Vcco = 3.3 V,
RT = 160 Ω to GND,
RL = 100 Ω differential
GHz
GHz
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
77
98
CLKin: 156.25 MHz,
Slew rate ≥ 3 V/ns
54
78
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
59
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
64
CLKin: 625 MHz,
Slew rate ≥ 3 V/ns
30
CLKin: 156.25 MHz,
JSOURCE = 190 fs RMS
(10 kHz to 1 MHz)
20
CLKin: 156.25 MHz,
JSOURCE = 195 fs RMS
(12 kHz to 20 MHz)
51
fs
fs
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
-162.5
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
-158.1
CLKin: 625 MHz,
Slew rate ≥ 3 V/ns
-154.4
50% input clock duty cycle
TA = 25 °C, DC Measurement,
RT = 50 Ω to Vcco - 2 V
(6)
fs
45%
dBc/Hz
55%
Vcco 1.2
Vcco 0.9
Vcco 0.7
V
Vcco 2.0
Vcco 1.75
Vcco 1.5
V
600
830
1000
mV
(10) See Typical Characteristics for output operation over frequency.
(11) For the 100 MHz and 156.25 MHz clock input conditions, Additive RMS Jitter (JADD) is calculated using Method #1: JADD = SQRT(JOUT2
- JSOURCE2), where JOUT is the total RMS jitter measured at the output driver and JSOURCE is the RMS jitter of the clock source applied to
CLKin. For the 625 MHz clock input condition, Additive RMS Jitter is approximated using Method #2: JADD = SQRT(2*10dBc/10) /
(2*π*fCLK), where dBc is the phase noise power of the Output Noise Floor integrated from 1 to 20 MHz bandwidth. The phase noise
power can be calculated as: dBc = Noise Floor + 10*log10(20 MHz - 1 MHz). The additive RMS jitter was approximated for 625 MHz
using Method #2 because the RMS jitter of the clock source was not sufficiently low enough to allow practical use of Method #1. Refer
to the “Noise Floor vs. CLKin Slew Rate” and “RMS Jitter vs. CLKin Slew Rate” plots in Typical Characteristics.
(12) 100 MHz and 156.25 MHz input source from Rohde & Schwarz SMA100A Low-Noise Signal Generator and Sine-to-Square-wave
Conversion block.
(13) 156.25 MHz LVPECL clock source from LMK03806 with 20 MHz crystal reference (crystal part number: ECS-200-20-30BU-DU).
JSOURCE = 190 fs RMS (10 kHz to 1 MHz) and 195 fs RMS (12 kHz to 20 MHz). Refer to the LMK03806 datasheet for more information.
(14) The noise floor of the output buffer is measured as the far-out phase noise of the buffer. Typically this offset is ≥ 10 MHz, but for lower
frequencies this measurement offset can be as low as 5 MHz due to measurement equipment limitations.
(15) Phase noise floor will degrade as the clock input slew rate is reduced. Compared to a single-ended clock, a differential clock input
(LVPECL, LVDS) will be less susceptible to degradation in noise floor at lower slew rates due to its common mode noise rejection.
However, it is recommended to use the highest possible input slew rate for differential clocks to achieve optimal noise floor performance
at the device outputs.
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
tR
Output Rise Time
20% to 80% (7)
tF
Output Fall Time
80% to 20% (7)
TEST CONDITIONS
MIN
RT = 160 Ω to GND, Uniform transmission line up
to 10 in.with 50-Ω characteristic impedance, RL =
100 Ω differential, CL ≤ 5 pF
TYP
MAX
UNIT
175
300
ps
175
300
ps
LVDS OUTPUTS (CLKoutAn/CLKoutAn*, CLKoutBn/CLKoutBn*)
fCLKout_FS
Maximum Output
Frequency
Full VOD Swing (5) (10)
VOD ≥ 250 mV, RL = 100 Ω differential
1.0
1.6
GHz
fCLKout_RS
Maximum Output
Frequency
Reduced VOD
Swing (5) (10)
VOD ≥ 200 mV, RL = 100 Ω differential
1.5
2.1
GHz
JitterADD
Additive RMS Jitter,
Integration Bandwidth
10 kHz to 20
MHz (5) (11) (12)
JitterADD
Noise Floor
Additive RMS Jitter
Integration Bandwidth
1 MHz to 20 MHz (11)
Noise Floor
fOFFSET ≥ 10 MHz (14) (15)
DUTY
Duty Cycle (5)
VOD
Output Voltage Swing (6)
ΔVOD
Change in Magnitude of
VOD for Complementary
Output States
VOS
Output Offset Voltage
ΔVOS
Change in Magnitude of
VOS for Complementary
Output States
ISA
ISB
Output Short Circuit
Current Single Ended
ISAB
Output Short Circuit
Current Differential
tR
Output Rise Time
20% to 80% (7)
tF
Output Fall Time
80% to 20% (7)
10
RL = 100 Ω differential
Vcco = 3.3 V,
RL = 100 Ω differential
Vcco = 3.3 V,
RL = 100 Ω differential
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
94
115
CLKin: 156.25 MHz,
Slew rate ≥ 3 V/ns
70
90
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
89
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
77
CLKin: 625 MHz,
Slew rate ≥ 3 V/ns
37
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
-159.5
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
-157.0
CLKin: 625 MHz,
Slew rate ≥ 3 V/ns
-152.7
fs
50% input clock duty cycle
45%
250
1.125
dBc/Hz
55%
400
-50
TA = 25 °C, DC Measurement,
RL = 100 Ω differential
fs
1.25
450
mV
50
mV
1.375
V
-35
35
mV
TA = 25 °C,
Single ended outputs shorted to GND
-24
24
mA
Complementary outputs tied together
-12
12
mA
175
300
ps
175
300
ps
Uniform transmission line up to 10 inches with 50Ω characteristic impedance, RL = 100 Ω differential,
CL ≤ 5 pF
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
400
MHz
0.15
ps
HCSL OUTPUTS (CLKoutAn/CLKoutAn*, CLKoutBn/CLKoutBn*)
fCLKout
Output Frequency
Range (5)
RL = 50 Ω to GND, CL ≤ 5 pF
JitterADD_PCIe
Additive RMS Phase
Jitter for PCIe 3.0 (5)
PCIe Gen 3,
PLL BW = 2–5 MHz,
CDR = 10 MHz
JitterADD
Additive RMS Jitter
Integration Bandwidth
1 MHz to 20 MHz (11)
Vcco = 3.3 V,
RT = 50 Ω to GND
Noise Floor
fOFFSET ≥ 10 MHz (14) (15)
Vcco = 3.3 V,
RT = 50 Ω to GND
DUTY
Duty Cycle (5)
50% input clock duty cycle
VOH
Output High Voltage
VOL
Output Low Voltage
VCROSS
Absolute Crossing
Voltage (5) (16)
Noise Floor
ΔVCROSS
Total Variation of
VCROSS (5) (16)
tR
Output Rise Time
20% to 80% (7) (16)
tF
Output Fall Time
80% to 20% (7) (16)
DC
CLKin: 100 MHz,
Slew rate ≥ 0.6 V/ns
0.03
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
77
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
86
fs
CLKin: 100 MHz,
Slew rate ≥ 3 V/ns
-161.3
CLKin: 156.25 MHz,
Slew rate ≥ 2.7 V/ns
-156.3
TA = 25 °C, DC Measurement, RT = 50 Ω to GND
dBc/Hz
45%
55%
520
810
920
mV
-150
0.5
150
mV
160
350
460
mV
140
mV
300
500
ps
300
500
ps
RL = 50 Ω to GND, CL ≤ 5 pF
250 MHz, Uniform transmission line up to 10
inches with 50-Ω characteristic impedance, RL = 50
Ω to GND, CL ≤ 5 pF
(16) AC timing parameters for HCSL or CMOS are dependent on output capacitive loading.
