LMK00334RTVT

LMK00334 SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 LMK00334 Four-Output Clock Buffer and Level Translator for PCIe Gen 1 to Gen 5 1 Features 3 Description • The LMK00334 device is a 4-output HCSL fanout buffer intended for high-frequency, low-jitter clock, data distribution, and level translation. It is capable of distributing the reference clock for ADCs, DACs, multi-gigabit ethernet, XAUI, fibre channel, SATA/SAS, SONET/SDH, CPRI, and high-frequency backplanes. • • • • • • • • 3:1 Input multiplexer – Two universal inputs operate up to 400 MHz 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 two differential outputs each – HCSL, or Hi-Z (selectable) – Additive RMS phase jitter for PCIe Gen5 at 100 MHz: • 15 fs RMS (typical) High PSRR: –72 dBc at 156.25 MHz LVCMOS output with synchronous enable input Pin-controlled configuration VCC core supply: 3.3 V ± 5% Three independent VCCO output supplies: 3.3 V, 2.5 V ± 5% Industrial temperature range: –40°C to +105°C 32-pin WQFN (5 mm × 5 mm) 2 Applications • • • • Data center switches Core routers Servers, computing, PCIe Gen 3.0 to 5.0 Remote radio units and baseband units The input clock can be selected from two universal inputs or one crystal input. The selected input clock is distributed to two banks of two HCSL outputs and one LVCMOS output. The LVCMOS output has a synchronous enable input for runtpulse-free operation when enabled or disabled. The LMK00334 operates from a 3.3-V core supply and three independent 3.3-V or 2.5-V output supplies. The LMK00334 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 LMK00334 (1) PACKAGE WQFN (32) BODY SIZE (NOM) 5.00 mm × 5.00 mm For all available packages, see the orderable addendum at the end of the data sheet. CLKout_EN CLKout_EN LMK00334 Functional Block Diagram 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. LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 Table of Contents 1 Features............................................................................1 2 Applications..................................................................... 1 3 Description.......................................................................1 4 Revision History.............................................................. 2 5 Pin Configuration and Functions...................................3 6 Specifications.................................................................. 4 6.1 Absolute Maximum Ratings........................................ 4 6.2 ESD Ratings............................................................... 4 6.3 Recommended Operating Conditions.........................5 6.4 Thermal Information....................................................5 6.5 Electrical Characteristics.............................................5 6.6 Timing Requirements, Propagation Delay, and Output Skew..................................................................8 6.7 Typical Characteristics................................................ 9 7 Parameter Measurement Information.......................... 11 7.1 Differential Voltage Measurement Terminology.........11 8 Detailed Description......................................................12 8.1 Overview................................................................... 12 8.2 Functional Block Diagram......................................... 12 8.3 Feature Description...................................................12 8.4 Device Functional Modes..........................................14 9 Application and Implementation.................................. 15 9.1 Application Information............................................. 15 9.2 Typical Application.................................................... 15 10 Power Supply Recommendations..............................20 10.1 Current Consumption and Power Dissipation Calculations.................................................................20 10.2 Power Supply Bypassing........................................ 22 11 Layout........................................................................... 23 11.1 Layout Guidelines................................................... 23 11.2 Layout Example...................................................... 23 11.3 Thermal Management............................................. 24 12 Device and Documentation Support..........................25 12.1 Documentation Support.......................................... 25 12.2 Receiving Notification of Documentation Updates..25 12.3 Support Resources................................................. 25 12.4 Trademarks............................................................. 25 12.5 Electrostatic Discharge Caution..............................25 12.6 Glossary..................................................................25 13 Mechanical, Packaging, and Orderable Information.................................................................... 