SLUSAE6B December   2010  – November 2023 TPS53315

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  D-CAP™ Integrated Circuit with Adaptive On-Time
      2. 6.3.2  Small Signal Model
      3. 6.3.3  Ramp Signal
      4. 6.3.4  Auto-Skip Eco-mode Light Load Operation
      5. 6.3.5  Adaptive Zero Crossing
      6. 6.3.6  Forced Continuous Conduction Mode
      7. 6.3.7  Power Good
      8. 6.3.8  Current Sense and Overcurrent Protection
      9. 6.3.9  Overvoltage and Undervoltage Protection
      10. 6.3.10 UVLO Protection
      11. 6.3.11 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Enable and Soft Start
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Typical Application Circuit Diagram
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Step 1: Select Operation Mode and Soft-Start Time
          2. 7.2.1.2.2 Step 2: Select Switching Frequency
          3. 7.2.1.2.3 Step 3: Select the Inductance
          4. 7.2.1.2.4 Step 4: Select Output Capacitors
          5. 7.2.1.2.5 Step 5: Determine the Voltage-Divider Resistance (R1 and R2)
          6. 7.2.1.2.6 Step 6: Select the Overcurrent Resistance (RTRIP)
        3. 7.2.1.3 Application Curves
      2. 7.2.2 Typical Application Circuit Diagram With Ceramic Output Capacitors
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
          1. 7.2.2.2.1 Step 1: Select Operation Mode and Soft-Start Time
          2. 7.2.2.2.2 Step 2: Select Switching Frequency
          3. 7.2.2.2.3 Step 3: Select the Inductance
          4. 7.2.2.2.4 Step 4: Select Output Capacitance for Ceramic Capacitors
          5. 7.2.2.2.5 Step 5: Select the Overcurrent Setting Resistance (RTRIP)
        3. 7.2.2.3 External Component Selection When Using All Ceramic Output Capacitors
        4. 7.2.2.4 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
        1. 7.4.2.1 Thermal Considerations
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

6.3.1 D-CAP™ Integrated Circuit with Adaptive On-Time

The TPS53315 does not have a dedicated oscillator to determine switching frequency. However, the device operates with pseudo-constant frequency by feed-forwarding the input and output voltages into the on-time one-shot timer. The adaptive on-time control adjusts the on-time to be inversely proportional to the input voltage and proportional to the output voltage GUID-D6042A82-266C-48FA-81D3-2817C5012896-low.gif.

This makes the switching frequency fairly constant in steady state conditions over a wide input voltage range. The switching frequency is selectable from eight preset values by a resistor connected between the RF pin and GND or between the RF pin and the VREG pin as shown in Table 6-1. Leaving the resistance open sets the switching frequency to 500 kHz.

Table 6-1 Resistor and Switching Frequency
RESISTOR (RRF) CONNECTIONSSWITCHING FREQUENCY (kHz)
0 Ω to GND250
187 kΩ to GND300
619 kΩ to GND400
Open500
866 kΩ to VREG600
309 kΩ to VREG750
124 kΩ to VREG850
0 Ω to VREG970

The off-time is modulated by a PWM comparator. The VFB node voltage (the mid-point of resistor divider) is compared to the internal 0.6-V reference voltage added with a ramp signal. When the signal values match, the PWM comparator asserts a set signal to terminate the off-time (turn off the low-side MOSFET and turn on high-side MOSFET). The set signal is valid if the inductor current level is below the OCP threshold, otherwise the off-time is extended until the current level falls below the threshold.

Figure 6-1 and Figure 6-2 show two on-time control schemes.

GUID-4D21EF78-C2A0-4C2C-8A86-D30B48183931-low.gifFigure 6-1 On-Time Control Without Ramp Compensation
GUID-5E41B88E-5407-4B92-994F-9C6253626BA8-low.gifFigure 6-2 On-Time Control With Ramp Compensation