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
250
MHz
LVCMOS OUTPUT (REFout)
fCLKout
Output Frequency
Range (5)
CL ≤ 5 pF
JitterADD
Additive RMS Jitter
Integration Bandwidth
1 MHz to 20 MHz (11)
Vcco = 3.3 V, CL ≤ 5 pF
100 MHz, Input Slew
rate ≥ 3 V/ns
95
Noise Floor
Noise Floor
fOFFSET ≥ 10 MHz (14) (15)
Vcco = 3.3 V, CL ≤ 5 pF
100 MHz, Input Slew
rate ≥ 3 V/ns
-159.3
DUTY
Duty Cycle (5)
50% input clock duty cycle
VOH
Output High Voltage
VOL
Output Low Voltage
IOH
DC
tR
Output Rise Time
20% to 80% (7) (16)
tF
Output Fall Time
80% to 20% (7) (16)
tEN
Output Enable Time (17)
tDIS
Output Disable Time (17)
55%
V
0.1
Vo = Vcco / 2
Output Low Current
(Sink)
dBc/Hz
Vcco 0.1
1 mA load
Output High Current
(Source)
IOL
45%
fs
Vcco = 3.3 V
28
Vcco = 2.5 V
20
Vcco = 3.3 V
28
Vcco = 2.5 V
20
250 MHz, Uniform transmission line up to 10
inches with 50-Ω characteristic impedance,
RL = 50 Ω to GND, CL ≤ 5 pF
CL ≤ 5 pF
V
mA
mA
225
400
ps
225
400
ps
3
cycles
3
cycles
(17) Output Enable Time is the number of input clock cycles it takes for the output to be enabled after REFout_EN is pulled high. Similarly,
Output Disable Time is the number of input clock cycles it takes for the output to be disabled after REFout_EN is pulled low. The
REFout_EN signal should have an edge transition much faster than that of the input clock period for accurate measurement.
12
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Electrical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V ± 5%, Vcco = 3.3 V ± 5%, 2.5 V ± 5%, -40 °C ≤ TA ≤ 85 °C, CLKin driven
differentially, input slew rate ≥ 3 V/ns. Typical values represent most likely parametric norms at Vcc = 3.3 V, Vcco = 3.3 V, TA
= 25 °C, and at the Recommended Operation Conditions at the time of product characterization and are not ensured. (1) (2)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
PROPAGATION DELAY and OUTPUT SKEW
tPD_PECL
Propagation Delay
CLKin-to-LVPECL (7)
RT = 160 Ω to GND, RL = 100 Ω differential,
CL ≤ 5 pF
180
360
540
ps
tPD_LVDS
Propagation Delay
CLKin-to-LVDS (7)
RL = 100 Ω differential, CL ≤ 5 pF
200
400
600
ps
tPD_HCSL
Propagation Delay
CLKin-to-HCSL (7) (16)
RT = 50 Ω to GND, CL ≤ 5 pF
295
590
885
ps
tPD_CMOS
Propagation Delay
CL ≤ 5 pF
CLKin-to-LVCMOS (7) (16)
Vcco = 3.3 V
900
1475
2300
Vcco = 2.5 V
1000
1550
2700
tSK(O)
Output Skew
LVPECL/LVDS/HCSL
30
50
ps
80
120
ps
tSK(PP)
(5) (16) (18)
Part-to-Part Output
Skew
LVPECL/LVDS/HCSL
Skew specified between any two CLKouts with the
same buffer type. Load conditions per output type
are the same as propagation delay specifications.
ps
(7) (16) (18)
(18) Output skew is the propagation delay difference between any two outputs with identical output buffer type and equal loading while
operating at the same supply voltage and temperature conditions.
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7.6 Typical Characteristics
Unless otherwise specified: Vcc = 3.3 V, Vcco = 3.3 V, TA = 25 °C, CLKin driven differentially, input slew rate ≥ 3 V/ns.
Consult Table 1 at the end of Typical Characteristics for graph notes.
1.0
0.45
Vcco=2.5 V, Rterm=91
Vcco=3.3 V, Rterm=160
0.40
0.8
OUTPUT SWING (V)
OUTPUT SWING (V)
0.9
0.7
0.6
0.5
0.4
0.3
0.20
0.15
0.10
0.05
0.00
1000
FREQUENCY (MHz)
10000
Figure 1. LVPECL Output Swing (VOD) vs. Frequency
100
0.4
0.6
0.3
0.4
0.2
0.2
0.0
-0.2
-0.4
-0.6
0.1
0.0
-0.1
-0.2
-0.4
2.5
5.0
TIME (ns)
7.5
10.0
Figure 3. LVPECL Output Swing @ 156.25 MHz
0.0
0.3
0.3
OUTPUT SWING (V)
0.4
0.2
0.1
0.0
-0.1
-0.2
2.5
5.0
TIME (ns)
7.5
10.0
Figure 4. LVDS Output Swing @ 156.25 MHz
0.4
-0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
0.00
10000
-0.3
-0.8
0.0
1000
FREQUENCY (MHz)
Figure 2. LVDS Output Swing (VOD) vs. Frequency
0.8
OUTPUT SWING (V)
OUTPUT SWING (V)
0.25
0.1
100
OUTPUT SWING (V)
0.30
0.2
0.0
-0.4
0.25
0.50
TIME (ns)
0.75
1.00
Figure 5. LVPECL Output Swing @ 1.5 GHz
14
0.35
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0.25
0.50
TIME (ns)
0.75
1.00
Figure 6. LVDS Output Swing @ 1.5 GHz
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Typical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V, Vcco = 3.3 V, TA = 25 °C, CLKin driven differentially, input slew rate ≥ 3 V/ns.
Consult Table 1 at the end of Typical Characteristics for graph notes.
1.0
1.00
OUTPUT SWING (V)
OUTPUT SWING (V)
0.8
0.6
0.4
0.2
0.0
1
2
3
TIME (ns)
4
LVPECL
LVDS
HCSL
LVCMOS
CLKin Source
-135
Fclk=100 MHz
Foffset=20 MHz
NOISE FLOOR (dBc/Hz)
NOISE FLOOR (dBc/Hz)
-0.50
-155
-160
-165
1
2
3
4
TIME (ns)
5
6
Figure 8. LVCMOS Output Swing @ 250 MHz
-170
-140
LVPECL
LVDS
HCSL
CLKin Source
Fclk=156.25 MHz
Foffset=20 MHz
-145
-150
-155
-160
-165
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
Figure 9. Noise Floor vs. CLKin Slew Rate @ 100 MHz
LVPECL
LVDS
CLKin Source
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
Figure 10. Noise Floor vs. CLKin Slew Rate @ 156.25 MHz
400
Fclk=625 MHz
Foffset=20 MHz
350
RMS JITTER (fs)
NOISE FLOOR (dBc/Hz)
0.00
-0.25
0
-150
-140
0.25
5
Figure 7. HCSL Output Swing @ 250 MHz
-135
0.50
-1.00
0
-145
load
load
-0.75
-0.2
-140
Vcco=3.3 V, AC coupled, 50
Vcco=2.5 V, AC coupled, 50
0.75
-145
-150
-155
300
LVPECL
LVDS
HCSL
LVCMOS
CLKin Source
Fclk=100 MHz
Int. BW=1-20 MHz
250
200
150
100
-160
50
-165
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
See Note 1 in Graph Notes table
Figure 11. Noise Floor vs. CLKin Slew Rate @ 625 MHz
Figure 12. RMS Jitter vs. CLKin Slew Rate @ 100 MHz
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Typical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V, Vcco = 3.3 V, TA = 25 °C, CLKin driven differentially, input slew rate ≥ 3 V/ns.
