SLUSAS9B NOVEMBER   2013  – December 2014 TPS53915

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. 6.7 Thermal Performance
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1  Powergood
      2. 7.3.2  D-CAP3 Control and Mode Selection
      3. 7.3.3  D-CAP3 Mode
      4. 7.3.4  Sample and Hold Circuitry
      5. 7.3.5  Adaptive Zero-Crossing
      6. 7.3.6  Forced Continuous-Conduction Mode
      7. 7.3.7  Current Sense and Overcurrent Protection
      8. 7.3.8  Overvoltage and Undervoltage Protection
      9. 7.3.9  Out-Of-Bounds Operation (OOB)
      10. 7.3.10 UVLO Protection
      11. 7.3.11 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Auto-Skip Eco-Mode Light-Load Operation
      2. 7.4.2 Forced Continuous-Conduction Mode
    5. 7.5 Programming
      1. 7.5.1  The PMBus General Descriptions
      2. 7.5.2  PMBus Slave Address Selection
      3. 7.5.3  PMBus Address Selection
      4. 7.5.4  Supported Formats
        1. 7.5.4.1 Direct Format: Write
        2. 7.5.4.2 Combined Format: Read
        3. 7.5.4.3 Stop-Separated Reads
      5. 7.5.5  Supported PMBus Commands
        1. 7.5.5.1 Unsupported PMBus Commands
        2. 7.5.5.2 OPERATION [01h] (R/W Byte)
        3. 7.5.5.3 ON_OFF_CONFIG [02h] (R/W Byte)
        4. 7.5.5.4 WRITE_PROTECT [10h] (R/W Byte)
      6. 7.5.6  CLEAR_FAULTS [03h] (Send Byte)
      7. 7.5.7  STORE_DEFAULT_ALL [11h] (Send Byte)
      8. 7.5.8  RESTORE_DEFAULT_ALL [12h] (Send Byte)
      9. 7.5.9  STATUS_WORD [79h] (Read Word)
      10. 7.5.10 CUSTOM_REG (MFR_SPECIFIC_00) [D0h] (R/W Byte)
      11. 7.5.11 DELAY_CONTROL (MFR_SPECIFIC_01) [D1h] (R/W Byte)
      12. 7.5.12 MODE_SOFT_START_CONFIG (MFR_SPECIFIC_02) [D2h] (R/W Byte)
      13. 7.5.13 FREQUENCY_CONFIG (MFR_SPECIFIC_03) [D3h] (R/W Byte)
      14. 7.5.14 VOUT_ADJUSTMENT (MFR_SPECIFIC_04) [D4h] (R/W Byte)
      15. 7.5.15 Output Voltage Fine Adjustment Soft Slew Rate
      16. 7.5.16 VOUT_MARGIN (MFR_SPECIFIC_05) [D5h] (R/W Byte)
      17. 7.5.17 Output Voltage Margin Adjustment Soft-Slew Rate
      18. 7.5.18 UVLO_THRESHOLD (MFR_SPECIFIC_06) [D6h]
  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 Choose the Switching Frequency
        2. 8.2.2.2 Choose the Operation Mode
        3. 8.2.2.3 Choose the Inductor
        4. 8.2.2.4 Choose the Output Capacitor
        5. 8.2.2.5 Determine the Value of R1 and R2
      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 Documentation Support
    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 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

The TPS53915 device is a high-efficiency, single-channel, synchronous-buck converter. The device suits low-output voltage point-of-load applications with 12-A or lower output current in computing and similar digital consumer applications.

8.2 Typical Application

typ_app_slusas9.gifFigure 52. Typical Application Circuit Diagram

8.2.1 Design Requirements

This design uses the parameters listed in Table 19.