25 4 Revision History Changes from Revision D (July 2021) to Revision E (January 2022) Page • Changed data sheet title.....................................................................................................................................1 • Added links to the Applications section.............................................................................................................. 1 • Added text to the Description section................................................................................................................. 1 • Added example board layout to Packaging Information section.......................................................................25 Changes from Revision C (July 2017) to Revision D (July 2021) Page • Updated the numbering format for tables, figures, and cross-references throughout the document..................1 • Added PCIe Gen 5.0 to the data sheet...............................................................................................................1 • Corrected PN in Figure 9-4 and Figure 9-5 to LMK00334................................................................................ 17 Changes from Revision B (May 2017) to Revision C (July 2017) Page • Added PCIe 4.0 compliance data....................................................................................................................... 5 Changes from Revision A (October 2014) to Revision B (May 2017) Page • Changed CLKout_EN pin to CLKout_EN throughout the data sheet................................................................. 1 • Add pins 28 and 32 to the Pin Functions table .................................................................................................. 3 • Moved the storage temperature to the Absolute Maximum Ratings table.......................................................... 4 • Added test conditions to the output supply voltage parameter in the Recommended Operating Conditions table.................................................................................................................................................................... 5 Changes from Revision * (December 2013) to Revision A (October 2014) Page • Added, updated, or renamed the following sections: Device Information Table, Application and Implementation; Power Supply Recommendations; Layout; Device and Documentation Support; Mechanical, Packaging, and Ordering Information ................................................................................................................ 1 • Changed from 1 MHz to 12 kHz in Electrical Characteristics ............................................................................ 5 • Deleted "The additive jitter The additive RMS jitter was approximated ... "........................................................5 2 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 REFout_EN REFout VCC CLKin1 CLKin1* NC 32 VCCOC VCC 5 Pin Configuration and Functions 31 30 29 28 27 26 25 GND 1 24 GND VCCOA 2 23 VCCOB CLKoutA0 3 22 CLKoutB0 CLKoutA0* 4 21 CLKoutB0* 20 VCCOB 19 CLKoutB1 Top Down View VCCOA 5 CLKoutA1 6 DAP 9 10 11 12 13 14 15 16 CLKin_SEL1 GND CLKin0* 17 CLKin0 8 CLKin_SEL0 GND OSCout CLKoutB1* OSCin 18 VCC 7 CLKout_EN CLKoutA1* Figure 5-1. RTV Package 32-Pin WQFN Top View Table 5-1. Pin Functions(3) PIN I/O DESCRIPTION NAME NO. DAP DAP GND CLKin_SEL0 13 I Clock input selection pins (2) CLKin_SEL1 16 I Clock input selection pins (2) CLKin0 14 I Universal clock input 0 (differential/single-ended) CLKin0* 15 I Universal clock input 0 (differential/single-ended) CLKin1 27 I Universal clock input 1 (differential/single-ended) CLKin1* 26 I Universal clock input 1 (differential/single-ended) CLKout_EN 9 I Bank A and Bank B low active output buffer enable. (2) CLKoutA0 3 O Differential clock output A0. CLKoutA0* 4 O Differential clock output A0. CLKoutA1 6 O Differential clock output A1. CLKoutA1* 7 O Differential clock output A1. CLKoutB1 19 O Differential clock output B1. CLKoutB1* 18 O Differential clock output B1. CLKoutB0 22 O Differential clock output B0. Differential clock output B0. CLKoutB0* GND NC Die Attach Pad. Connect to the PCB ground plane for heat dissipation. 