Consult Table 1 at the end of Typical Characteristics for graph notes.
450
RMS JITTER (fs)
400
LVPECL
LVDS
HCSL
CLKin Source
200
Fclk=156.25 MHz
Int. BW=1-20 MHz
LVPECL
LVDS
CLKin Source
175
RMS JITTER (fs)
500
350
300
250
200
150
Fclk=625 MHz
Int. BW=1-20 MHz
150
125
100
75
50
100
50
25
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
DIFFERENTIAL INPUT SLEW RATE (V/ns)
See Note 1 Graph Notes table.
-50
LVPECL
LVDS
HCSL
-55
Fclk=156.25 MHz
Vcco Ripple=100 mVpp
-60
-65
-70
-75
-80
-85
-90
.1
1
RIPPLE FREQUENCY (MHz)
10
Figure 15. PSRR vs. Ripple Frequency @ 156.25 MHz
750
650
LVPECL (0.35 ps/°C)
LVDS (0.35 ps/°C)
HCSL (0.35 ps/°C)
LVCMOS (2.2 ps/°C)
Right Y-axis plot
1850
1750
1650
450
1550
350
1450
-50
1350
-25
0
25
50
75
TEMPERATURE (°C)
LVPECL
LVDS
HCSL
-55
Fclk=312.5 MHz
Vcco Ripple=100 mVpp
-60
-65
-70
-75
-80
-85
-90
.1
1
RIPPLE FREQUENCY (MHz)
10
Figure 16. PSRR vs. Ripple Frequency @ 312.5 MHz
1950
550
250
-50
REFout PROPAGATION DELAY (ps)
CLKout PROPAGATION DELAY (ps)
850
Figure 14. RMS Jitter vs. CLKin Slew Rate @ 625 MHz
RIPPLE INDUCED SPUR LEVEL (dBc)
RIPPLE INDUCED SPUR LEVEL (dBc)
Figure 13. RMS Jitter vs. CLKin Slew Rate @ 156.25 MHz
100
See Note 1 in Graph Notes table
Figure 17. Propagation Delay vs. Temperature
16
Figure 18. LVPECL Phase Noise @ 100 MHz
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Typical Characteristics (continued)
Unless otherwise specified: Vcc = 3.3 V, Vcco = 3.3 V, TA = 25 °C, CLKin driven differentially, input slew rate ≥ 3 V/ns.
Consult Table 1 at the end of Typical Characteristics for graph notes.
See Note 1 in Graph Notes table
See Note 1 in Graph Notes table
200
Figure 20. HCSL Phase Noise @ 100 MHz
-60
20 MHz Crystal
40 MHz Crystal
175
PHASE NOISE (dBc/Hz)
CRYSTAL POWER DISSIPATION ( W)
Figure 19. LVDS Phase Noise @ 100 MHz
150
125
100
75
50
25
0
20 MHz Crystal, Rlim = 1.5 k
40 MHz Crystal, Rlim = 1.0 k
-80
-100
-120
-140
-160
-180
0
500 1k 1.5k 2k 2.5k 3k 3.5k 4k
RLIM( )
10
See Notes 2 and 3 in Graph Notes table
100
1k
10k 100k 1M
OFFSET FREQUENCY (Hz)
10M
See Notes 2 and 3 in Graph Notes table
Figure 21. Crystal Power Dissipation vs. RLIM
Figure 22. LVDS Phase Noise in Crystal Mode
Table 1. Graph Notes
NOTE
(1)
The typical RMS jitter values in the plots show the total output RMS jitter (JOUT) for each output buffer type and the source clock
RMS jitter (JSOURCE). From these values, the Additive RMS Jitter can be calculated as: JADD = SQRT(JOUT2 - JSOURCE2).
(2)
20 MHz crystal characteristics: Abracon ABL series, AT cut, CL = 18 pF , C0 = 4.4 pF measured (7 pF max), ESR = 8.5 Ω
measured (40 Ω max), and Drive Level = 1 mW max (100 µW typical).
(3)
40 MHz crystal characteristics: Abracon ABLS2 series, AT cut, CL = 18 pF , C0 = 5 pF measured (7 pF max), ESR = 5 Ω
measured (40 Ω max), and Drive Level = 1 mW max (100 µW typical).
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8 Parameter Measurement Information
8.1 Differential Voltage Measurement Terminology
The differential voltage of a differential signal can be described by two different definitions causing confusion
when reading datasheets or communicating with other engineers. This section will address the measurement and
description of a differential signal so that the reader will be able to understand and discern between the two
different definitions when used.
The first definition used to describe a differential signal is the absolute value of the voltage potential between the
inverting and non-inverting signal. The symbol for this first measurement is typically VID or VOD depending on if
an input or output voltage is being described.
The second definition used to describe a differential signal is to measure the potential of the non-inverting signal
with respect to the inverting signal. The symbol for this second measurement is VSS and is a calculated
parameter. Nowhere in the IC does this signal exist with respect to ground, it only exists in reference to its
differential pair. VSS can be measured directly by oscilloscopes with floating references, otherwise this value can
be calculated as twice the value of VOD as described in the first description.
Figure 23 illustrates the two different definitions side-by-side for inputs and Figure 24 illustrates the two different
definitions side-by-side for outputs. The VID (or VOD) definition show the DC levels, VIH and VOL (or VOH and VOL),
that the non-inverting and inverting signals toggle between with respect to ground. VSS input and output
definitions show that if the inverting signal is considered the voltage potential reference, the non-inverting signal
voltage potential is now increasing and decreasing above and below the non-inverting reference. Thus the peakto-peak voltage of the differential signal can be measured.
VID and VOD are often defined as volts (V) and VSS is often defined as volts peak-to-peak (VPP).
VID Definition
VSS Definition for Input
Non-Inverting Clock
VIH
VCM
VSS
VID
VIL
Inverting Clock
VSS = 2· VID
VID = | VIH ± VIL |
GND
Figure 23. Two Different Definitions for Differential Input Signals
VOD Definition
VSS Definition for Output
Non-Inverting Clock
VOH
VOS
VOL
VSS
VOD
Inverting Clock
VOD = | VOH - VOL |
VSS = 2· VOD
GND
Figure 24. Two Different Definitions for Differential Output Signals
Refer to Application Note AN-912 (literature number SNLA036), Common Data Transmission Parameters and
their Definitions, for more information.