Table 19. Design Example Specifications

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
INPUT CHARACTERISTICS
VIN Voltage range 5 12 18 V
IMAX Maximum input current V IN = 5 V, I OUT = 8 A 2.5 A
No load input current V IN = 12 V, I OUT = 0 A with auto skip mode 1 mA
OUTPUT CHARACTERISTICS
VOUT Output voltage 1.2 V
Output voltage regulation Line regulation, 0.2% 5 V ≤ V IN ≤ – 14 V with FCCM 0.2%
Load regulation, 0.5% V IN = 12 V, 0 A ≤ I OUT ≤ 8 A with FCCM 0.5%
VRIPPLE Output voltage ripple V IN = 12 V, I OUT = 8 A with FCCM 10 mV PP
ILOAD Output load current 0 8 A
IOVER Output over current 11
tSS Soft-start time 1 ms
SYSTEM CHARACTERISTICS
fSW Switching frequency 500 kHz
η Peak efficiency V IN = 12 V, V OUT = 1.2 V ,I OUT = 4 A 88.5%
Full load efficiency V IN = 12 V, V OUT = 1.2 V , I OUT = 8 A 88.9%
TA Operating temperature 25 ºC

8.2.2 Detailed Design Procedure

The external components selection is a simple process using D-CAP3 Mode. Select the external components using the following steps.

8.2.2.1 Choose the Switching Frequency

The default switching frequency (fSW) is pre-set at 400 kHz. The switching frequency can be changed through PMBus function MFR_SPECIFIC_03 (see Table 13).

8.2.2.2 Choose the Operation Mode

Select the operation mode using Table 3.

8.2.2.3 Choose the Inductor

Determine the inductance value to set the ripple current at approximately ¼ to ½ of the maximum output current. Larger ripple current increases output ripple voltage, improves signal-to-noise ratio, and helps to stabilize operation.

Equation 6. q_de_l_slusbq8.gif

The inductor requires a low DCR to achieve good efficiency. The inductor also requires enough room above peak inductor current before saturation. The peak inductor current is estimated using Equation 7.

Equation 7. q_de_iindpeak_slusbq8.gif

8.2.2.4 Choose the Output Capacitor

The output capacitor selection is determined by output ripple and transient requirement. When operating in CCM, the output ripple has two components as shown in Equation 8. Equation 9 and Equation 10 define these components.

Equation 8. q_vripple_slusbn5.gif
Equation 9. q_vripplec_slusbn5.gif
Equation 10. q_vrippleesr_slusbn5.gif

8.2.2.5 Determine the Value of R1 and R2

The output voltage is programmed by the voltage-divider resistors, R1 and R2, shown in Equation 11. Connect R1 between the VFB pin and the output, and connect R2 between the VFB pin and GND. The recommended R2 value is from 1 kΩ to 20 kΩ. Determine R1 using Equation 11.

Equation 11. q_de_r1_slusbq8.gif

8.2.3 Application Curves

C004_SLUSBN5.pngFigure 53. Efficiency vs. Output Current
C009_SLUSBN5.pngFigure 55. Output Voltage vs. Output Current
startup_6a_slusbq8.gif
ILOAD = 6 A
Figure 57. Start-Up Sequence
transient_0a6a_slusbq8.gif
ILOAD from 0 A to 6 A
Figure 59. Load Transient
transient_0a6a0a_slusbq8.gif
ILOAD from 0 A to 6A to 0 A
Figure 61. Full Cycle Load Transient
transient_vripple_6a_slusbq8.gif
ILOAD = 6 A
Figure 63. Output Voltage Ripple
C008_SLUSBN5.pngFigure 54. Output Voltage vs. Output Current
C012_SLUSBN5.pngFigure 56. Switching Frequency vs. Output Current
shutdown_6a_slusbq8.gif
ILOAD = 6 A
Figure 58. Shutdown Sequence
transient_6a0a_slusbq8.gif
ILOAD from 6A to 0 A
Figure 60. Load Transient
transient_vripple_0a_slusbq8.gif
ILOAD = 0 A
Figure 62. Output Voltage Ripple
transient_prebias_slusbq8.gif
Preset VOUT = 0.5 V
Figure 64. Pre-Bias Start-Up