21 O 1, 8 17, 24 GND 25 — Not connected internally. Pin may be floated, grounded, or otherwise tied to any potential within the Supply Voltage range stated in the Absolute Maximum Ratings. Ground OSCin 11 I Input for crystal. Can also be driven by a XO, TCXO, or other external single-ended clock. OSCout 12 O Output for crystal. Leave OSCout floating if OSCin is driven by a single-ended clock. REFout 29 O LVCMOS reference output. Enable output by pulling REFout_EN pin high. REFout_EN 31 I REFout enable input. Enable signal is internally synchronized to selected clock input. (2) Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 3 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 Table 5-1. Pin Functions(3) (continued) PIN I/O DESCRIPTION 10, 28, 32 PWR Power supply for Core and Input Buffer blocks. The VCC supply operates from 3.3 V. Bypass with a 0.1-µF, low-ESR capacitor placed very close to each VCC pin. VCCOA 2, 5 PWR Power supply for Bank A Output buffers. VCCOA operates from 3.3 V or 2.5 V. The VCCOA pins are internally tied together. Bypass with a 0.1-µF, low-ESR capacitor placed very close to each VCCO pin. (1) VCCOB 20, 23 PWR Power supply for Bank B Output buffers. VCCOB operates from 3.3 V or 2.5 V. The VCCOB pins are internally tied together. Bypass with a 0.1-µF, low-ESR capacitor placed very close to each VCCO pin. (1) VCCOC 30 PWR Power supply for REFout buffer. VCCOC operates from 3.3 V or 2.5 V. Bypass with a 0.1-µF, low-ESR capacitor placed very close to each VCCO pin. (1) NAME VCC (1) (2) (3) NO. The output supply voltages or pins (VCCOA, VCCOB, and VCCOC) will be called VCCO in general when no distinction is needed, or when the output supply can be inferred from the output bank/type. CMOS control input with internal pulldown resistor. 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 and Termination and Use of Clock Drivers for output interface and termination techniques. 6 Specifications 6.1 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 TL Lead temperature (solder 4 s) 260 °C TJ Junction temperature 150 °C Tstg Storage temperature 150 °C (1) (2) –65 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. 6.2 ESD Ratings VALUE Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) V(ESD) Electrostatic discharge Charged-device model (CDM), per JEDEC specification JESD22-C101(2) Machine model (MM) (1) (2) 4 UNIT ±2000 ±750 V ±150 JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) TA Ambient temperature TJ Junction temperature VCC Core supply voltage Output supply voltage(1) (2) VCCO (1) (2) MIN TYP –40 25 MAX UNIT 85 °C 125 °C V 3.15 3.3 3.45 3.3-V range 3.3 – 5% 3.3 3.3 + 5% 2.5-V range 2.5 – 5% 2.5 2.5 + 5% V The output supply voltages or pins (VCCOA, VCCOB, and VCCOC) will be called VCCO in general when no distinction is needed, or when the output supply can be inferred from the output bank/type. VCCO for any output bank should be less than or equal to VCC (VCCO ≤ VCC). 6.4 Thermal Information LMK00334(2) THERMAL METRIC(1) RTV (WQFN) UNIT 32 PINS RθJA Junction-to-ambient thermal resistance 38.1 °C/W RθJC(top) Junction-to-case (top) thermal resistance 7.2 °C/W RθJB Junction-to-board thermal resistance 12 °C/W ψJT Junction-to-top characterization parameter 0.4 °C/W ψJB Junction-to-board characterization parameter 11.9 °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance 4.5 °C/W (1) (2) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. Specification assumes 5 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. TI recommends using the maximum number of vias in the board layout. 6.5 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 the 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; because of this, typical values are not ensured. (1) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT CLKinX selected 8.5 10.5 mA OSCin selected 10 13.5 mA ICC_HCSL 50 58.5 mA ICC_CMOS 3.5 5.5 mA 65 81.5 mA VCCO = 3.3 V ±5% 9 10 mA VCCO = 2.5V ± 5% 7 8 mA CURRENT CONSUMPTION (1) ICC_CORE Core supply current, all outputs disabled ICCO_HCSL Additive output supply current, HCSL banks enabled Includes output bank bias and load currents for both banks, RT = 50 Ω on all outputs ICCO_CMOS Additive output supply current, LVCMOS output enabled 200 MHz, CL = 5 pF Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 5 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 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 the 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; because of this, typical values are not ensured. (1) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT POWER SUPPLY RIPPLE REJECTION (PSRR) PSRRHCSL Ripple-induced phase spur level(2) Differential HCSL Output 156.25 MHz –72 312.5 MHz –63 dBc CMOS CONTROL INPUTS (CLKin_SELn, CLKout_TYPEn, REFout_EN) VIH High-level input voltage VIL Low-level input voltage IIH High-level input current VIH = VCC, internal pulldown resistor IIL Low-level input current VIL = 0 V, internal pulldown resistor 1.6 VCC GND 0.4 V 50 μA –5 0.1 V μA CLOCK INPUTS (CLKin0/CLKin0*, CLKin1/CLKin1*) fCLKin Input frequency range(8) VIHD Differential input high voltage VILD Differential input low voltage VID Differential input voltage swing(3) VCMD Differential input CMD commonmode voltage VIH Single-ended input IH high voltage VIL Single-ended input IL low voltage Functional up to 400 MHz Output frequency range and timing specified per output type (refer to LVCMOS output specifications) CLKin driven differentially VCM ISOMUX Mux isolation, CLKin0 to CLKin1 400 MHz Vcc V 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 DCSingle-ended input voltage swing(8) coupled), CLKinX* AC-coupled to GND or externally