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9 Detailed Description
9.1 Overview
The LMK00308 is an 8-output differential clock fanout buffer with low additive jitter that can operate up to 3.1
GHz. It features a 3:1 input multiplexer with an optional crystal oscillator input, two banks of 4 differential outputs
with multi-mode buffers (LVPECL, LVDS, HCSL, or Hi-Z), one LVCMOS output, and 3 independent output buffer
supplies. The input selection and output buffer modes are controlled via pin strapping. The device is offered in a
40-pin WQFN package and leverages much of the high-speed, low-noise circuit design employed in the
LMK04800 family of clock conditioners.
9.2 Functional Block Diagram
Functional Block Diagram
VCC
CLKoutA_TYPE[1:0]
CLKin_SEL[1:0]
VCCOA VCCOB VCCOC
2
VCCOA
2
CLKoutA0
CLKoutA0*
CLKin0
Universal Inputs
(Differential/
Single-Ended)
CLKoutA3
CLKoutA3*
CLKin0*
CLKin1
3:1
MUX
CLKin1*
Crystal
VCCOB
CLKoutB0
CLKoutB0*
OSCin
OSCout
CLKoutB_TYPE[1:0]
Bank A
4 Output Pairs
(LVPECL, LVDS,
HCSL, or Hi-Z)
2
CLKoutB3
CLKoutB3*
Bank B
4 Output Pairs
(LVPECL, LVDS,
HCSL, or Hi-Z)
VCCOC
REFout_EN
REFout (LVCMOS)
SYNC
GND
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9.3 Feature Description
9.3.1 VCC and VCCO Power Supplies
The LMK00308 has a 3.3 V core power supply (VCC) and 3 independent 3.3 V/2.5 V output power supplies
(VCCOA, VCCOB, VCCOC). Output supply operation at 2.5 V enables lower power consumption and output-level
compatibility with 2.5 V receiver devices. The output levels for LVPECL (VOH, VOL) and LVCMOS (VOH) are
referenced to the respective Vcco supply, while the output levels for LVDS and HCSL are relatively constant over
the specified Vcco range. Refer to Power Supply Recommendations for additional supply related considerations,
such as power dissipation, power supply bypassing, and power supply ripple rejection (PSRR).
NOTE
Care should be taken to ensure the Vcco voltages do not exceed the Vcc voltage to
prevent turning-on the internal ESD protection circuitry.
9.3.2 Clock Inputs
The input clock can be selected from CLKin0/CLKin0*, CLKin1/CLKin1*, or OSCin. Clock input selection is
controlled using the CLKin_SEL[1:0] inputs as shown in Table 2. Refer to Driving the Clock Inputs for clock input
requirements. When CLKin0 or CLKin1 is selected, the crystal circuit is powered down. When OSCin is selected,
the crystal oscillator circuit will start-up and its clock will be distributed to all outputs. Refer to Crystal Interface for
more information. Alternatively, OSCin may be be driven by a single-ended clock (up to 250 MHz) instead of a
crystal.
Table 2. Input Selection
CLKin_SEL1
CLKin_SEL0
SELECTED INPUT
0
0
CLKin0, CLKin0*
0
1
CLKin1, CLKin1*
1
X
OSCin
Table 3 shows the output logic state vs. input state when either CLKin0/CLKin0* or CLKin1/CLKin1* is selected.
When OSCin is selected, the output state will be an inverted copy of the OSCin input state.
Table 3. CLKin Input vs. Output States
20
STATE of
SELECTED CLKin
STATE of
ENABLED OUTPUTS
CLKinX and CLKinX*
inputs floating
Logic low
CLKinX and CLKinX*
inputs shorted together
Logic low
CLKin logic low
Logic low
CLKin logic high
Logic high
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9.3.3 Clock Outputs
The differential output buffer type for Bank A and Bank B outputs can be separately configured using the
CLKoutA_TYPE[1:0] and CLKoutB_TYPE[1:0] inputs, respectively, as shown in Table 4. For applications where
all differential outputs are not needed, any unused output pin should be left floating with a minimum copper
length (see note below) to minimize capacitance and potential coupling and reduce power consumption. If an
entire output bank will not be used, it is recommended to disable/Hi-Z the bank to reduce power. Refer to
Termination and Use of Clock Drivers for more information on output interface and termination techniques.
NOTE
For best soldering practices, the minimum trace length for any unused output pin should
extend to include the pin solder mask. This way during reflow, the solder has the same
copper area as connected pins. This allows for good, uniform fillet solder joints helping to
keep the IC level during reflow.
Table 4. Differential Output Buffer Type Selection
CLKoutX_
TYPE1
CLKoutX_
TYPE0
CLKoutX BUFFER TYPE
(BANK A or B)
0
0
LVPECL
0
1
LVDS
1
0
HCSL
1
1
Disabled (Hi-Z)
9.3.3.1 Reference Output
The reference output (REFout) provides a LVCMOS copy of the selected input clock. The LVCMOS output high
level is referenced to the Vcco voltage. REFout can be enabled or disabled using the enable input pin,
REFout_EN, as shown in Table 5.
Table 5. Reference Output Enable
REFout_EN
REFout STATE
0
Disabled (Hi-Z)
1
Enabled
The REFout_EN input is internally synchronized with the selected input clock by the SYNC block. This
synchronizing function prevents glitches and runt pulses from occurring on the REFout clock when enabled or
disabled. REFout will be enabled within 3 cycles (tEN) of the input clock after REFout_EN is toggled high. REFout
will be disabled within 3 cycles (tDIS) of the input clock after REFout_EN is toggled low.
When REFout is disabled, the use of a resistive loading can be used to set the output to a predetermined level.
For example, if REFout is configured with a 1 kΩ load to ground, then the output will be pulled to low when
disabled.
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10 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Driving the Clock Inputs
The LMK00308 has two universal inputs (CLKin0/CLKin0* and CLKin1/CLKin1*) that can accept AC- or DCcoupled 3.3V/2.5V LVPECL, LVDS, CML, SSTL, and other differential and single-ended signals that meet the
input requirements specified in the Electrical Characteristics. The device can accept a wide range of signals due
to its wide input common mode voltage range (VCM ) and input voltage swing (VID) / dynamic range. For 50% duty
cycle and DC-balanced signals, AC coupling may also be employed to shift the input signal to within the VCM
range. Refer to Termination and Use of Clock Drivers for signal interfacing and termination techniques.
To achieve the best possible phase noise and jitter performance, it is mandatory for the input to have high slew
rate of 3 V/ns (differential) or higher. Driving the input with a lower slew rate will degrade the noise floor and jitter.
For this reason, a differential signal input is recommended over single-ended because it typically provides higher
slew rate and common-mode-rejection. Refer to the “Noise Floor vs. CLKin Slew Rate” and “RMS Jitter vs. CLKin
Slew Rate” plots in Typical Characteristics.
While it is recommended to drive the CLKin/CLKin* pair with a differential signal input, it is possible to drive it
with a single-ended clock provided it conforms to the Single-Ended Input specifications for CLKin pins listed in
the Electrical Characteristics. For large single-ended input signals, such as 3.3V or 2.5V LVCMOS, a 50 Ω load
resistor should be placed near the input for signal attenuation to prevent input overdrive as well as for line
termination to minimize reflections. Again, the single-ended input slew rate should be as high as possible to
minimize performance degradation. The CLKin input has an internal bias voltage of about 1.4 V, so the input can
be AC coupled as shown in Figure 25. The output impedance of the LVCMOS driver plus Rs should be close to
50 Ω to match the characteristic impedance of the transmission line and load termination.
