SNAS605AS March   2013  – May 2020 LMK04821 , LMK04826 , LMK04828

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison Table
    1. 5.1 Device Configuration Information
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 SPI Interface Timing
    7. 7.7 Typical Characteristics – Clock Output AC Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Charge Pump Current Specification Definitions
      1. 8.1.1 Charge Pump Output Current Magnitude Variation Vs. Charge Pump Output Voltage
      2. 8.1.2 Charge Pump Sink Current Vs. Charge Pump Output Source Current Mismatch
      3. 8.1.3 Charge Pump Output Current Magnitude Variation Vs. Ambient Temperature
    2. 8.2 Differential Voltage Measurement Terminology
  9. 9 Detailed Description
    1. 9.1 Overview
      1. 9.1.1  Jitter Cleaning
      2. 9.1.2  JEDEC JESD204B Support
      3. 9.1.3  Three PLL1 Redundant Reference Inputs
      4. 9.1.4  VCXO/Crystal Buffered Output
      5. 9.1.5  Frequency Holdover
      6. 9.1.6  PLL2 Integrated Loop Filter Poles
      7. 9.1.7  Internal VCOs
        1. 9.1.7.1 VCO1 Divider (LMK04821 only)
      8. 9.1.8  External VCO Mode
      9. 9.1.9  Clock Distribution
        1. 9.1.9.1 Device Clock Divider
        2. 9.1.9.2 SYSREF Clock Divider
        3. 9.1.9.3 Device Clock Delay
        4. 9.1.9.4 SYSREF Delay
        5. 9.1.9.5 Glitchless Half Step and Glitchless Analog Delay
        6. 9.1.9.6 Programmable Output Formats
        7. 9.1.9.7 Clock Output Synchronization
      10. 9.1.10 Zero-Delay
      11. 9.1.11 Status Pins
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 SYNC/SYSREF
      2. 9.3.2 JEDEC JESD204B
        1. 9.3.2.1 How To Enable SYSREF
          1. 9.3.2.1.1 Setup of SYSREF Example
          2. 9.3.2.1.2 SYSREF_CLR
        2. 9.3.2.2 SYSREF Modes
          1. 9.3.2.2.1 SYSREF Pulser
          2. 9.3.2.2.2 Continuous SYSREF
          3. 9.3.2.2.3 SYSREF Request
      3. 9.3.3 Digital Delay
        1. 9.3.3.1 Fixed Digital Delay
          1. 9.3.3.1.1 Fixed Digital Delay Example
        2. 9.3.3.2 Dynamic Digital Delay
        3. 9.3.3.3 Single and Multiple Dynamic Digital Delay Example
      4. 9.3.4 SYSREF to Device Clock Alignment
      5. 9.3.5 Input Clock Switching
        1. 9.3.5.1 Input Clock Switching - Manual Mode
        2. 9.3.5.2 Input Clock Switching - Pin Select Mode
        3. 9.3.5.3 Input Clock Switching - Automatic Mode
      6. 9.3.6 Digital Lock Detect
      7. 9.3.7 Holdover
        1. 9.3.7.1 Enable Holdover
          1. 9.3.7.1.1 Fixed (Manual) CPout1 Holdover Mode
          2. 9.3.7.1.2 Tracked CPout1 Holdover Mode
        2. 9.3.7.2 Entering Holdover
        3. 9.3.7.3 During Holdover
        4. 9.3.7.4 Exiting Holdover
        5. 9.3.7.5 Holdover Frequency Accuracy and DAC Performance
        6. 9.3.7.6 Holdover Mode - Automatic Exit of Holdover
    4. 9.4 Device Functional Modes
      1. 9.4.1 Dual PLL