biased within VCM range Single-ended input CM commonmode voltage VI_SE DC fOFFSET > 50 kHz, 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) External clock frequency range(8) OSCin driven single-ended, OSCout floating FXTAL Crystal frequency range Fundamental mode crystal ESR ≤ 200 Ω (10 to 30 MHz) ESR ≤ 125 Ω (30 to 40 MHz)(4) CIN OSCin input capacitance FCLK 6 10 1 Submit Document Feedback 250 MHz 40 MHz pF Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 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 the 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; because of this, typical values are not ensured. (1) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 400 MHz HCSL OUTPUTS (CLKoutAn/CLKoutAn*, CLKoutBn/CLKoutBn*) fCLKout Output frequency range(8) JitterADD_PCle Additive RMS phase jitter for PCIe 5.0(8) JitterADD_PCle RL = 50 Ω to GND, CL ≤ 5 pF DC PCIe Gen 5 filter CLKin: 100 MHz, slew rate ≥ 0.5 V/ns 0.015 0.03 ps Additive RMS phase jitter for PCIe 4.0(8) PCIe Gen 4, PLL BW = 2–5 MHz, CDR = 10 MHz CLKin: 100 MHz, slew rate ≥ 1.8 V/ns 0.03 0.05 ps JitterADD_PCle Additive RMS phase jitter for PCIe 3.0(8) PCIe Gen 3, PLL BW = 2–5 MHz, CDR = 10 MHz CLKin: 100 MHz, slew rate ≥ 0.6 V/ns 0.03 0.15 ps JitterADD Additive RMS jitter integration bandwidth 12 MHz to 20 MHz(5) VCCO = 3.3 V, RT = 50 Ω to GND CLKin: 100 MHz, slew rate ≥ 3 V/ns 77 Noise Floor Noise floor fOFFSET ≥ 10 MHz(6) (7) VCCO = 3.3 V, RT = 50 Ω to GND CLKin: 100 MHz, slew rate ≥ 3 V/ns –161.3 DUTY Duty cycle(8) 50% input clock duty cycle 45% VOH Output high voltage 810 920 mV Output low voltage TA = 25°C, DC measurement, RT = 50 Ω to GND 520 VOL –150 0.5 150 mV 250 350 460 mV 140 mV 225 400 ps 225 400 ps 250 MHz voltage(8) (9) VCROSS Absolute crossing ΔVCROSS Total variation of VCROSS (8) (9) tR Output rise time 20% to tF Output fall time 80% to 80%(9) (12) 20%(9) (12) RL = 50 Ω to GND, CL ≤ 5 pF 250 MHz, uniform transmission line up to 10 in. with 50-Ω characteristic impedance, RL = 50 Ω to GND, CL ≤ 5 pF fs dBc/Hz 55% LVCMOS OUTPUT (REFout) fCLKout Output frequency range(8) CL ≤ 5 pF JitterADD Additive RMS jitter integration bandwidth 1 MHz to 20 MHz(5) VCCO = 3.3 V, CL ≤ 5 pF 100 MHz, input slew rate ≥ 3 V/ns 95 Noise Floor Noise floor fOFFSET ≥ 10 MHz(6) (7) VCCO = 3.3 V, CL ≤ 5 pF 100 MHz, input slew rate ≥ 3 V/ns –159.3 DUTY Duty cycle(8) 50% input clock duty cycle VOH Output high voltage VOL Output low voltage IOH Output high current (source) IOL Output rise time 20% to 80%(9) (12) tF 20%(10) (12) time(10) Output enable tDIS Output disable time(10) (1) (2) (3) dBc/Hz 55% V 0.1 tR tEN 45% fs VCCO – 0.1 1-mA load Output low current (sink) Output fall time 80% to DC VO = VCCO / 2 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 in. 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 See Power Supply Recommendations and Thermal Management 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 See Differential Voltage Measurement Terminology for definition of VID and VOD voltages. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 7 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 (4) The ESR requirements stated must be met to ensure that the oscillator circuitry has no start-up 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. (5) For the 100-MHz and 156.25-MHz clock input conditions, Additive RMS Jitter (JADD) is calculated using Method #1: JADD = SQRT(JOUT 2 - JSOURCE 2), 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 12-kHz to 20-MHz bandwidth. The phase noise power can be calculated as: dBc = Noise Floor + 10 × log10(20 MHz – 12 kHz). (6) 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. (7) 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, TI recommends using the highest possible input slew rate for differential clocks to achieve optimal noise floor performance at the device outputs. (8) Specification is ensured by characterization and is not tested in production. (9) AC timing parameters for HCSL or CMOS are dependent on output capacitive loading. (10) 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. (11) 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. (12) Parameter is specified by design, not tested in production. 6.6 Timing Requirements, Propagation Delay, and Output Skew MIN tPD_HCSL Propagation delay CLKin-to-HCSL tPD_CMOS Propagation delay CLKin-to-LVCMOS(1) (2) Output skew(11) (9) (4) tSK(O) tSK(PP) (1) (2) (3) (4) 8 (1) (2) Part-to-part output skew(1) (2) (3) RT = 50 Ω to GND, CL ≤ 5 pF CL ≤ 5 pF TYP MAX UNIT ps 295 590 885 VCCO = 3.3 V 900 1475 2300 VCCO = 2.5 V 1000 1550 2700 30 50 ps 80 120 ps Skew specified between any two CLKouts. Load conditions are the same as propagation delay specifications. ps AC timing parameters for HCSL or CMOS are dependent on output capacitive loading. Parameter is specified by design, not tested in production. 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. Specification is ensured by characterization and is not tested in production. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 6.7 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. 1.00 1.0 OUTPUT SWING (V) OUTPUT SWING (V) 0.8 0.6 0.4 0.2 0.0 0.50 0.25 0.00 -0.25 -0.50 -1.00 0 1 2 3 TIME (ns) 4 5 Figure 6-1. HCSL Output Swing at 250 MHz -140 0 1 2 3 4 TIME (ns) 5 6 Figure 6-2. LVCMOS Output Swing at 250 MHz -135 HCSL LVCMOS CLKin Source HCSL CLKin Source -140 Noise Floor (dBc/Hz) -145 Noise Floor (dBc/Hz) load load -0.75 -0.2 -150 -155 -160 -165 -145 -150 -155 -160 -170 -165 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Differential Input Slew Rate (V/ns) Fclk = 100 MHz Foffset = 20 MHz 400 350 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Differential Input Slew Rate (V/ns) Fclk = 156.25 MHz Figure 6-3. Noise Floor vs. CLKin Slew Rate at 100 MHz Foffset = 20 MHz Figure 6-4. Noise Floor vs. CLKin Slew Rate at 156.25 MHz 500 HCSL LVCMOS CLKin Source 450 HCSL CLKin Source 400 RMS Jitter (fs) 300 RMS Jitter (fs) Vcco=3.3 V, AC coupled, 50 Vcco=2.5 V, AC coupled, 50 0.75 250 200 150 350 300 250 200 150 100 100 50 50 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Differential Input Slew Rate (V/ns) Fclk = 100 MHz Int. BW = 1 to 20 MHz Figure 6-5. RMS Jitter vs. CLKin Slew Rate at 100 MHz 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Differential Input Slew Rate (V/ns) Fclk = 156.25 MHz Int. BW = 1 to 20 MHz Figure 6-6. RMS Jitter vs. CLKin Slew Rate at 156.25 MHz Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 9 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 6.7 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. -50 HCSL Ripple Induced Spur Level (dBc) Ripple Induced Spur Level (dBc) -50 -55 -60 -65 -70 -75 -80 -85 1 Ripple Frequency (MHz) Fclk = 156.25 MHz Vccco Ripple = 100 mVpp 1950 HCSL (0.35 ps/°C) LVCMOS (2.2 ps/°C) 1850 750 Right Y-axis plot 1750 550 1650 450 1550 350 1450 250 1350 -25 0 25 50 75 Temperature (°C) REFout Propagation Delay (ps) CLKout Propagation Delay (ps) -70 -75 -80 -85 .1 Figure 6-7. PSRR vs. Ripple Frequency at 156.25 MHz -50 -65 10 Fclk = 312.5 MHz 200 10 Vccco Ripple = 100 mVpp 20 MHz Crystal 40 MHz Crystal 175 150 125 100 75 50 25 0 0 100 Figure 6-9. Propagation Delay vs. Temperature 1 Ripple Frequency (MHz) Figure 6-8. PSRR vs. Ripple Frequency at 312.5 MHz CRYSTAL POWER DISSIPATION ( W) .1 650 -60 -90 -90 850 HCSL -55 500 1k 1.5k 2k 2.5k 3k 3.5k 4k RLIM( ) Figure 6-10. Crystal Power Dissipation vs. RLIM Figure 6-11. HCSL Phase Noise at 100 MHz 10 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 7 Parameter Measurement Information 7.1 Differential Voltage Measurement Terminology The differential voltage of a differential signal can be described by two different definitions, causing confusion when reading data sheets 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 noninverting 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 noninverting 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 7-1 illustrates the two different definitions side-by-side for inputs and Figure 7-2 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 noninverting 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 noninverting signal voltage potential is now increasing and decreasing above and below the noninverting reference. Thus the peak-to-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 VID = | VIH ± VIL | VSS = 2· VID GND Figure 7-1. 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 7-2. Two Different Definitions for Differential Output Signals Refer to Common Data Transmission Parameters and their Definitions (SNLA036) for more information. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 11 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 8 Detailed Description 8.1 Overview The LMK00334 is a 4-output HCSL clock fanout buffer with low additive jitter that can operate up to 400 MHz. It features a 3:1 input multiplexer with an optional crystal oscillator input, two banks of two HCSL outputs, one LVCMOS output, and three independent output buffer supplies. The input selection and output buffer modes are controlled through pin strapping. The device is offered in a 32-pin WQFN package and leverages much of the high-speed, low-noise circuit design employed in the LMK04800 family of clock conditioners. 8.2 Functional Block Diagram CLKout_EN CLKout_EN 8.3 Feature Description 8.3.1 Crystal Power Dissipation vs. RLIM For Figure 6-10, the following applies: • 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(JOUT 2 – JSOURCE 2). • 20-MHz crystal characteristics: Abracon ABL series, AT cut, CL = 18 pF, C0 = 4.4 pF measured (7 pF maximum), ESR = 8.5 Ω measured (40 Ω maximum), and Drive Level = 1 mW maximum (100 µW typical). • 40-MHz crystal characteristics: Abracon ABLS2 series, AT cut, CL = 18 pF, C0 = 5 pF measured (7 pF maximum), ESR = 5 Ω measured (40 Ω maximum), and Drive Level = 1 mW maximum (100 µW typical). 