RS 0.1 PF
0.1 PF
50: Trace
50:
CMOS
Driver
LMK
Input
0.1 PF
Figure 25. Single-Ended LVCMOS Input, AC Coupling
A single-ended clock may also be DC coupled to CLKinX as shown in Figure 26. A 50-Ω load resistor should be
placed near the CLKinX input for signal attenuation and line termination. Because half of the single-ended swing
of the driver (VO,PP / 2) drives CLKinX, CLKinX* should be externally biased to the midpoint voltage of the
attenuated input swing ((VO,PP / 2) × 0.5). The external bias voltage should be within the specified input common
voltage (VCM) range. This can be achieved using external biasing resistors in the kΩ range (RB1 and RB2) or
another low-noise voltage reference. This will ensure the input swing crosses the threshold voltage at a point
where the input slew rate is the highest.
If the LVCMOS driver cannot achieve sufficient swing with a DC-terminated 50Ω load at the CLKinX input as
shown in Figure 26, then consider connecting the 50Ω load termination to ground through a capacitor (CAC). This
AC termination blocks the DC load current on the driver, so the voltage swing at the input is determined by the
voltage divider formed by the source (Ro+Rs) and 50Ω load resistors. The value for CAC depends on the trace
delay, Td, of the 50Ω transmission line, where CAC >= 3*Td/50Ω.
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Driving the Clock Inputs (continued)
CMOS
Driver
VO,PP
Rs
VO,PP/2
VCC
50: Trace
VBB ~ (VO,PP/2) x 0.5
50:
LMK
Input
RB1
VCC
RB2
0.1 PF
Figure 26. Single-Ended LVCMOS Input, DC Coupling
with Common Mode Biasing
If the crystal oscillator circuit is not used, it is possible to drive the OSCin input with an single-ended external
clock as shown in Figure 27. The input clock should be AC coupled to the OSCin pin, which has an internallygenerated input bias voltage, and the OSCout pin should be left floating. While OSCin provides an alternative
input to multiplex an external clock, it is recommended to use either differential input (CLKinX) since it offers
higher operating frequency, better common mode and power supply noise rejection, and greater performance
over supply voltage and temperature variations.
0.1 PF
50: Trace
OSCin
OSCout
LMK00308
RS 0.1 PF
50:
CMOS
Driver
Figure 27. Driving OSCin with a Single-Ended Input
10.2 Crystal Interface
C1
XTAL
RLIM
OSCin
OSCout
LMK00308
The LMK00308 has an integrated crystal oscillator circuit that supports a fundamental mode, AT-cut crystal. The
crystal interface is shown in Figure 28.
C2
Figure 28. Crystal Interface
The load capacitance (CL) is specific to the crystal, but usually on the order of 18 - 20 pF. While CL is specified
for the crystal, the OSCin input capacitance (CIN = 4 pF typical) of the device and PCB stray capacitance (CSTRAY
~ 1~3 pF) can affect the discrete load capacitor values, C1 and C2.
For the parallel resonant circuit, the discrete capacitor values can be calculated as follows:
CL = (C1 * C2) / (C1 + C2) + CIN + CSTRAY
(1)
Typically, C1 = C2 for optimum symmetry, so Equation 1 can be rewritten in terms of C1 only:
CL = C12 / (2 * C1) + CIN + CSTRAY
(2)
Finally, solve for C1:
C1 = (CL - CIN - CSTRAY)*2
(3)
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Crystal Interface (continued)
Electrical Characteristics provides crystal interface specifications with conditions that ensure start-up of the
crystal, but it does not specify crystal power dissipation. The designer will need to ensure the crystal power
dissipation does not exceed the maximum drive level specified by the crystal manufacturer. Overdriving the
crystal can cause premature aging, frequency shift, and eventual failure. Drive level should be held at a sufficient
level necessary to start-up and maintain steady-state operation.
The power dissipated in the crystal, PXTAL, can be computed by:
PXTAL = IRMS2 * RESR*(1 + C0/CL)2
where
•
•
•
•
IRMS is the RMS current through the crystal.
RESR is the max. equivalent series resistance specified for the crystal
CL is the load capacitance specified for the crystal
C0 is the min. shunt capacitance specified for the crystal
(4)
IRMS can be measured using a current probe (e.g. Tektronix CT-6 or equivalent) placed on the leg of the crystal
connected to OSCout with the oscillation circuit active.
As shown in Figure 28, an external resistor, RLIM, can be used to limit the crystal drive level, if necessary. If the
power dissipated in the selected crystal is higher than the drive level specified for the crystal with RLIM shorted,
then a larger resistor value is mandatory to avoid overdriving the crystal. However, if the power dissipated in the
crystal is less than the drive level with RLIM shorted, then a zero value for RLIM can be used. As a starting point, a
suggested value for RLIM is 1.5 kΩ.
10.3 Termination and Use of Clock Drivers
When terminating clock drivers keep in mind these guidelines for optimum phase noise and jitter performance:
• Transmission line theory should be followed for good impedance matching to prevent reflections.
• Clock drivers should be presented with the proper loads.
– LVDS outputs are current drivers and require a closed current loop.
– HCSL drivers are switched current outputs and require a DC path to ground via 50 Ω termination.
– LVPECL outputs are open emitter and require a DC path to ground.
• Receivers should be presented with a signal biased to their specified DC bias level (common mode voltage)
for proper operation. Some receivers have self-biasing inputs that automatically bias to the proper voltage
level; in this case, the signal should normally be AC coupled.
It is possible to drive a non-LVPECL or non-LVDS receiver with a LVDS or LVPECL driver as long as the above
guidelines are followed. Check the datasheet of the receiver or input being driven to determine the best
termination and coupling method to be sure the receiver is biased at the optimum DC voltage (common mode
voltage).
10.3.1 Termination for DC Coupled Differential Operation
For DC coupled operation of an LVDS driver, terminate with 100 Ω as close as possible to the LVDS receiver as
shown in Figure 29.
100: Trace
(Differential)
LVDS
Driver
100:
CLKoutX
LVDS
Receiver
CLKoutX*
Figure 29. Differential LVDS Operation, DC Coupling,
No Biasing by the Receiver
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Termination and Use of Clock Drivers (continued)
50:
For DC coupled operation of an HCSL driver, terminate with 50 Ω to ground near the driver output as shown in
Figure 30. Series resistors, Rs, may be used to limit overshoot due to the fast transient current. Because HCSL
drivers require a DC path to ground, AC coupling is not allowed between the output drivers and the 50 Ω
termination resistors.
Rs
CLKoutX
HCSL
Driver
HCSL
Receiver
50: Traces
Rs
50:
CLKoutX*
Figure 30. HCSL Operation, DC Coupling
For DC coupled operation of an LVPECL driver, terminate with 50 Ω to Vcco - 2 V as shown in Figure 31.
Alternatively terminate with a Thevenin equivalent circuit as shown in Figure 32 for Vcco (output driver supply
voltage) = 3.3 V and 2.5 V. In the Thevenin equivalent circuit, the resistor dividers set the output termination
voltage (VTT) to Vcco - 2 V.
