SLUSB94A OCTOBER   2012  – September 2016 TPS51716

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD 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  VDDQ Switch Mode Power Supply Control
      2. 7.3.2  VREF and REFIN, VDDQ Output Voltage
      3. 7.3.3  Soft-Start and Powergood
      4. 7.3.4  Power State Control
      5. 7.3.5  VDDQ Overvoltage and Undervoltage Protection
      6. 7.3.6  VDDQ Out-of-Bound Operation
      7. 7.3.7  VDDQ Overcurrent Protection
      8. 7.3.8  VTT and VTTREF
      9. 7.3.9  VTT Overcurrent Protection
      10. 7.3.10 V5IN Undervoltage Lockout (UVLO) Protection
      11. 7.3.11 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 MODE Pin Configuration
      2. 7.4.2 Discharge Control
      3. 7.4.3 D-CAP2 Mode Operation
      4. 7.4.4 Light-Load Operation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 External Components Selection
      3. 8.2.3 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 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Receiving Notification of Documentation Updates
      2. 11.2.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

TPS51716 is typically used as step down converters, which converts a voltage from 3V- 28V to 0.7 V to 1.8 V output voltage and provide a total solution to memory system.

8.2 Typical Application

TPS51716 v12148_lusb94.gif
(1) TI NexFET™ power MOSFETs are available and can be used in this application. Please contact your local TI representative.
Figure 25. DDR3, DCAP-2 500-kHz Application Circuit, Tracking Discharge

Table 3. DDR3, DCAP-2 500-kHz Application Circuit, List of Materials

REFERENCE DESIGNATOR QTY SPECIFICATION MANUFACTURE PART NUMBER
C8, C9 2 10 µF, 25 V Taiyo Yuden TMK325BJ106MM
C10 4 47 µF, 6.3 V TDK C2012X5R0J476M
L1 1 1 µH, 18.5 A, 2.3 mΩ NEC Tokin MPC1055L1R0C
Q1 1 30 V, 35 A, 8.5 mΩ Fairchild FDMS8680
Q2 1 30 V, 42 A, 3.5 mΩ Fairchild FDMS8670AS

8.2.1 Design Requirements

To begin the design process, the user must know a few application parameters (see Table 4).

Table 4. Design Parameters

PARAMETER EXAMPLE VALUE
Input voltage range 8 to 20 V
Output voltage 1. 5 V
Transient response, 1.5-A load step ΔVout = ±5%
Input ripple voltage 400 mV
Output ripple voltage 40 mV
Output current rating 10A
Operating frequency 670 kHz/ 500 kHz

8.2.2 Detailed Design Procedure

The following design procedure can be used to select component values for the TPS51716.

8.2.2.1 External Components Selection

The external components selection is a simple process.

  1. Determine the value of R1 and R2

    2. The output voltage is determined by the value of the voltage-divider resistor, R1 and R2. R1 is connected between VREF and REFIN pins, and R2 is connected between the REFIN pin and GND. Setting R1 to 10-kΩ is a good starting point. Determine R2 using Equation 5.

    Equation 5. TPS51716 q_r2_lusb94.gif

    For an application using organic semiconductor capacitor(s) or specialty polymer capacitor(s) for the output capacitor(s), the output voltage ripple can be calculated as shown in Equation 6.

    Equation 6. TPS51716 q_voutripple1_lusb94.gif

    For an application using ceramic capacitor(s) as the output capacitor(s), the output voltage ripple can be calculated as shown in Equation 7.

    Equation 7. TPS51716 q_voutripple2_lusb94.gif
  2. Choose the inductor

    3. The inductance value should be determined to yield a ripple current of approximately ¼ to ½ of maximum output current. Larger ripple current increases output ripple voltage and improves the signal-to-noise ratio and helps stable operation.

    Equation 8. TPS51716 q_lx_lusab9.gif

    The inductor needs a low direct current resistance (DCR) to achieve good efficiency, as well as enough room above peak inductor current before saturation. The peak inductor current can be estimated in Equation 9.

    Equation 9. TPS51716 q_iindpeak_lusae1.gif
  3. Choose the OCL setting resistance, RTRIP

    4. Combining Equation 1 and Equation 2, RTRIP can be obtained using Equation 10.

    Equation 10. TPS51716 q_rtrip1_lusab9.gif
  4. Choose the output capacitors

    5. Determine output capacitance to meet small signal stability as shown in Equation 11.

    Equation 11. TPS51716 q_3timesfp_lusae1.gif

    where

    • RC × CC time constant is 23 µs for 500 kHz operation (or 14.6 µs for 670-kHz operation)
    • G = 0.25

8.2.3 Application Curves

TPS51716 wave3_lusab9.png
Figure 26. 1.5-V Startup Waveforms
TPS51716 wave5_lusab9.png
Figure 28. 1.5-V Soft-Stop Waveforms (Tracking Discharge)
TPS51716 wave4_lusab9.png
Figure 27. 1.5-V Startup Waveforms (0.5-V Pre-Biased)
TPS51716 wave6_lusab9.png
Figure 29. 1.5-V Soft-Stop Waveforms (Non-Tracking Discharge)
TPS51716 vddq_bode_lusae1.png
Figure 30. VDDQ Bode Plot
TPS51716 bodeplus1a_lusab9.png
Figure 32. VTT Bode Plot (Source)
TPS51716 bodeminus1a_lusab9.png
Figure 31. VTT Bode Plot (Sink)