SLVSE55 November   2017 TPS65321A-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Buck Regulator
        1.  Fixed-Frequency PWM Control
        2.  Slope Compensation Output
        3.  Pulse-Skip Eco-mode™ Control Scheme
        4.  Dropout Mode Operation and Bootstrap Voltage (BOOT)
        5.  Error Amplifier
        6.  Voltage Reference
        7.  Adjusting the Output Voltage
        8.  Soft-Start Pin (SS)
        9.  Reset Output, nRST
        10. Overload-Recovery Circuit
        11. Constant Switching Frequency and Timing Resistor (RT/CLK Pin)
        12. Overcurrent Protection and Frequency Shift
        13. Selecting the Switching Frequency
        14. How to Interface to RT/CLK Pin
        15. Overvoltage Transient Protection
        16. Small-Signal Model for Loop Response
        17. Simple Small-Signal Model for Peak-Current Mode Control
        18. Small-Signal Model for Frequency Compensation
      2. 7.3.2 LDO Regulator
        1. Charge-Pump Operation
        2. Low-Voltage Tracking
        3. Adjusting the Output Voltage
      3. 7.3.3 Thermal Shutdown
      4. 7.3.4 Enable and Undervoltage Lockout
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 2-MHzSwitching Frequency, 9-V to 16-V Input, 3.3-V Output Buck Regulator, 5-V Output LDO Regulator
        1. Design Requirements
        2. Detailed Design Procedure
          1.  Switching Frequency Selection for the Buck Regulator
          2.  Output Inductor Selection for the Buck Regulator
          3.  Output Capacitor Selection for the Buck Regulator
          4.  Catch Diode Selection for the Buck Regulator
          5.  Input Capacitor Selection for the Buck Regulator
          6.  Soft-Start Capacitor Selection for the Buck Regulator
          7.  Bootstrap Capacitor Selection for the Buck Regulator
          8.  Output Voltage and Feedback Resistor Selection for the Buck Regulator
          9.  Frequency Compensation Selection for the Buck Regulator
          10. LDO Regulator
          11. Power Dissipation
            1. Power Dissipation Losses of the Buck Regulator
          12. Power Dissipation Losses of the LDO Regulator
          13. Total Device Power Dissipation Losses and Junction Temperature
        3. Application Curves
      2. 8.2.2 Design Example With 500-kHz Switching Frequency
        1. Design Requirements
        2. Detailed Design Procedure
          1. Selecting the Switching Frequency
          2. Output Inductor Selection
          3. Output Capacitor
          4. Compensation
        3. Application Curve
  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
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • PWP|14
Thermal pad, mechanical data (Package|Pins)
Orderable Information


  • Qualified for Automotive Applications
  • AEC-Q100 Qualified with the Following Results:
    • Device Temperature Grade 1: –40°C to +125°C Ambient Operating Temperature
    • Device HBM ESD Classification Level 2
    • Device CDM ESD Classification Level C4B
  • One High-VIN Step-Down DC-DC Converter
    • Input Range of 3.6 V to 36 V
    • 250-mΩ High-Side MOSFET
    • Maximum Load Current 3.2 A, Output Adjustable 1.1 V to 20 V
    • Adjustable Switching Frequency 100 kHz to 2.5 MHz
    • Synchronizes to External Clock
    • High Efficiency at Light Loads With Pulse-Skipping Eco-mode™ Control Scheme
    • Maximum 140-µA Operating Quiescent Current
    • Reset Output-Pin (Active Low, Open-Drain)
  • One High-VIN Low-Dropout (LDO) Voltage Regulator
    • Input Range of 3 V to 36 V
    • 280-mA Current Capability With Typical 35-µA Quiescent Current in No-Load Condition
    • Low-Dropout Voltage of 300 mV at
      IO = 200 mA (Typical)
  • Overcurrent Protection for Both Regulators
  • Overtemperature Protection
  • 14-Pin HTSSOP Package With PowerPAD™ Integrated Circuit Package


  • Automotive Infotainment and Cluster
  • Advanced Driver Assistance System (ADAS)
  • Automotive Telematics, eCall


The TPS65321A-Q1 device is a combination of a high-VIN DC-DC step-down converter, referred to as the buck regulator, with an adjustable switch-mode frequency from 100-kHz to 2.5-MHz, and a high-VIN 280-mA low-dropout (LDO) regulator. The input range is 3.6 V to 36 V for the buck regulator, and 3 V to
36 V for the LDO regulator. The buck regulator has an integrated high-side MOSFET with an active-low, open-drain power-good output-pin (nRST). The LDO regulator features a low-input supply current of 45-μA typical in no-load, also has an integrated MOSFET. Low-voltage tracking feature enables TPS65321A-Q1 to track the input supply during cold-crank conditions.

The buck regulator provides a flexible design to fit system needs. The external loop compensation circuit allows for optimization of the converter response for the appropriate operating conditions. A low-ripple pulse-skip mode reduces the no-load input-supply current to maximum 140 μA.

The device has built-in protection features such as soft start, current-limit, thermal sensing and shutdown due to excessive power dissipation. Furthermore, the device has an internal undervoltage-lockout (UVLO) function that turns off the device when the supply voltage is too low.

Device Information(1)

TPS65321A-Q1 HTSSOP (14) 5.00 mm × 4.40 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application Schematic

TPS65321A-Q1 alt_slvscf0.gif

Buck Efficiency Versus Output Current

TPS65321A-Q1 C001_slvscf0.gif