50:
Vcco - 2V
CLKoutX
100: Trace
(Differential)
LVPECL
Driver
LVPECL
Receiver
50:
CLKoutX*
Vcco - 2V
Figure 31. Differential LVPECL Operation, DC Coupling
RPD
RPU
Vcco
CLKoutX
100: Trace
(Differential)
LVPECL
Driver
LVPECL
Receiver
RPD
VTT
120:
82:
~1.3V
2.5V
250:
62.5:
0.5V
RPD
RPU
3.3V
RPU
CLKoutX*
Vcco
Vcco
Figure 32. Differential LVPECL Operation, DC Coupling, Thevenin Equivalent
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Termination and Use of Clock Drivers (continued)
10.3.2 Termination for AC Coupled Differential Operation
AC coupling allows for shifting the DC bias level (common mode voltage) when driving different receiver
standards. Since AC coupling prevents the driver from providing a DC bias voltage at the receiver, it is important
to ensure the receiver is biased to its ideal DC level.
When driving differential receivers with an LVDS driver, the signal may be AC coupled by adding DC blocking
capacitors; however the proper DC bias point needs to be established at both the driver side and the receiver
side. The recommended termination scheme depends on whether the differential receiver has integrated
termination resistors or not.
When driving a differential receiver without internal 100 Ω differential termination, the AC coupling capacitors
should be placed between the load termination resistor and the receiver to allow a DC path for proper biasing of
the LVDS driver. This is shown in Figure 33. The load termination resistor and AC coupling capacitors should be
placed as close as possible to the receiver inputs to minimize stub length. The receiver can be biased internally
or externally to a reference voltage within the receiver’s common mode input range through resistors in the kiloohm range.
When driving a differential receiver with internal 100 Ω differential termination, a source termination resistor
should be placed before the AC coupling capacitors for proper DC biasing of the driver as shown in Figure 34.
However, with a 100 Ω resistor at the source and the load (i.e. double terminated), the equivalent resistance
seen by the LVDS driver is 50 Ω which causes the effective signal swing at the input to be reduced by half. If a
self-terminated receiver requires input swing greater than 250 mVpp (differential) as well as AC coupling to its
inputs, then the LVDS driver with the double-terminated arrangement in Figure 34 may not meet the minimum
input swing requirement; alternatively, the LVPECL or HCSL output driver format with AC coupling is
recommended to meet the minimum input swing required by the self-terminated receiver.
When using AC coupling with LVDS outputs, there may be a startup delay observed in the clock output due to
capacitor charging. The examples in Figure 33 and Figure 34 use 0.1 μF capacitors, but this value may be
adjusted to meet the startup requirements for the particular application.
0.1 PF
CLKoutX
LVDS
Driver
100: Trace
(Differential)
100:
0.1 PF
CLKoutX
K:
Vbias
K:
CLKoutX*
Receiver biasing can be
internal or external through
resistors in K: range
LVDS
Driver
0.1 PF
100:
CLKoutX*
0.1 PF
Source termination for
proper DC bias of the driver
100: Trace
(Differential)
50:
Vbias
50:
Receiver with internal
termination and biasing
through 50: resistors
(b) LVDS DC termination with AC coupling at source and internal termination at load.
Double termination at source and load will reduce swing by half.
(a) LVDS DC termination with AC coupling at load
Figure 33. Differential LVDS Operation with AC Coupling
to Receivers
(a) Without Internal 100-Ω Termination
Figure 34. Differential LVDS Operation with AC Coupling
to Receivers
(b) With Internal 100-Ω Termination
LVPECL drivers require a DC path to ground. When AC coupling an LVPECL signal use 160 Ω emitter resistors
(or 91 Ω for Vcco = 2.5 V) close to the LVPECL driver to provide a DC path to ground as shown in Figure 38. For
proper receiver operation, the signal should be biased to the DC bias level (common mode voltage) specified by
the receiver. The typical DC bias voltage (common mode voltage) for LVPECL receivers is 2 V. Alternatively, a
Thevenin equivalent circuit forms a valid termination as shown in Figure 35 for Vcco = 3.3 V and 2.5 V. Note: this
Thevenin circuit is different from the DC coupled example in Figure 32, since the voltage divider is setting the
input common mode voltage of the receiver.
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RT
RPU
RPD
VBB
3.3V
160:
82:
120:
2V
2.5V
91:
62.5:
250:
2V
Vcco
RPD
Vcco
RPU
RT
Termination and Use of Clock Drivers (continued)
CLKoutX
0.1 PF
LVPECL
Driver
100: Trace
(Differential)
0.1 PF
LVPECL
Reciever
RPD
RT
RPU
CLKoutX*
Vcco
Figure 35. Differential LVPECL Operation, AC Coupling,
Thevenin Equivalent
10.3.3 Termination for Single-Ended Operation
A balun can be used with either LVDS or LVPECL drivers to convert the balanced, differential signal into an
unbalanced, single-ended signal.
It is possible to use an LVPECL driver as one or two separate 800 mV p-p signals. When DC coupling one of the
LMK00308 LVPECL driver of a CLKoutX/CLKoutX* pair, be sure to properly terminate the unused driver. When
DC coupling on of the LMK00308 LVPECL drivers, the termination should be 50 Ω to Vcco - 2 V as shown in
Figure 36. The Thevenin equivalent circuit is also a valid termination as shown in Figure 37 for Vcco = 3.3 V.
50:
Vcco - 2V
CLKoutX
50: Trace
LVPECL
Driver
Vcco - 2V
CLKoutX*
Load
50:
Figure 36. Single-Ended LVPECL Operation, DC Coupling
RPU
Vcco
CLKoutX
Vcco
RPD
50: Trace
CLKoutX*
(unused)
RPD
RPU
LVPECL
Driver
Vcco
RPU
RPD
VTT
3.3V
120:
82:
~1.3V
2.5V
250:
62.5:
0.5V
Load
Figure 37. Single-Ended LVPECL Operation, DC Coupling, Thevenin Equivalent
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Termination and Use of Clock Drivers (continued)
RT
When AC coupling an LVPECL driver use a 160 Ω emitter resistor (or 91 Ω for Vcco = 2.5 V) to provide a DC
path to ground and ensure a 50-Ω termination with the proper DC bias level for the receiver. The typical DC bias
voltage for LVPECL receivers is 2 V. If the companion driver is not used, it should be terminated with either a
proper AC or DC termination. This latter example of AC coupling a single-ended LVPECL signal can be used to
measure single-ended LVPECL performance using a spectrum analyzer or phase noise analyzer. When using
most RF test equipment no DC bias point (0 VDC) is required for safe and proper operation. The internal 50 Ω
termination the test equipment correctly terminates the LVPECL driver being measured as shown in Figure 38.
When using only one LVPECL driver of a CLKoutX/CLKoutX* pair, be sure to properly terminated the unused
driver.
50: Trace
0.1 PF
LVPECL
Driver
RT
CLKoutX*
50:
0.1 PF
Vcco
RT
3.3V
160:
2.5V
91:
50:
CLKoutX
Load
Figure 38. Single-Ended LVPECL Operation, AC Coupling
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11 Power Supply Recommendations
11.1 Power Supply Sequencing
When powering the Vcc and Vcco pins from separate supply rails, it is recommended for the supplies to reach
their regulation point at approximately the same time while ramping up, or reach ground potential at the same
time while ramping down. Using simultaneous or ratiometric power supply sequencing prevents internal current
flow from Vcc to Vcco pins that could occur when Vcc is powered before Vcco.