12 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 8.3.2 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 8-1. 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 driven by a single-ended clock (up to 250 MHz) instead of a crystal. Table 8-1. Input Selection CLKin_SEL1 CLKin_SEL0 SELECTED INPUT 0 0 CLKin0, CLKin0* 0 1 CLKin1, CLKin1* 1 X OSCin Table 8-2 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 8-2. CLKin Input vs. Output States 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 8.3.3 Clock Outputs The HCSL output buffer for both Bank A and B outputs are can be disabled to Hi-Z using the CLKout_EN [1:0] as shown in Table 8-3. 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 all differential outputs are not used, TI recommends disabling (Hi-Z) the banks 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 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 8-3. Differential Output Buffer Type Selection CLKout_EN CLKoutX BUFFER TYPE (BANK A AND B) 0 HCSL 1 Disabled (Hi-Z) Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 13 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 8.3.3.1 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 8-4. Table 8-4. 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 three cycles (tEN) of the input clock after REFout_EN is toggled high. REFout will be disabled within three 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. 8.4 Device Functional Modes 8.4.1 VCC and VCCO Power Supplies The LMK00334 has separate 3.3-V core supplies (VCC) and three independent 3.3-V or 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 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 Take care to ensure the VCCO voltages do not exceed the VCC voltage to prevent turning-on the internal ESD protection circuitry. 14 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 9 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, as well as validating and testing their design implementation to confirm system functionality. 9.1 Application Information A common PCIe application, such as a server card, consists of several building blocks, which all need a reference clock. In the mostly used Common RefClk architecture, the clock is distributed from a single source to both RX and TX. This requires either a Clock generator with high output count or a buffer like the LMK00334. The buffer simplifies the clocking tree and provides a cost and space optimized solution. While using a buffer to distribute the clock, the additive jitter must be considered. The LMK00334 is an ultra-low additive jitter PCIe clock buffer suitable for all current and future PCIe Generations. 9.2 Typical Application Mainboard MAC 100 MHz Reference Oscillator PCI Express® PHY (e.g.: XIO1100) Fan Out Buffer (e.g.: LMK0022) PCI Express® Fan-out Switch (e.g.: XIO3130) Connector PCI Express® Device FPGA with PCI Express® Core Add-In Card Data Clock Figure 9-1. Example PCI Express Application Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 15 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 9.2.1 Design Requirements 9.2.1.1 Driving the Clock Inputs The LMK00334 has two universal inputs (CLKin0/CLKin0* and CLKin1/CLKin1*) that can accept DC-coupled, 3.3-V or 2.5-V LVPECL, LVDS, CML, SSTL, and other differential and single-ended signals that meet the input requirements specified in 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 TI recommends driving 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 3.3-V or 2.5-V 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 9-2. 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 9-2. Single-Ended LVCMOS Input, AC Coupling A single-ended clock may also be DC-coupled to CLKinX as shown in Figure 9-3. A 50-Ω load resistor should be placed near the CLKin 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. 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 9-3. Single-Ended LVCMOS Input, DC Coupling With Common-Mode Biasing 16 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 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 9-4. 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, TI recommends using either universal input (CLKinX) because 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 OSCin 50: 50: Trace OSCout LMK00334 RS 0.1 PF CMOS Driver Figure 9-4. Driving OSCin With a Single-Ended Input 9.2.1.2 Crystal Interface The LMK00334 has an integrated crystal oscillator circuit that supports a fundamental mode, AT-cut crystal. The crystal interface is shown in Figure 9-5. C1 XTAL RLIM OSCout LMK00334 OSCin C2 Figure 9-5. Crystal Interface The load capacitance (CL) is specific to the crystal, but usually on the order of 18 to 20 pF. While CL is specified for the crystal, the OSCin input capacitance (CIN = 1 pF typical) of the device and PCB stray capacitance (CSTRAY is approximately around 1 to 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 = C1 2 / (2 × C1) + CIN + CSTRAY (2) Finally, solve for C1: C1 = (CL – CIN – CSTRAY) × 2 (3) 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 must ensure the crystal power dissipation Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 17 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 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 = IRMS 2 × RESR × (1 + C0/CL)2 (4) where • • • • IRMS is the RMS current through the crystal. RESR is the maximum equivalent series resistance specified for the crystal CL is the load capacitance specified for the crystal C0 is the minimum shunt capacitance specified for the crystal IRMS can be measured using a current probe (Tektronix CT-6 or equivalent, for example) placed on the leg of the crystal connected to OSCout with the oscillation circuit active. As shown in Figure 9-5, 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. 9.2.2 Detailed Design Procedure 9.2.2.1 Termination and Use of Clock Drivers When terminating clock drivers, keep these guidelines in mind 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. – HCSL drivers are switched current outputs and require a DC path to ground through 50-Ω termination. 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. 9.2.2.2 Termination for DC-Coupled Differential Operation 50: For DC-coupled operation of an HCSL driver, terminate with 50 Ω to ground near the driver output as shown in Figure 9-6. 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. CLKoutX Rs HCSL Driver 50: Traces Rs HCSL Receiver 50: CLKoutX* Figure 9-6. HCSL Operation, DC Coupling 18 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 9.2.2.3 Termination for AC-Coupled Differential Operation AC coupling allows for shifting the DC bias level (common-mode voltage) when driving different receiver standards. Because 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. 9.2.3 Application Curve Figure 9-7. HCSL Phase Noise at 100 MHz Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 19 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 10 Power Supply Recommendations 10.1 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_BANKS + ICC_CMOS (5) where • • • ICC_CORE is the VCC current for core logic and input blocks and depends on selected input (CLKinX or OSCin). ICC_HCSL is the VCC current for Banks A and B ICC_CMOS is the VCC current for the LVCMOS output (or 0 mA if REFout is disabled). Because the output supplies (VCCOA, VCCOB, VCCOC) can be powered from three 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 may be taken as 50% of the corresponding output supply current specified for two banks (ICCO_HCSL) provided the output loading matches the specified conditions. Otherwise, ICCO_BANK should be calculated per bank as shown in Equation 6: ICCO_BANK = IBANK_BIAS + (N × IOUT_LOAD) (6) 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 (N = 0 to 2). Table 10-1 shows the typical IBANK_BIAS values and IOUT_LOAD expressions for HCSL. Table 10-1. Typical Output Bank Bias and Load Currents CURRENT PARAMETER HCSL IBANK_BIAS 2.4 mA IOUT_LOAD VOH/RT Once the current consumption is known for each supply, the total power dissipation (PTOTAL) can be calculated by Equation 7: PTOTAL = (VCC × ICC_TOTAL) + (VCCOA × ICCO_BANK) + (VCCOB × ICCO_BANK) + (VCCOC × ICCO_CMOS) (7) If the device is configured with HCSL outputs, then it is also necessary to calculate the power dissipated in any termination resistors (PRT_HCSL). The external power dissipation values can be calculated by Equation 8: PRT_HCSL (per HCSL pair) = VOH 2 / RT (8) Finally, the IC power dissipation (PDEVICE) can be computed by subtracting the external power dissipation values from PTOTAL as shown in Equation 9: PDEVICE = PTOTAL – N × PRT_HCSL (9) where • 20 N is the number of HCSL output pairs with termination resistors to GND. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 10.1.1 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: • • • • • Max VCC = VCCO = 3.465 V. Max ICC and ICCO values. CLKin0/CLKin0* input is selected. Banks A and B are enabled, and all outputs are terminated with 50 Ω to GND. REFout is enabled with 5-pF load. TA =85°C Using the power calculations from the previous section and maximum supply current specifications, the user can compute PTOTAL and PDEVICE. • • • • • From Equation 5: ICC_TOTAL = 10.5 mA + 58.5 mA + 5.5 mA = 74.5 mA From ICCO_HCSL max spec: ICCO_BANK = 50% of ICCO_HCSL = 40.75 mA From Equation 7: PTOTAL = (3.465 V × 74.5 mA) + (3.465 V × 40.75 mA) + (3.465 V × 40.75 mA) + (3.465 V × 10 mA) = 575.2 mW From Equation 8: PRT_HCSL = (0.92 V)2 / 50 Ω = 16.9 mW (per output pair) From Equation 9: PDEVICE = 575.2 mW – (4 × 16.9 mW) = 510.4 mW In this worst-case example, the IC device will dissipate about 510.4 mW or 88.7% of the total power (575.2 mW), while the remaining 11.3% will be dissipated in the termination resistors (64.8 mW for 4 pairs). Based on RθJA of 38.1°C/W, the estimate die junction temperature would be about 19.4°C above ambient, or 104.4°C when TA = 85°C. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 21 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 10.2 Power Supply Bypassing The VCC and VCCO power supplies should have a high-frequency bypass capacitor, such as 0.1 µF or 0.01 µF, placed very close to each supply pin. 1-µF to 10-µF 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. 10.2.1 Power Supply Ripple Rejection In practical system applications, power supply noise (ripple) can be generated from switching power supplies, digital ASICs or FPGAs, and so forth. 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 LMK00334, 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). For the LMK00334, 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 10-1. Ripple Source Vcco Clock Source Power Supplies Bias-Tee Vcc OUT+ IN+ Limiting Amp IC IN- DUT Board OUT- OUT Phase Noise Analyzer Scope Measure 100 mVPP ripple on Vcco at IC Measure single sideband phase spur power in dBc Figure 10-1. PSRR Test Setup A signal generator was used to inject a sinusoidal signal onto the VCCO supply of the DUT board, and the peak-to-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 (10) The PSRR vs. Ripple Frequency plots in Typical Characteristics show the ripple-induced phase spur levels at 156.25 MHz and 312.5 MHz. The LMK00334 exhibits very good and well-behaved PSRR characteristics across the ripple frequency range. The phase spur levels for HCSL are below –72 dBc at 156.25 MHz and below –63 dBc at 312.5 MHz. Using Equation 10, these phase spur levels translate to Deterministic Jitter values of 1.02 ps pk-pk at 156.25 MHz and 1.44 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. 22 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 11 Layout 11.1 Layout Guidelines For this device, consider the following guidelines: • • • • • For DC-coupled operation of an HCSL driver, terminate with 50 Ω to ground near the driver output as shown in Figure 11-1. Keep the connections between the bypass capacitors and the power supply on the device as short as possible. Ground the other side of the capacitor using a low impedance connection to the ground plane. If the capacitors are mounted on the back side, 0402 components can be employed. However, soldering to the Thermal Dissipation Pad can be difficult. For component side mounting, use 0201 body size capacitors to facilitate signal routing. 11.2 Layout Example Figure 11-1. LMK00334 Layout Example Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 23 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 11.3 Thermal Management Power dissipation in the LMK00334 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. A recommended land and via pattern is shown in Figure 11-2. More information on soldering WQFN packages can be obtained at: https://www.ti.com/packaging. 3.1 mm, min 0.2 mm, typ 1.27 mm, typ Figure 11-2. Recommended Land and Via Pattern To minimize junction temperature, TI recommends building a simple heat sink 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 11-2 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. 24 Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 LMK00334 www.ti.com SNAS635E – DECEMBER 2013 – REVISED JANUARY 2022 12 Device and Documentation Support 12.1 Documentation Support 12.1.1 Related Documentation For related documents, see the following: • • • • • Absolute Maximum Ratings for Soldering (SNOA549) Common Data Transmission Parameters and their Definitions (SNLA036) "How to Optimize Clock Distribution in PCIe Applications" on the Texas Instruments E2E community forum LMK00338EVM User's Guide (SNAU155) Semiconductor and IC Package Thermal Metrics (SPRA953). 12.2 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. Click on Subscribe to updates to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 12.3 Support Resources TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight from the experts. Search existing answers or ask your own question to get the quick design help you need. Linked content is 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. 12.4 Trademarks TI E2E™ is a trademark of Texas Instruments. All trademarks are the property of their respective owners. 12.5 Electrostatic Discharge Caution This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. 12.6 Glossary 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. Submit Document Feedback Copyright © 2022 Texas Instruments Incorporated Product Folder Links: LMK00334 25 PACKAGE OPTION ADDENDUM www.ti.com 12-Nov-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LMK00334RTVR ACTIVE WQFN RTV 32 1000 RoHS & Green SN Level-3-260C-168 HR -40 to 85 K00334 LMK00334RTVT ACTIVE WQFN RTV 32 250 RoHS & Green SN Level-3-260C-168 HR -40 to 85 K00334 (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) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of