SLUSAQ4G October   2011  – September 2022 TPS40422

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (continued)
  6. Pin Configuration and Functions
  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 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  PMBus Interface Protocol General Description
      2. 8.3.2  Voltage Reference
      3. 8.3.3  Output Voltage
      4. 8.3.4  Voltage Feed Forward
      5. 8.3.5  Current Sensing
      6. 8.3.6  Overcurrent Protection
      7. 8.3.7  Current Sharing
      8. 8.3.8  Linear Regulators
      9. 8.3.9  BP Switch-over
      10. 8.3.10 Switching Frequency Setting
      11. 8.3.11 Switching Node and BOOT Voltage
      12. 8.3.12 Reading the Output Current
      13. 8.3.13 Soft-Start Time
      14. 8.3.14 Turn-On/Turn-Off Delay and Sequencing
      15. 8.3.15 Pre-Biased Output Start-Up
      16. 8.3.16 Undervoltage Lockout
      17. 8.3.17 Overvoltage and Undervoltage Fault Protection
      18. 8.3.18 Power Good
      19. 8.3.19 Overtemperature Fault Protection
      20. 8.3.20 Thermal Shutdown
      21. 8.3.21 Programmable Fault Responses
      22. 8.3.22 User Data
      23. 8.3.23 Adjustable Anti-Cross Conduction Delay
      24. 8.3.24 Connection of Unused Pins
    4. 8.4 Device Functional Modes
      1. 8.4.1 Control Signal
      2. 8.4.2 OPERATION Command
      3. 8.4.3 Control Signal and OPERATION Command
      4. 8.4.4 Two-Phase Mode Operation
    5. 8.5 Programming
      1. 8.5.1 Supported PMBus Commands
        1. 8.5.1.1 PMBus Address
        2. 8.5.1.2 PMBus Connections
        3. 8.5.1.3 PMBus Data Format
        4. 8.5.1.4 PMBus Interface Output Voltage Adjustment
        5. 8.5.1.5 53
    6. 8.6 Register Maps
      1. 8.6.1 Supported Commands
        1. 8.6.1.1  PAGE (00h)
        2. 8.6.1.2  OPERATION (01h)
          1. 8.6.1.2.1 On
          2. 8.6.1.2.2 Margin
        3. 8.6.1.3  ON_OFF_CONFIG (02h)
          1. 8.6.1.3.1 pu
          2. 8.6.1.3.2 cmd
          3. 8.6.1.3.3 CPR
          4. 8.6.1.3.4 pol
          5. 8.6.1.3.5 CPA
        4. 8.6.1.4  CLEAR_FAULTS (03h)
        5. 8.6.1.5  WRITE_PROTECT (10h)
          1. 8.6.1.5.1 bit5
          2. 8.6.1.5.2 bit6
          3. 8.6.1.5.3 bit7
        6. 8.6.1.6  STORE_USER_ALL (15h)
        7. 8.6.1.7  RESTORE_USER_ALL (16h)
        8. 8.6.1.8  CAPABILITY (19h)
        9. 8.6.1.9  VOUT_MODE (20h)
          1. 8.6.1.9.1 Mode:
          2. 8.6.1.9.2 Exponent
        10. 8.6.1.10 VIN_ON (35h)
          1. 8.6.1.10.1 Exponent
          2. 8.6.1.10.2 Mantissa
        11. 8.6.1.11 VIN_OFF (36h)
          1. 8.6.1.11.1 Exponent
          2. 8.6.1.11.2 Mantissa
        12. 8.6.1.12 IOUT_CAL_GAIN (38h)
          1. 8.6.1.12.1 Exponent
          2. 8.6.1.12.2 Mantissa
        13. 8.6.1.13 IOUT_CAL_OFFSET (39h)
          1. 8.6.1.13.1 Exponent
          2. 8.6.1.13.2 Mantissa
        14. 8.6.1.14 IOUT_OC_FAULT_LIMIT (46h)
          1. 8.6.1.14.1 Exponent
          2. 8.6.1.14.2 Mantissa
        15. 8.6.1.15 IOUT_OC_FAULT_RESPONSE (47h)
          1. 8.6.1.15.1 RS[2:0]
        16. 8.6.1.16 IOUT_OC_WARN_LIMIT (4Ah)
          1. 8.6.1.16.1 Exponent
          2. 8.6.1.16.2 Mantissa
        17. 8.6.1.17 OT_FAULT_LIMIT (4Fh)
          1. 8.6.1.17.1 Exponent
          2. 8.6.1.17.2 Mantissa
        18. 8.6.1.18 OT_WARN_LIMIT (51h)
          1. 8.6.1.18.1 Exponent
          2. 8.6.1.18.2 Mantissa
        19. 8.6.1.19 TON_RISE (61h)
          1. 8.6.1.19.1 Exponent
          2. 8.6.1.19.2 Mantissa
        20. 8.6.1.20 STATUS_BYTE (78h)
        21. 8.6.1.21 STATUS_WORD (79h)
        22. 8.6.1.22 STATUS_VOUT (7Ah)
        23. 8.6.1.23 STATUS_IOUT (7Bh)
        24. 8.6.1.24 STATUS_TEMPERATURE (7Dh)
        25. 8.6.1.25 STATUS_CML (7Eh)
        26. 8.6.1.26 STATUS_MFR_SPECIFIC (80h)
        27. 8.6.1.27 READ_VOUT (8Bh)
        28. 8.6.1.28 READ_IOUT (8Ch)
          1. 8.6.1.28.1 Exponent
          2. 8.6.1.28.2 Mantissa
        29. 8.6.1.29 READ_TEMPERATURE_2 (8Eh)
          1. 8.6.1.29.1 Exponent
          2. 8.6.1.29.2 Mantissa
        30. 8.6.1.30 PMBUS_REVISION (98h)
        31. 8.6.1.31 MFR_SPECIFIC_00 (D0h)
        32. 8.6.1.32 VREF_TRIM (MFR_SPECIFIC_04) (D4h)
        33. 8.6.1.33 STEP_VREF_MARGIN_HIGH (MFR_SPECIFIC_05) (D5h)
        34. 8.6.1.34 STEP_VREF_MARGIN_LOW (MFR_SPECIFIC_06) (D6h)
        35. 8.6.1.35 PCT_VOUT_FAULT_PG_LIMIT (MFR_SPECIFIC_07) (D7h)
        36. 8.6.1.36 126
        37. 8.6.1.37 SEQUENCE_TON_TOFF_DELAY (MFR_SPECIFIC_08) (D8h)
        38. 8.6.1.38 128
        39. 8.6.1.39 OPTIONS (MFR_SPECIFIC_21) (E5h)
        40. 8.6.1.40 DEVICE_CODE (MFR_SPECIFIC_44) (FCh)
          1. 8.6.1.40.1 Identifier Code
          2. 8.6.1.40.2 Revision Code
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Dual-Output Converter
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Custom Design with WEBENCH® Tools
          2. 9.2.1.2.2 Step 1: Inductor Selection
          3. 9.2.1.2.3 Step 2: Output Capacitor Selection
          4. 9.2.1.2.4 Step 3: Input Capacitance Selection
          5. 9.2.1.2.5 Step 4: MOSFET Selection
          6. 9.2.1.2.6 Step 5: Snubber Circuit Design
          7. 9.2.1.2.7 Step 6: Soft-Start Time
          8. 9.2.1.2.8 Step 7: Peripheral Component Design
            1. 9.2.1.2.8.1 RT (Pin 1) Switching Frequency Setting
            2. 9.2.1.2.8.2 FB1 (Pin 2) and FB2 (Pin 8) Output Voltage Setting
            3. 9.2.1.2.8.3 Compensation Network Using COMP1 (Pin 3) , COMP2 (Pin 7), FB1 (Pin 2) FB2 DIFFO1 (Pin 8) (Pin 39)
            4. 9.2.1.2.8.4 Remote Sensing Using VSNS1 (Pin 37), GSNS1 (Pin 38) , VSNS2 (Pin 15), and GSNS2 (Pin 14)
            5. 9.2.1.2.8.5 Temperate Sensing Using TSNS1 (Pin36) and TSNS2 (Pin 16)
            6. 9.2.1.2.8.6 Current Sensing Network Design Using CS1P (Pin 34), CS1N (Pin 35) , CS2P (Pin 18), and CS2N (Pin 17)
            7. 9.2.1.2.8.7 PMBus Address ADDR1 (Pin 9) , and ADDR0 (Pin 10)
            8. 9.2.1.2.8.8 Voltage Decoupling Capacitors
              1. 9.2.1.2.8.8.1  VDD (Pin 31)
              2. 9.2.1.2.8.8.2  BP3 (Pin 32)
              3. 9.2.1.2.8.8.3  BNEXT (Pin 24)
              4. 9.2.1.2.8.8.4  BP6 (Pin 25)
              5. 9.2.1.2.8.8.5  Power Good PGOOD1 (Pin 33), PGOOD2 (Pin 19)
              6. 9.2.1.2.8.8.6  Bootstrap Capacitors BOOT1 (Pin 30), and BOOT2 (Pin 20)
              7. 9.2.1.2.8.8.7  High-Side MOSFET (Gate) Resistor
              8. 9.2.1.2.8.8.8  Synchronization Setting SYNC (Pin 40)
              9. 9.2.1.2.8.8.9  BP6 (Pin 25)
              10. 9.2.1.2.8.8.10 DIFFO (Pin 39)
        3. 9.2.1.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 PCB Layout Guidelines
      2. 11.1.2 MOSFET Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
Step 5: Snubber Circuit Design