      2. 9.4.2 Zero-Delay Dual PLL
      3. 9.4.3 Single-Loop Mode
      4. 9.4.4 Single-Loop Mode With External VCO
      5. 9.4.5 Distribution Mode
    5. 9.5 Programming
      1. 9.5.1 Recommended Programming Sequence
        1. 9.5.1.1 SPI LOCK
        2. 9.5.1.2 SYSREF_CLR
        3. 9.5.1.3 RESET Pin
    6. 9.6 Register Maps
      1. 9.6.1 Register Map for Device Programming
    7. 9.7 Device Register Descriptions
      1. 9.7.1 System Functions
        1. 9.7.1.1 RESET, SPI_3WIRE_DIS
        2. 9.7.1.2 POWERDOWN
        3. 9.7.1.3 ID_DEVICE_TYPE
        4. 9.7.1.4 ID_PROD[15:8], ID_PROD
        5. 9.7.1.5 ID_MASKREV
        6. 9.7.1.6 ID_VNDR[15:8], ID_VNDR
      2. 9.7.2 (0x100 - 0x138) Device Clock and SYSREF Clock Output Controls
        1. 9.7.2.1 CLKoutX_Y_ODL, CLKoutX_Y_IDL, DCLKoutX_DIV
        2. 9.7.2.2 DCLKoutX_DDLY_CNTH, DCLKoutX_DDLY_CNTL
        3. 9.7.2.3 DCLKoutX_ADLY, DCLKoutX_ADLY_MUX, DCLKout_MUX
        4. 9.7.2.4 DCLKoutX_HS, SDCLKoutY_MUX, SDCLKoutY_DDLY, SDCLKoutY_HS
        5. 9.7.2.5 SDCLKoutY_ADLY_EN, SDCLKoutY_ADLY
        6. 9.7.2.6 DCLKoutX_DDLY_PD, DCLKoutX_HSg_PD, DCLKout_ADLYg_PD, DCLKout_ADLY_PD, DCLKoutX_Y_PD, SDCLKoutY_DIS_MODE, SDCLKoutY_PD
        7. 9.7.2.7 SDCLKoutY_POL, SDCLKoutY_FMT, DCLKoutX_POL, DCLKoutX_FMT
      3. 9.7.3 SYSREF, SYNC, and Device Config
        1. 9.7.3.1  VCO_MUX, OSCout_MUX, OSCout_FMT
        2. 9.7.3.2  SYSREF_CLKin0_MUX, SYSREF_MUX
        3. 9.7.3.3  SYSREF_DIV[12:8], SYSREF_DIV[7:0]
        4. 9.7.3.4  SYSREF_DDLY[12:8], SYSREF_DDLY[7:0]
        5. 9.7.3.5  SYSREF_PULSE_CNT
        6. 9.7.3.6  PLL2_NCLK_MUX, PLL1_NCLK_MUX, FB_MUX, FB_MUX_EN
        7. 9.7.3.7  PLL1_PD, VCO_LDO_PD, VCO_PD, OSCin_PD, SYSREF_GBL_PD, SYSREF_PD, SYSREF_DDLY_PD, SYSREF_PLSR_PD
        8. 9.7.3.8  DDLYdSYSREF_EN, DDLYdX_EN
        9. 9.7.3.9  DDLYd_STEP_CNT
        10. 9.7.3.10 SYSREF_CLR, SYNC_1SHOT_EN, SYNC_POL, SYNC_EN, SYNC_PLL2_DLD, SYNC_PLL1_DLD, SYNC_MODE
        11. 9.7.3.11 SYNC_DISSYSREF, SYNC_DISX
        12. 9.7.3.12 Fixed Registers (0x145, 0x171 - 0x172)
      4. 9.7.4 (0x146 - 0x149) CLKin Control
        1. 9.7.4.1 CLKin2_EN, CLKin1_EN, CLKin0_EN, CLKin2_TYPE, CLKin1_TYPE, CLKin0_TYPE
        2. 9.7.4.2 CLKin_SEL_POL, CLKin_SEL_MODE, CLKin1_OUT_MUX, CLKin0_OUT_MUX
        3. 9.7.4.3 CLKin_SEL0_MUX, CLKin_SEL0_TYPE
        4. 9.7.4.4 SDIO_RDBK_TYPE, CLKin_SEL1_MUX, CLKin_SEL1_TYPE
      5. 9.7.5 RESET_MUX, RESET_TYPE
      6. 9.7.6 (0x14B - 0x152) Holdover
        1. 9.7.6.1 LOS_TIMEOUT, LOS_EN, TRACK_EN, HOLDOVER_FORCE, MAN_DAC_EN, MAN_DAC[9:8]
        2. 9.7.6.2 MAN_DAC[9:8], MAN_DAC[7:0]
        3. 9.7.6.3 DAC_TRIP_LOW
        4. 9.7.6.4 DAC_CLK_MULT, DAC_TRIP_HIGH
        5. 9.7.6.5 DAC_CLK_CNTR
        6. 9.7.6.6 CLKin_OVERRIDE, HOLDOVER_PLL1_DET, HOLDOVER_LOS_DET, HOLDOVER_VTUNE_DET, HOLDOVER_HITLESS_SWITCH, HOLDOVER_EN
        7. 9.7.6.7 HOLDOVER_DLD_CNT[13:8], HOLDOVER_DLD_CNT[7:0]
