SLUSBO6C JANUARY   2014  – October 2018 TPS40425

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1. 3.1 Simplified Application Diagram (Dual Output)
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Asynchronous Pulse Injection (API)
      2. 7.3.2  Adaptive Voltage Scaling (AVS)
      3. 7.3.3  Switching Frequency and Synchronization
      4. 7.3.4  Voltage Reference
      5. 7.3.5  Output Voltage and Remote Sensing Amplifier
      6. 7.3.6  Current Sensing and Temperature Sensing Modes
        1. 7.3.6.1 Non Smart-Power Operation
        2. 7.3.6.2 Smart-Power Operation.
      7. 7.3.7  Current Sensing
      8. 7.3.8  Temperature Sensing
      9. 7.3.9  Current Sharing
      10. 7.3.10 Linear Regulators
      11. 7.3.11 Power Sequence Between TPS40425 Device and Power Stage
      12. 7.3.12 PWM Signal
        1. 7.3.12.1 PWM Behavior During Soft-start Operation
      13. 7.3.13 Startup and Shutdown
      14. 7.3.14 Pre-Biased Output Start-up
      15. 7.3.15 PGOOD Indication
      16. 7.3.16 Overcurrent Protection
      17. 7.3.17 Overvoltage/Undervoltage Protection
      18. 7.3.18 Overtemperature Fault Protection
      19. 7.3.19 Input Undervoltage Lockout (UVLO)
      20. 7.3.20 Fault Communication
      21. 7.3.21 Fault Protection Summary
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 Multi-Phase Applications
    6. 7.6 Register Maps
      1. 7.6.1 PMBus General Description
      2. 7.6.2 PMBus Functionality
        1. 7.6.2.1 PMBus Address
        2. 7.6.2.2 PMBus Connections
        3. 7.6.2.3 PMBus Data Format
        4. 7.6.2.4 PMBus Output Voltage Adjustment
          1. 7.6.2.4.1 No Margin Voltage
          2. 7.6.2.4.2 Margin High Voltage State
          3. 7.6.2.4.3 Margin Low State
      3. 7.6.3 Reading the Output Current
      4. 7.6.4 Soft-Start Time
      5. 7.6.5 Turn-On/Turn-Off Delay and Sequencing
    7. 7.7 Supported PMBus Commands
      1. 7.7.1  PAGE (00h)
      2. 7.7.2  OPERATION (01h)
      3. 7.7.3  ON_OFF_CONFIG (02h)
      4. 7.7.4  CLEAR_FAULTS (03h)
      5. 7.7.5  WRITE_PROTECT (10h)
      6. 7.7.6  STORE_USER_ALL (15h)
      7. 7.7.7  RESTORE_USER_ALL (16h)
      8. 7.7.8  CAPABILITY (19h)
      9. 7.7.9  VOUT_MODE (20h)
      10. 7.7.10 VIN_ON (35h)
      11. 7.7.11 VIN_OFF (36h)
      12. 7.7.12 IOUT_CAL_GAIN (38h)
      13. 7.7.13 IOUT_CAL_OFFSET (39h)
      14. 7.7.14 IOUT_OC_FAULT_LIMIT (46h)
      15. 7.7.15 IOUT_OC_FAULT_RESPONSE (47h)
      16. 7.7.16 IOUT_OC_WARN_LIMIT (4Ah)
      17. 7.7.17 OT_FAULT_LIMIT (4Fh)
      18. 7.7.18 OT_WARN_LIMIT (51h)
      19. 7.7.19 TON_RISE (61h)
      20. 7.7.20 STATUS_BYTE (78h)
      21. 7.7.21 STATUS_WORD (79h)
      22. 7.7.22 STATUS_VOUT (7Ah)
      23. 7.7.23 STATUS_IOUT (7Bh)
      24. 7.7.24 STATUS_TEMPERATURE (7Dh)
      25. 7.7.25 STATUS_CML (7Eh)
      26. 7.7.26 STATUS_MFR_SPECIFIC (80h)
      27. 7.7.27 READ_VOUT (8Bh)
      28. 7.7.28 READ_IOUT (8Ch)
      29. 7.7.29 READ_TEMPERATURE_2 (8Eh)
      30. 7.7.30 PMBus_REVISION (98h)
      31. 7.7.31 MFR_SPECIFIC_00 (D0h)
      32. 7.7.32 MFR_SPECIFIC_04 (VREF_TRIM) (D4h)
      33. 7.7.33 MFR_SPECIFIC_05 (STEP_VREF_MARGIN_HIGH) (D5h)
      34. 7.7.34 MFR_SPECIFIC_06 (STEP_VREF_MARGIN_LOW) (D6h)
      35. 7.7.35 MFR_SPECIFIC_07 (PCT_VOUT_FAULT_PG_LIMIT) (D7h)
      36. 7.7.36 MFR_SPECIFIC_08 (SEQUENCE_TON_TOFF_DELAY) (D8h)
      37. 7.7.37 MFR_SPECIFIC_16 (COMM_EEPROM_SPARE) (E0h)
      38. 7.7.38 MFR_SPECIFIC_21 (OPTIONS) (E5h)
      39. 7.7.39 MFR_SPECIFIC_22 (PWM_OSC_SELECT) (E6h)
      40. 7.7.40 MFR_SPECIFIC_23 (MASK SMBALERT) (E7h)
      41. 7.7.41 MFR_SPECIFIC_25 (AVS_CONFIG) (E9h)
      42. 7.7.42 MFR_SPECIFIC_26 (AVS_ADDRESS) (EAh)
      43. 7.7.43 MFR_SPECIFIC_27 (AVS_DAC_DEFAULT) (EBh)
      44. 7.7.44 MFR_SPECIFIC_28 (AVS_CLAMP_HI) (ECh)
      45. 7.7.45 MFR_SPECIFIC_29 (AVS_CLAMP_LO) (EDh)
      46. 7.7.46 MFR_SPECIFIC_30 (TEMP_OFFSET) (EEh)
      47. 7.7.47 MFR_SPECIFIC_32 (API_OPTIONS) (F0h)
      48. 7.7.48 MFR_SPECIFIC_44 (DEVICE_CODE) (FCh)
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Dual-Output Application
      2. 8.2.2 Design Requirements
      3. 8.2.3 Design Procedure
        1. 8.2.3.1  Switching Frequency Selection
        2. 8.2.3.2  Inductor Selection
        3. 8.2.3.3  Output Capacitor Selection
          1. 8.2.3.3.1 Output Voltage Deviation During Load Transient
          2. 8.2.3.3.2 Output Voltage Ripple
        4. 8.2.3.4  Input Capacitor Selection
        5. 8.2.3.5  VDD, BP5, BP3 Bypass Capacitor
        6. 8.2.3.6  R-C Snubber
        7. 8.2.3.7  Current and Temperature Sensor
        8. 8.2.3.8  Power Sequence Between the TPS40425 Device and Power Stage
        9. 8.2.3.9  Output Voltage Setting and Frequency Compensation Selection
        10. 8.2.3.10 Key PMBus Parameter Selection
          1. 8.2.3.10.1 MFR_SPECIFIC_21 (OPTIONS)
            1. 8.2.3.10.1.1 IOUT_CAL_GAIN
            2. 8.2.3.10.1.2 Enable and UVLO
            3. 8.2.3.10.1.3 Soft-Start Time
            4. 8.2.3.10.1.4 Overcurrent Threshold and Response
      4. 8.2.4 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Layout Guidelines for TPS40425 Device
      2. 10.1.2 Layout Guidelines for Power Stage Device
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Texas Instruments Fusion Digital Power Designer
        2. 11.1.1.2 TPS40k Loop Compensation Tool
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.3.2 Inductor Selection

