SLVSDJ1A July   2016  – May 2017 TPS65381A-Q1


  1. Device Overview
    1. 1.1 Features
    2. 1.2 Applications
    3. 1.3 Description
    4. 1.4 Typical Application Diagram
  2. Revision History
  3. Pin Configuration and Functions
  4. Specifications
    1. 4.1 Absolute Maximum Ratings
    2. 4.2 ESD Ratings
    3. 4.3 Recommended Operating Conditions
    4. 4.4 Thermal Information
    5. 4.5 Electrical Characteristics
    6. 4.6 Timing Requirements
    7. 4.7 Switching Characteristics
    8. 4.8 Typical Characteristics
  5. Detailed Description
    1. 5.1 Overview
    2. 5.2 Functional Block Diagram
    3. 5.3 Feature Description
      1. 5.3.1 VDD6 Buck Switch-Mode Power Supply
      2. 5.3.2 VDD5 Linear Regulator
      3. 5.3.3 VDD3/5 Linear Regulator
      4. 5.3.4 VDD1 Linear Regulator
      5. 5.3.5 VSOUT1 Linear Regulator
      6. 5.3.6 Charge Pump
      7. 5.3.7 Wake-Up
      8. 5.3.8 Reset Extension
    4. 5.4 Device Functional Modes
      1. 5.4.1  Power-Up and Power-Down Behavior
      2. 5.4.2  Safety Functions and Diagnostics Overview
      3. 5.4.3  Voltage Monitor (VMON)
      4. 5.4.4  TPS65381A-Q1 Internal Error Signals
      5. 5.4.5  Loss-of-Clock Monitor (LCMON)
      6. 5.4.6  Analog Built-In Self-Test (ABIST)
      7. 5.4.7  Logic Built-In Self-Test (LBIST)
      8. 5.4.8  Junction Temperature Monitoring and Current Limiting
      9. 5.4.9  Diagnostic MUX and Diagnostic Output Pin (DIAG_OUT)
        1. Analog MUX (AMUX)
        2. Digital MUX (DMUX)
        3. Diagnostic MUX Output State (by MUX_OUT bit)
        4. MUX Interconnect Check
      10. 5.4.10 Watchdog Timer (WD)
      11. 5.4.11 Watchdog Fail Counter, Status, and Fail Event
      12. 5.4.12 Watchdog Sequence
      13. 5.4.13 MCU to Watchdog Synchronization
      14. 5.4.14 Trigger Mode (Default Mode)
      15. 5.4.15 Q&A Mode
        1. Watchdog Q&A Related Definitions
        2. Watchdog Sequence in Q&A Mode
        3. Question (Token) Generation
        4. Answer Comparison and Reference Answer
          1. Sequence of the 2-bit Watchdog Answer Counter
        5. Watchdog Q&A Mode Sequence Events and WD_STATUS Register Updates
      16. 5.4.16 MCU Error Signal Monitor (MCU ESM)
        1. TMS570 Mode
        2. PWM Mode
      17. 5.4.17 Device Configuration Register Protection
      18. 5.4.18 Enable and Reset Driver Circuit
      19. 5.4.19 Device Operating States
      20. 5.4.20 STANDBY State
      21. 5.4.21 RESET State
      22. 5.4.22 DIAGNOSTIC State
      23. 5.4.23 ACTIVE State
      24. 5.4.24 SAFE State
      25. 5.4.25 State Transition Priorities
      26. 5.4.26 Power on Reset (NPOR)
    5. 5.5 Register Maps
      1. 5.5.1 Serial Peripheral Interface (SPI)
        1. SPI Command Transfer Phase
        2. SPI Data-Transfer Phase
        3. Device Status Flag Byte Response
        4. Device SPI Data Response
        5. SPI Frame Overview
      2. 5.5.2 SPI Register Write Access Lock (SW_LOCK command)
      3. 5.5.3 SPI Registers (SPI Mapped Response)
        1. Device Revision and ID
          1. DEV_REV Register
          2. DEV_ID Register
        2. Device Status
          1. DEV_STAT Register
        3. Device Configuration
          1. DEV_CFG1 Register
          2. DEV_CFG2 Register
      4. 5.5.4 Device Safety Status and Control Registers
        1.  VMON_STAT_1 Register
        2.  VMON_STAT_2 Register
        3.  SAFETY_STAT_1 Register
        4.  SAFETY_STAT_2 Register
        5.  SAFETY_STAT_3 Register
        6.  SAFETY_STAT_4 Register
        7.  SAFETY_STAT_5 Register
        8.  SAFETY_ERR_CFG Register
        9.  SAFETY_BIST_CTRL Register
        10. SAFETY_CHECK_CTRL Register
        11. SAFETY_FUNC_CFG Register
        12. SAFETY_ERR_STAT Register
        13. SAFETY_ERR_PWM_H Register
        14. SAFETY_ERR_PWM_L Register
        15. SAFETY_PWD_THR_CFG Register
        16. SAFETY_CFG_CRC Register
        17. Diagnostics
          1. DIAG_CFG_CTRL Register
          2. DIAG_MUX_SEL Register
      5. 5.5.5 Watchdog Timer
        1. WD_TOKEN_FDBK Register
        2. WD_WIN1_CFG Register
        3. WD_WIN2_CFG Register
        4. WD_TOKEN_VALUE Register
        5. WD_STATUS Register
        6. WD_ANSWER Register
      6. 5.5.6 Sensor Supply
        1. SENS_CTRL Register
  6. Application and Implementation
    1. 6.1 Application Information
    2. 6.2 Typical Application
      1. 6.2.1 Design Requirements
      2. 6.2.2 Detailed Design Procedure
        1. VDD6 Preregulator
        2. VDD1 Linear Controller
        3. VSOUT1 Tracking Linear Regulator, Configured to Track VDD5
        4. Alternative Use for VSOUT1 Tracking Linear Regulator, Configured for 6-V Output Tracking VDD3/5 In 3.3-V Mode
        5. Alternative Use for VSOUT1 Tracking Linear Regulator, Configured for 9-V Output Tracking to 5-V Input from VDD5
        6. Alternative Use for VSOUT1 Tracking Linear Regulator, Configured in Non-tracking Mode Providing a 4.5-V Output
      3. 6.2.3 Application Curves
    3. 6.3 System Examples
  7. Power Supply Recommendations
  8. Layout
    1. 8.1 Layout Guidelines
      1. 8.1.1 VDD6 Buck Preregulator
      2. 8.1.2 VDD1 Linear Regulator Controller
      3. 8.1.3 VDD5 and VDD3/5 Linear Regulators
      4. 8.1.4 VSOUT1 Tracking Linear Regulator
      5. 8.1.5 Charge Pump
      6. 8.1.6 Other Considerations
    2. 8.2 Layout Example
    3. 8.3 Power Dissipation and Thermal Considerations
  9. Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Community Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