The purpose of the snubber network is to damp the high frequency ringing on the switch node and reduce the peak voltage stress on the low-side FET. A quick and efficient way to design a snubber network is to base it off the allowable power budget to be dissipated. A best practice is to target power dissipation in the output snubber between 0.25% and 0.5% of total power. Normally, the R-C time constant is designed to be short enough such that the capacitor is fully charged or discharged before the next switching edge. In this case, the power dissipation in the snubber resistor is determined only by the capacitor value and independent of the resistor value.

Equation 27. GUID-24EB0CDF-AE3C-49EA-8901-BEA793EFE356-low.gif

where

  • peak voltage stored on the capacitors between pulse edges
  • tS is the period
  • fSW is the switching frequency
  • CS is the snubber capacitor

The power budget is 1.2 V × 20 A × 0.25% = 60 mW and because the switching frequency is 500 kHz with peak voltage of 14 V, the calculated effective snubber capacitor is 612pF. In this example, to make sure that the ringing is critically damped, a practical value is chosen to be 1000pF for C34 and C35.

In order to determine the resistor value, the fully charge and discharge time 5 × R × C is set to 10% of the shortest pulse width. Shortest pulse width can be determined using Equation 28.

Equation 28. GUID-4E72A417-B3E6-4EF4-AD31-460F875201F4-low.gif

In this design example, three 10-Ω resistors were chosen in parallel to obtain the calculated value and desired form factor. In the EVM schematic, the resistors are R30, R33, R20 and R29, R28, R26.