SLUS609J May   2004  – January 2018 TPS51116

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1. 3.1 Typical Application
  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 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Dissipation Ratings
    5. 6.5 Thermal Information
    6. 6.6 Electrical Characteristics
    7. 6.7 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  VDDQ SMPS, Light Load Condition
      2. 7.3.2  Low-Side Driver
      3. 7.3.3  High-Side Driver
      4. 7.3.4  Current Sensing Scheme
      5. 7.3.5  PWM Frequency and Adaptive On-Time Control
      6. 7.3.6  VDDQ Output Voltage Selection
      7. 7.3.7  VTT Linear Regulator and VTTREF
      8. 7.3.8  Controling Outputs Using the S3 and S5 Pins
      9. 7.3.9  Soft-Start Function and Powergood Status
      10. 7.3.10 VDDQ and VTT Discharge Control
      11. 7.3.11 Current Protection for VDDQ
      12. 7.3.12 Current Protection for VTT
      13. 7.3.13 Overvoltage and Undervoltage Protection for VDDQ
      14. 7.3.14 Undervoltage Lockout (UVLO) Protection, V5IN (PWP), V5FILT (RGE)
      15. 7.3.15 Input Capacitor, V5IN (PWP), V5FILT (RGE)
      16. 7.3.16 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 VDDQ SMPS, Dual PWM Operation Modes
      2. 7.4.2 Current Mode Operation
      3. 7.4.3 D-CAP™ Mode Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 DDR3 Application With Current Mode
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Pin Connections
        2. 8.2.2.2 Choose the inductor
        3. 8.2.2.3 Choose rectifying (low-side) MOSFET
        4. 8.2.2.4 Choose output capacitance
        5. 8.2.2.5 Determine f0 and calculate RC
        6. 8.2.2.6 Calculate CC2
        7. 8.2.2.7 Calculate CC.
        8. 8.2.2.8 Determine the value of R1 and R2.
      3. 8.2.3 Application Curves
    3. 8.3 DDR3 Application With D−CAP™ Mode
      1. 8.3.1 Design Requirements
      2. 8.3.2 Detailed Design Procedure
        1. 8.3.2.1 Pin Connections
        2. 8.3.2.2 Choose the Components
      3. 8.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGE|24
  • PWP|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.9 Soft-Start Function and Powergood Status

The soft-start function of the SMPS is achieved by ramping up reference voltage and two-stage current clamp. At the starting point, the reference voltage is set to 650 mV (87% of its target value) and the overcurrent threshold is set half of the nominal value. When UVP comparator detects VDDQ become greater than 80% of the target, the reference voltage is raised toward 750 mV using internal 4-bit DAC. This takes approximately 85 μs. The overcurrent threshold is released to nominal value at the end of this period. The powergood signal waits another 45 μs after the reference voltage reaches 750 mV and the VDDQ voltage becomes good (above 95% of the target voltage), then turns off powergood open-drain MOSFET.

The soft-start function of the VTT LDO is achieved by current clamp. The current limit threshold is also changed in two stages using an internal powergood signal dedicated for LDO. During VTT is below the powergood threshold, the current limit level is cut into 60% (2.2 A).This allows the output capacitors to be charged with low and constant current that gives linear ramp up of the output. When the output comes up to the good state, the overcurrent limit level is released to normal value (3.8 A). The device has an independent counter for each output, but the PGOOD signal indicates the status of VDDQ only and does not indicate VTT powergood status externally. See Figure 35.

TPS51116 v04066_lus609.gifFigure 35. VDDQ Soft-Start and Powergood Timing

Soft-start duration, tVDDQSS, tVTTSS are functions of output capacitances.

Equation 2. TPS51116 q_tvddqss_lus609.gif

where

  • IVDDQOCP is the current limit value for VDDQ switcher calculated by Equation 5
Equation 3. TPS51116 q_tvttss_lus609.gif

where

  • IVTTOCL = 2.2 A (typ)

In both Equation 2 and Equation 3 , no load current during start-up are assumed. Note that both switchers and the LDO do not start up with full load condition.