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


Layout Guidelines

VDD6 Buck Preregulator

  • Minimize the loop area for the switching loop of the inductor, ESR resistor, output capacitor, and diode.
  • Minimize the parasitic trace impedance by using traces that are as wide as possible.
  • Minimize the parasitic via impedance by using multiple vias, especially on high current and switching nodes.
  • Connect the inductor and diode to SDN6 as close as possible to the pin.
  • Connect the diode to PGND (ground plane).
  • Connect the ESR resistor and output capacitor in series between VDD6 output (inductor output) and PGND.
  • Connect the EMC filter capacitor between VDD6 output and PGND.
  • Connect the VDD6 output to the VDD6 pin with routing to avoid coupling switching noise. Trace length should be minimized and as wide a trace as possible. This trace is the supply input to the downstream regulators using VDD6 as a preregulator, parasitic impedance should be minimized.

Additional consideration: add a footprint for a RC snubber circuit if one is required for the application. The RC connects in-series between the SDN6 and PGND pins.

VDD1 Linear Regulator Controller

  • Connect the drain of the external FET to VDD6 node, the trace should be minimized so that additional downstream buffering capacitors are not needed.
  • Connect the output capacitor to the source of the external FET, the length of this trace should be minimized. Connect the output capacitor to the ground plane.
  • Connect the gate drive, VDD1_G, to the gate of the FET. Connect the resistor between the gate of the FET and the source of the FET, minimize the trace length.
  • The resistor divider for sensing and setting the output voltage connects between the source of the FET (VDD1 output) and GND (device signal ground). Do not locate these components and their traces near the switching nodes or high-current traces.

VDD5 and VDD3/5 Linear Regulators

Connect the output capacitor as close as possible between the VDDx output and GND.

VSOUT1 Tracking Linear Regulator

  • Connect the output capacitor as close as possible between the VSOUT1 output and GND.
  • The resistor divider for sensing and setting the output voltage connects between the VSOUT1 and GND (device signal ground). Do not locate these components and their traces near the switching nodes or high-current traces.
  • Connect the local decoupling capacitor between the VSIN and PGND pins. Minimize trace length.
  • Route the tracking supply signal, connected to VTRACK1, away from switching nodes or high-current traces.

Charge Pump

  • Connect the capacitor as close as possible between the CP1 and CP2 pins.
  • Connect the capacitor between the VCP pin and VBATP (reverse protected and filtered) supply.

Other Considerations

  • Use ground planes. TI recommends having a solid ground plane and connect GND and PGND with as low impendence paths as possible to the ground plane.
  • Minimize parasitic impedance on the critical switching and high current paths.
  • Short PGNDx and GND to the thermal pad.
  • Use a star ground configuration if connecting to a non-ground plane system. Use tie-ins for the voltage-sense feedback ground and local biasing bypass capacitor ground networks to this star ground.
  • Connect the local decoupling capacitor between VBATP and PGND. Minimize trace length.