11.2 Current Consumption and Power Dissipation Calculations
The current consumption values specified in Electrical Characteristics can be used to calculate the total power
dissipation and IC power dissipation for any device configuration. The total VCC core supply current (ICC_TOTAL)
can be calculated using Equation 5:
ICC_TOTAL = ICC_CORE + ICC_BANK_A + ICC_BANK_B + ICC_CMOS
where
•
•
•
•
ICC_CORE is the current for core logic and input blocks and depends on selected input (CLKinX or OSCin).
ICC_BANK_A is the current for Bank A and depends on output type (ICC_PECL, ICC_LVDS, ICC_HCSL, or 0 mA if
disabled).
ICC_BANK_B is the current for Bank B and depends on output type (ICC_PECL, ICC_LVDS, ICC_HCSL, or 0 mA if
disabled).
ICC_CMOS is the current for the LVCMOS output (or 0 mA if REFout is disabled).
(5)
Since the output supplies (VCCOA, VCCOB, VCCOC) can be powered from 3 independent voltages, the respective
output supply currents (ICCO_BANK_A, ICCO_BANK_B, and ICCO_CMOS) should be calculated separately.
ICCO_BANK for either Bank A or B can be directly taken from the corresponding output supply current spec
(ICCO_PECL, ICCO_LVDS, or ICCO_HCSL) provided the output loading matches the specified conditions. Otherwise,
ICCO_BANK should be calculated as follows:
ICCO_BANK = IBANK_BIAS + (N * IOUT_LOAD)
where
•
•
•
IBANK_BIAS is the output bank bias current (fixed value).
IOUT_LOAD is the DC load current per loaded output pair.
N is the number of loaded output pairs per bank (N = 0 to 4).
(6)
Table 6 shows the typical IBANK_BIAS values and IOUT_LOAD expressions for LVPECL, LVDS, and HCSL.
For LVPECL, it is possible to use a larger termination resistor (RT) to ground instead of terminating with 50 Ω to
VTT = Vcco - 2 V; this technique is commonly used to eliminate the extra termination voltage supply (VTT) and
potentially reduce device power dissipation at the expense of lower output swing. For example, when Vcco is 3.3
V, a RT value of 160 Ω to ground will eliminate the 1.3 V termination supply without sacrificing much output
swing. In this case, the typical IOUT_LOAD is 25 mA, so ICCO_PECL for a fully-loaded bank reduces to 126.5 mA (vs.
132 mA with 50 Ω resistors to Vcco - 2 V).
Table 6. Typical Output Bank Bias and Load Currents
CURRENT PARAMETER
LVPECL
LVDS
HCSL
IBANK_BIAS
26.5 mA
26 mA
4.8 mA
IOUT_LOAD
(VOH - VTT)/RT + (VOL - VTT)/RT
0 mA
(No DC load current)
VOH/RT
Once the current consumption is calculated for each supply, the total power dissipation (PTOTAL) can be
calculated as:
PTOTAL = (VCC*ICC_TOTAL) + (VCCOA*ICCO_BANK_A) + (VCCOB*ICCO_BANK_B) + (VCCOC*ICCO_CMOS)
(7)
If the device configuration is configured with LVPECL and/or HCSL outputs, then it is also necessary to calculate
the power dissipated in any termination resistors (PRT_ PECL and PRT_HCSL) and in any LVPECL termination
voltages (PVTT_PECL). The external power dissipation values can be calculated as follows:
PRT_PECL (per LVPECL pair) = (VOH - VTT)2/RT + (VOL - VTT)2/RT
PVTT_PECL (per LVPECL pair) = VTT * [(VOH - VTT)/RT + (VOL - VTT)/RT]
(8)
(9)
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PRT_HCSL (per HCSL pair) = VOH2 / RT
30
(10)
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Finally, the IC power dissipation (PDEVICE) can be computed by subtracting the external power dissipation values
from PTOTAL as follows:
PDEVICE = PTOTAL - N1*(PRT_PECL + PVTT_PECL) - N2*PRT_HCSL
where
•
•
N1 is the number of LVPECL output pairs with termination resistors to VTT (usually Vcco - 2 V or GND).
N2 is the number of HCSL output pairs with termination resistors to GND.
(11)
11.2.1 Power Dissipation Example: Worst-Case Dissipation
This example shows how to calculate IC power dissipation for a configuration to estimate worst-case power
dissipation. In this case, the maximum supply voltage and supply current values specified in Electrical
Characteristics are used.
• VCC = VCCO = 3.465 V. Max ICC and ICCO values.
• CLKin0/CLKin0* input is selected.
• Banks A and B are configured for LVPECL: all outputs terminated with 50 Ω to VT = Vcco - 2 V.
• REFout is enabled with 5 pF load.
• TA = 85 °C
Using the power calculations from the previous section and maximum supply current specifications, we can
compute PTOTAL and PDEVICE.
• From Equation 5: ICC_TOTAL = 10.5 mA + 20 mA + 20 mA + 5.5 mA = 56 mA
• From ICCO_PECL max spec: ICCO_BANK_A = ICCO_BANK_B = 160 mA
• From Equation 7: PTOTAL = 3.465 V * (56 mA + 160 mA + 160 mA + 10 mA) = 1337 mW
• From Equation 8: PRT_PECL = ((2.57 V - 1.47 V)2/50 Ω) + ((1.72 V - 1.47 V)2/50 Ω) = 25.5 mW (per output pair)
• From Equation 9: PVTT_PECL = 1.47 V * [ ((2.57 V - 1.47 V) / 50 Ω) + ((1.72 V - 1.47 V) / 50 Ω) ] = 39.5 mW
(per output pair)
• From Equation 10: PRT_HCSL = 0 mW (no HCSL outputs)
• From Equation 11: PDEVICE = 1337 mW - (8 * (25.5 mW + 39.5 mW)) – 0 mW = 817 mW
In this worst-case example, the IC device will dissipate about 817 mW or 61% of the total power (1337 mW),
while the remaining 39% will be dissipated in the LVPECL emitter resistors (204 mW for 8 pairs) and termination
voltage (316 mW into Vcco - 2 V). Based on θJA of 31.4 °C/W, the estimated die junction temperature would be
about 26 °C above ambient, or 111 °C when TA = 85 °C.
11.3 Power Supply Bypassing
The Vcc and Vcco power supplies should have a high-frequency bypass capacitor, such as 0.1 uF or 0.01 uF,
placed very close to each supply pin. 1 uF to 10 uF decoupling capacitors should also be placed nearby the
device between the supply and ground planes. All bypass and decoupling capacitors should have short
connections to the supply and ground plane through a short trace or via to minimize series inductance.
11.3.1 Power Supply Ripple Rejection
In practical system applications, power supply noise (ripple) can be generated from switching power supplies,
digital ASICs or FPGAs, etc. While power supply bypassing will help filter out some of this noise, it is important to
understand the effect of power supply ripple on the device performance. When a single-tone sinusoidal signal is
applied to the power supply of a clock distribution device, such as LMK00308, it can produce narrow-band phase
modulation as well as amplitude modulation on the clock output (carrier). In the single-side band phase noise
spectrum, the ripple-induced phase modulation appears as a phase spur level relative to the carrier (measured in
dBc).