      7. 9.7.7 (0x153 - 0x15F) PLL1 Configuration
        1. 9.7.7.1 CLKin0_R[13:8], CLKin0_R[7:0]
        2. 9.7.7.2 CLKin1_R[13:8], CLKin1_R[7:0]
        3. 9.7.7.3 CLKin2_R[13:8], CLKin2_R[7:0]
        4. 9.7.7.4 PLL1_N
        5. 9.7.7.5 PLL1_WND_SIZE, PLL1_CP_TRI, PLL1_CP_POL, PLL1_CP_GAIN
        6. 9.7.7.6 PLL1_DLD_CNT[13:8], PLL1_DLD_CNT[7:0]
        7. 9.7.7.7 PLL1_R_DLY, PLL1_N_DLY
        8. 9.7.7.8 PLL1_LD_MUX, PLL1_LD_TYPE
      8. 9.7.8 (0x160 - 0x16E) PLL2 Configuration
        1. 9.7.8.1 PLL2_R[11:8], PLL2_R[7:0]
        2. 9.7.8.2 PLL2_P, OSCin_FREQ, PLL2_XTAL_EN, PLL2_REF_2X_EN
        3. 9.7.8.3 PLL2_N_CAL
        4. 9.7.8.4 PLL2_FCAL_DIS, PLL2_N
        5. 9.7.8.5 PLL2_WND_SIZE, PLL2_CP_GAIN, PLL2_CP_POL, PLL2_CP_TRI
        6. 9.7.8.6 SYSREF_REQ_EN, PLL2_DLD_CNT
        7. 9.7.8.7 PLL2_LF_R4, PLL2_LF_R3
        8. 9.7.8.8 PLL2_LF_C4, PLL2_LF_C3
        9. 9.7.8.9 PLL2_LD_MUX, PLL2_LD_TYPE
      9. 9.7.9 (0x16F - 0x1FFF) Misc Registers
        1. 9.7.9.1  PLL2_PRE_PD, PLL2_PD
        2. 9.7.9.2  VCO1_DIV
        3. 9.7.9.3  OPT_REG_1
        4. 9.7.9.4  OPT_REG_2
        5. 9.7.9.5  RB_PLL1_LD_LOST, RB_PLL1_LD, CLR_PLL1_LD_LOST
        6. 9.7.9.6  RB_PLL2_LD_LOST, RB_PLL2_LD, CLR_PLL2_LD_LOST
        7. 9.7.9.7  RB_DAC_VALUE(MSB), RB_CLKinX_SEL, RB_CLKinX_LOS
        8. 9.7.9.8  RB_DAC_VALUE
        9. 9.7.9.9  RB_HOLDOVER
        10. 9.7.9.10 SPI_LOCK
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Digital Lock Detect Frequency Accuracy
      1. 10.2.1 Minimum Lock Time Calculation Example
    3. 10.3 Driving CLKin and OSCin Inputs
      1. 10.3.1 Driving CLKin and OSCin Pins With a Differential Source
      2. 10.3.2 Driving CLKin and OSCin Pins With a Single-Ended Source
    4. 10.4 Output Termination and Biasing
      1. 10.4.1 LVPECL
      2. 10.4.2 LVDS/HSDS
    5. 10.5 Typical Applications
      1. 10.5.1 Design Example
        1. 10.5.1.1 Design Requirements
        2. 10.5.1.2 Detailed Design Procedure
          1. 10.5.1.2.1 Device Configuration and Simulation - PLLatinum Sim
          2. 10.5.1.2.2 Device Programming
        3. 10.5.1.3 Application Curves
    6. 10.6 System Examples
      1. 10.6.1 System Level Diagram
    7. 10.7 Do's and Don'ts
  11. 11Power Supply Recommendations
    1. 11.1 Pin Connection Recommendations
      1. 11.1.1 VCC Pins and Decoupling
        1. 11.1.1.1 Clock Output Supplies
        2. 11.1.1.2 Low-Crosstalk Supplies
        3. 11.1.1.3 PLL2 Supplies
        4. 11.1.1.4 Clock Input Supplies
        5. 11.1.1.5 Unused Clock Inputs/Outputs
    2. 11.2 Current Consumption / Power Dissipation Calculations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Thermal Management
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Development Support
        1. 13.1.1.1 PLLatinum Sim
        2. 13.1.1.2 TICS Pro
    2. 13.2 Related Links
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