Layout Example

TPS65381A-Q1 layout_slvsbc4.gif Figure 8-1 TPS65381A-Q1 Board Layout

Power Dissipation and Thermal Considerations

The power dissipation of the device in the application has significant impact on the necessary layout and thermal management strategy of the application.

Use the following equations to calculate the estimated power dissipation in the device:

Equation 1. PVDD6 = (1 – effVDD6) × 6 V × IVDD6


  • PVDD6 is a conservative estimation of the power dissipation of VDD6 in the device because some of the efficiency loss is externally in the diode and inductor. A more accurate power estimator is available in the TPS65381-Q1 and TPS65381A-Q1 Power Estimator.
  • effVDD6 is the efficiency of VDD6 buck preregulator according to Figure 8-2 .
  • IVDD6 is the total load current from VDD5, VDD3/5, VDD1, VSOUT1 and any external load connected to VDD6.
Equation 2. PVDD5 = (6 V – 5 V) × IVDD5 = 1 V × IVDD5


  • IVDD5 is the load current on VDD5.
Equation 3. PVDD3/5 = (6 V – VVDD3/5) × IVDD3/5


  • VVDD3/5 is either 3.3 V or 5 V.
  • IVDD3/5 is the load current on VDD3/5.
Equation 4. PVSOUT1 = (VVSIN – VVSOUT1) × IVSOUT1


  • VVSIN is either 6 V (VDD6) or VBATP.
  • VVSOUT1 is the programmed output voltage of VSOUT1.
  • IVSOUT1 is the load current on VSOUT1
Equation 5. PTOT = PVDD6 + PVDD5 + PVDD3/5 + PVSOUT1


  • PTOT is the total power dissipation in the device.
TPS65381A-Q1 D001_slvsbc4.gif Figure 8-2 Typical VDD6 BUCK Efficiency

The useful range of device operation is affected by the supply voltage, application load-current requirements, and the thermal characteristics of the package and printed circuit board (PCB). For the device to be useful over a wide temperature range, the package, PCB and thermal management strategy must allow for the effective removal of the produce heat to keep junction temperature of the device within rated limits.

Use Equation 1 to Equation 5 to calculate the estimated power dissipation. As shown by the equation for VDD6 power dissipation (PVDD6), Equation 2, a large portion of the power dissipation is determined by the efficiency of the VDD6 supply. The efficiency of the VDD6 supply depends on load current and supply voltage as shown in Equation 2.

The 32-pin HTSSOP PowerPAD (DAP) offers an effective means of removing heat from the device junction. As described in PowerPad™ Thermally Enhanced Package, the PowerPAD package offers a lead-frame die pad that is exposed at the base of the package. This thermal pad must be soldered to the copper on the PCB directly underneath the package to create an effective path for removal of heat from the device, and, therefore, to reduce the RθJC. The PCB must be designed with thermal lands and thermal vias to complete the heat removal subsystem, as summarized in PowerPAD™ Made Easy and A Guide to Board Layout for Best Thermal Resistance for Exposed Packages.

Figure 8-3 shows the thermal derating profile of the 32-pin HTSSOP (DCA) Package With PowerPAD according to RθJA as specified in Section 4.4.

TPS65381A-Q1 power_dissipation_slvsbc4.gif
In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TAmax) is dependent on the maximum-operating junction temperature (TJmax), the maximum power dissipation of the device in the application (PDmax), and the junction-to-ambient thermal resistance of the part/package in the application (RθJA), as given by the following equation: TAmax = TJmax – (RθJA × PDmax).
Maximum power dissipation is a function of TJmax, RθJA, and TA. The maximum-allowable power dissipation at any allowable ambient temperature is PD = (TJmax – TA) / RθJA.
Figure 8-3 Derating Profile for Power Dissipation Based on High-K JEDEC PCB

Considering the power dissipation of the device in the specific application is important, which is highly dependent on the supply voltage and load currents, the ambient and board temperatures, and any additional heat sink or cooling strategies necessary to maintain the junction temperature of the device below the maximum junction temperature of 150°C.


The VDD1 regulator may have significant power dissipation in the external FET depending on the VDD1 voltage and load current. The external FET power dissipation for the VDD1 regulator must be considered in system-level thermal analysis. If better efficiency or thermal performance is needed, a DC-DC regulator could be used instead of the linear regulator controller with external FET. The output voltage of the DC-DC regulator can still be monitored by the VDD1_SENSE pin similar to the VDD1 output voltage when the VDD1 linear regulator controller is used with an external FET.


The PowerPAD thermal pad is not directly connected to any leads of the package. However, it is electrically and thermally connected to the substrate, which is the ground (GND) and power ground (PGND) of the device.


Additional information about thermal analysis and design can be found on in the WEBENCH® Design Center thermal analysis section.