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Power Supply Bypassing (continued)
For the LMK00308, power supply ripple rejection, or PSRR, was measured as the single-sideband phase spur
level (in dBc) modulated onto the clock output when a ripple signal was injected onto the Vcco supply. The
PSRR test setup is shown in Figure 39.
Ripple
Source
Vcco
Clock
Source
Power
Supplies
Bias-Tee
Vcc
OUT+
IN+
Limiting
Amp
IC
IN-
OUTDUT Board
OUT
Phase Noise
Analyzer
Scope
Measure 100 mVPP
ripple on Vcco at IC
Measure single
sideband phase spur
power in dBc
Figure 39. PSRR Test Setup
A signal generator was used to inject a sinusoidal signal onto the Vcco supply of the DUT board, and the peakto-peak ripple amplitude was measured at the Vcco pins of the device. A limiting amplifier was used to remove
amplitude modulation on the differential output clock and convert it to a single-ended signal for the phase noise
analyzer. The phase spur level measurements were taken for clock frequencies of 156.25 MHz and 312.5 MHz
under the following power supply ripple conditions:
• Ripple amplitude: 100 mVpp on Vcco = 2.5 V
• Ripple frequencies: 100 kHz, 1 MHz, and 10 MHz
Assuming no amplitude modulation effects and small index modulation, the peak-to-peak deterministic jitter (DJ)
can be calculated using the measured single-sideband phase spur level (PSRR) as follows:
DJ (ps pk-pk) = [(2*10(PSRR / 20)) / (π*fCLK)] * 1012
(12)
The “PSRR vs. Ripple Frequency” plots in Typical Characteristics show the ripple-induced phase spur levels for
the differential output types at 156.25 MHz and 312.5 MHz . The LMK00308 exhibits very good and well-behaved
PSRR characteristics across the ripple frequency range for all differential output types. The phase spur levels for
LVPECL are below -64 dBc at 156.25 MHz and below -62 dBc at 312.5 MHz. Using Equation 12, these phase
spur levels translate to Deterministic Jitter values of 2.57 ps pk-pk at 156.25 MHz and 1.62 ps pk-pk at 312.5
MHz. Testing has shown that the PSRR performance of the device improves for Vcco = 3.3 V under the same
ripple amplitude and frequency conditions.
11.4 Thermal Management
Power dissipation in the LMK00308 device can be high enough to require attention to thermal management. For
reliability and performance reasons the die temperature should be limited to a maximum of 125 °C. That is, as an
estimate, TA (ambient temperature) plus device power dissipation times RθJA should not exceed 125 °C.
The package of the device has an exposed pad that provides the primary heat removal path as well as excellent
electrical grounding to the printed circuit board. To maximize the removal of heat from the package a thermal
land pattern including multiple vias to a ground plane must be incorporated on the PCB within the footprint of the
package. The exposed pad must be soldered down to ensure adequate heat conduction out of the package.
32
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Thermal Management (continued)
A recommended land and via pattern is shown in Figure 40. More information on soldering WQFN packages can
be obtained at: http://www.ti.com/packaging.
4.6 mm, min
0.2 mm,
typ
1.2 mm,
typ
Figure 40. Recommended Land and Via Pattern
To minimize junction temperature it is recommended that a simple heat sink be built into the PCB (if the ground
plane layer is not exposed). This is done by including a copper area of about 2 square inches on the opposite
side of the PCB from the device. This copper area may be plated or solder coated to prevent corrosion but
should not have conformal coating (if possible), which could provide thermal insulation. The vias shown in
Figure 40 should connect these top and bottom copper layers and to the ground layer. These vias act as “heat
pipes” to carry the thermal energy away from the device side of the board to where it can be more effectively
dissipated.
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
Common Data Transmission Parameters and their Definitions, Application Note AN-912 (SNLA036)
12.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.3 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
12.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
34
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PACKAGE OPTION ADDENDUM
www.ti.com
6-Mar-2015
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LMK00308SQ/NOPB
ACTIVE
WQFN
RTA
40
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
K00308
LMK00308SQE/NOPB
ACTIVE
WQFN
RTA
40
250
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
K00308
LMK00308SQX/NOPB
ACTIVE
WQFN
RTA
40
2500
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
K00308
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
6-Mar-2015
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
6-Mar-2015
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
LMK00308SQ/NOPB
WQFN
RTA
40
LMK00308SQE/NOPB
WQFN
RTA
LMK00308SQX/NOPB
WQFN
RTA
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
1000
330.0
16.4
6.3
6.3
1.5
12.0
16.0
Q1
40
250
178.0
16.4
6.3
6.3
1.5
12.0
16.0
Q1
40
2500
330.0
16.4
6.3
6.3
1.5
12.0
16.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
6-Mar-2015
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LMK00308SQ/NOPB
WQFN
RTA
40
1000
367.0
367.0
38.0
LMK00308SQE/NOPB
WQFN
RTA
40
250
213.0
191.0
55.0
LMK00308SQX/NOPB
WQFN
RTA
40
2500
367.0
367.0
38.0
Pack Materials-Page 2
PACKAGE OUTLINE
RTA0040A
WQFN - 0.8 mm max height
SCALE 2.200
PLASTIC QUAD FLATPACK - NO LEAD
6.1
5.9
A
B
PIN 1 INDEX AREA
6.1
5.9
0.5
0.3
0.3
0.2
DETAIL
OPTIONAL TERMINAL
TYPICAL
0.8 MAX
C
SEATING PLANE
0.08
0.05
0.00
4.6 0.1
36X 0.5
10
(0.1) TYP
EXPOSED
THERMAL PAD
20
11
21
4X
4.5
SEE TERMINAL
DETAIL
1
PIN 1 ID
(OPTIONAL)
30
40
31
40X
0.5
0.3
40X
0.3
0.2
0.1
0.05
C A
B
4214989/A 12/2014
NOTES:
1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing
per ASME Y14.5M.
2. This drawing is subject to change without notice.
3. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
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EXAMPLE BOARD LAYOUT
RTA0040A
WQFN - 0.8 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
( 4.6)
SYMM
40X (0.25)
31
40
40X (0.6)
1
30
36X (0.5)
(0.74)
TYP
SYMM
(5.8)
(1.48)
TYP
( 0.2) TYP
VIA
10
21
(R0.05) TYP
11
20
(0.74) TYP
(1.48) TYP
(5.8)
LAND PATTERN EXAMPLE
SCALE:12X
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
SOLDER MASK
OPENING
METAL
SOLDER MASK
OPENING
METAL UNDER
SOLDER MASK
NON SOLDER MASK
DEFINED
(PREFERRED)
SOLDER MASK
DEFINED
SOLDER MASK DETAILS
4214989/A 12/2014
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
number SLUA271 (www.ti.com/lit/slua271).
www.ti.com
EXAMPLE STENCIL DESIGN
RTA0040A
WQFN - 0.8 mm max height
PLASTIC QUAD FLATPACK - NO LEAD
(1.48) TYP
9X ( 1.28)
31
40
40X (0.6)
1
30
40X (0.25)
36X (0.5)
(1.48)
TYP
SYMM
(5.8)
METAL
TYP
10
21
(R0.05) TYP
20
11
SYMM
(5.8)
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD
70% PRINTED SOLDER COVERAGE BY AREA
SCALE:15X
4214989/A 12/2014
NOTES: (continued)
5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
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