SLVSBV8E June   2013  – February 2020 LMZ31704

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Application
  4. 4 Revision History
  5. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Package Specifications
    5. 5.5 Thermal Information
    6. 5.6 Electrical Characteristics
  6. 6 Device Information
    1. 6.1 Functional Block Diagram
    2.     Pin Functions
  7. 7 Typical Characteristics (PVIN = VIN = 12 V)
  8. 8 Typical Characteristics (PVIN = VIN = 5 V)
  9. 9 Typical Characteristics (PVIN = 3.3 V, VIN = 5 V)
  10. 10Application Information
    1. 10.1  Adjusting the Output Voltage
    2. 10.2  Capacitor Recommendations for the LMZ31704 Power Supply
      1. 10.2.1 Capacitor Technologies
        1. 10.2.1.1 Electrolytic, Polymer-Electrolytic Capacitors
        2. 10.2.1.2 Ceramic Capacitors
        3. 10.2.1.3 Tantalum, Polymer-Tantalum Capacitors
      2. 10.2.2 Input Capacitor
      3. 10.2.3 Output Capacitor
    3. 10.3  Transient Response
    4. 10.4  Transient Waveforms
    5. 10.5  Application Schematics
    6. 10.6  Custom Design With WEBENCH® Tools
    7. 10.7  VIN and PVIN Input Voltage
    8. 10.8  3.3 V PVIN Operation
    9. 10.9  Power Good (PWRGD)
    10. 10.10 SYNC_OUT
    11. 10.11 Parallel Operation
    12. 10.12 Light Load Efficiency (LLE)
    13. 10.13 Power-Up Characteristics
    14. 10.14 Pre-Biased Start-up
    15. 10.15 Remote Sense
    16. 10.16 Thermal Shutdown
    17. 10.17 Output On/Off Inhibit (INH)
    18. 10.18 Slow Start (SS/TR)
    19. 10.19 Overcurrent Protection
    20. 10.20 Synchronization (CLK)
    21. 10.21 Sequencing (SS/TR)
    22. 10.22 Programmable Undervoltage Lockout (UVLO)
    23. 10.23 Layout Considerations
    24. 10.24 EMI
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

Package Options

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

10.18 Slow Start (SS/TR)

Connecting the STSEL pin to AGND and leaving SS/TR pin open enables the internal SS capacitor with a slow start interval of approximately 1.2 ms. Adding additional capacitance between the SS pin and AGND increases the slow start time. Increasing the slow start time reduces inrush current seen by the input source and reduce the current seen by the device when charging the output capacitors. To avoid the activation of current limit and ensure proper start-up, the SS capacitor may need to be increased when operating near the maximum output capacitance limit.

Figure 29 shows an additional SS capacitor connected to the SS/TR pin and the STSEL pin connected to AGND. See Table 6 for SS capacitor values and timing interval.

LMZ31704 slvsAW7_SScap.gifFigure 29. Slow-Start Capacitor (CSS) and STSEL Connection

Table 6. Slow-Start Capacitor Values and Slow-Start Time

CSS (nF) OPEN 3.3 4.7 10 15 22 33
SS Time (msec) 1.2 2.1 2.5 3.8 5.1 7.0 9.8