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9.3.4 SYSREF to Device Clock Alignment

To ensure proper JESD204B operation, the timing relationship between the SYSREF and the device clock must be adjusted for optimum setup and hold time as shown in . The global SYSREF digital delay (SYSREF_DDLY). local SYSREF digital delay (SDCLKoutY_DDLY), local SYSREF half step (SDCLKoutY_HS), and local SYSREF analog delay (SDCLKoutY_ADLY, SDCLKoutY_ADLY_EN) can be adjusted to provide the required setup and hold time between SYSREF and device clock. It is also possible to adjust the device clock digital delay (DCLKoutX_DDLY_CNTH, DCLKoutX_DDLY_CNTL), device clock half step (DCLKoutX_HS), device clock analog delay (DCLKoutX_ADLY, DCLKoutX_ADLY_EN), and device clock muxes (DCLKoutX_MUX, DCLKoutX_ADLY_MUX) to adjust phase with respect to SYSREF.

LMK04821 LMK04826 LMK04828 SYSREF_DCLK_DDLY.pngFigure 16. SYSREF to Device Clock Timing Alignment

Depending on the settings for DCLKoutX and the SYSREF divider, some adjustment may be needed to correctly align DCLKoutX to SDCLKoutY. Equation 1 and Equation 2 predict the relative DCLKoutX to SDCLKoutY delay:

Equation 1. DELAYDCLK = DCLKoutX_DDLY_CNTH + DCLKoutX_DDLY_CNTL
Equation 2. DELAYSDCLK = SYSREF_DDLY + SDCLKoutY_DDLY + SYSREF_DIV_ADJUST + DCLKout_MUX_ADJUST

where

  • SYSREF_DIV_ADJUST = 2 IF (SYSREF_DIV % 4 < 2) ELSE 3
  • DCLKoutX_MUX_ADJUST = 1 IF (Duty Cycle Correction enabled) ELSE 0

For the relative delay equations, the cycle delay rather than the register value should be used, since cycle delay does not always equal register value (example: _CNTH/_CNTL=0, delay=16). Device clock duty cycle correction can be enabled for both digital and analog paths, either by setting DCLKoutX_MUX=1 (digital only), or by setting DCLKoutX_MUX=3 and DCLKoutX_ADLY_MUX=1. If half step is enabled on either path, delay can be included by subtracting 0.5 from the enabled path. As an example, if DCLKoutX_DDLY_CNTH=7, DCLKoutX_DDLY_CNTL=6, SYSREF_DDLY=8, SDCLKoutY_DDLY=2 cycles, SYSREF_DIV=30, DCLKoutX_MUX=1, DCLKoutX_HS=0, SDCLKoutX_HS=0:

  • DELAYDCLK = 7 + 6 = 13
  • SYSREF_DIV_ADJUST = (30 % 4 < 2) ? 2 : 3 = 3
  • DCLKoutX_MUX_ADJUST = DCC ? 1 : 0 = 0
  • DELAYSDCLK = 8 + 2 + 3 + 0 = 13

To calculate the expected time delay from the first edge of DCLKoutX to the first edge of SDCLKoutY, refer to Equation 3. Substitute the analog delays with the appropriate time values (in seconds) according to DCLKoutX_ADLY, DCLKoutX_ADLY_MUX, DCLKout_MUX and SDCLKoutY_ADLY_EN, SDCLKoutY_ADLY. tsJESD204B is provided in the Electrical Characteristics section for the conditions in the example above as -80 ps.

Equation 3. tDCLK-to-SDCLK = (FDistribution)-1 × (DELAYSDCLK - DELAYDCLK) + SDCLKoutY_ADLY - DCLKoutY_ADLY + tsJESD204B
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