Use Equation 11 to calculate the value of the output inductance. The coefficient KIND represents the amount of inductor ripple current relative to the maximum output current. The output capacitor filters the inductor ripple current. Therefore, choosing a high inductor ripple current impacts the selection of the output capacitor since the output capacitor must have a ripple current rating equal to or greater than the inductor ripple current. Generally, maintain the KIND coefficient between 0.2 and 0.3 for balanced performance. Using this target ripple current, Equation 11 describes the required inductor size calculation.

Equation 11. TPS40425 q_de_l1_slusbv0.gif

With a selected KIND of 0.25, the target inductance (L1) calcualtes to 351 nH. Considering the variation and de-rating of inductance, this application uses a 470-nH inductor (Wurth Electronics part number 744355147). Equation 12 calculates the inductor ripple current . Equation 13 calculates the RMS current. Equation 13 calculates the peak current. Use these values to select an inductor with the approximate target inductance value, and to select current ratings that allow normal operation with some margin.

Equation 12. TPS40425 q_de_lripple_slusbv0.gif
Equation 13. TPS40425 q_de_llrms_slusbv0.gif
Equation 14. TPS40425 q_de_llpeak_slusbv0.gif

The WE 744355147 inductor is rated for 30 A RMS current and 50 A saturation current. Using this inductor, the ripple current IRIPPLE = 4.7 A, the RMS inductor current IL(rms) = 25.04 A, and peak inductor current IL(peak) = 27.33 A.