SLVSKU8 July   2026 TPS55285A

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 I2C Timing Requirements
    7. 5.7 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  VCC Power Supply
      2. 6.3.2  Default Output Enable (OE) Bit Status
      3. 6.3.3  Input Undervoltage Lockout
      4. 6.3.4  Enable and Programmable UVLO
      5. 6.3.5  Soft Start
      6. 6.3.6  Shutdown and Load Discharge
      7. 6.3.7  Switching Frequency
      8. 6.3.8  Switching Frequency Dithering
      9. 6.3.9  Inductor Current Limit
      10. 6.3.10 Internal Charge Path
      11. 6.3.11 Output Voltage Setting
      12. 6.3.12 Output Current Limit
      13. 6.3.13 Output Cable Voltage Drop Compensation
      14. 6.3.14 Input Overvoltage Protection
      15. 6.3.15 Output Overvoltage Protection
      16. 6.3.16 Output Short-Circuit Protection
      17. 6.3.17 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 PWM Mode
      2. 6.4.2 Power Save Mode
    5. 6.5 Programming
      1. 6.5.1 Data Validity
      2. 6.5.2 START and STOP Conditions
      3. 6.5.3 Byte Format
      4. 6.5.4 Acknowledge (ACK) and Not Acknowledge (NACK)
      5. 6.5.5 Target Address and Data Direction Bit
      6. 6.5.6 Single Read and Write
      7. 6.5.7 Multi-Read and Multi-Write
  8. 7 Register Maps
    1. 7.1 REF Register (Address = 0h, 1h) [reset = 10100100b, 00000001b]
    2. 7.2 IOUT_LIMIT Register (Address = 2h) [reset = 11100100b]
    3. 7.3 VOUT_SR Register (Address = 3h) [reset = 00000001b]
    4. 7.4 VOUT_FS Register (Address = 4h) [reset = 00000011b]
    5. 7.5 CDC Register (Address = 5h) [reset = 11110000b]
    6. 7.6 MODE Register (Address = 6h) [reset = 00100000b]
    7. 7.7 STATUS Register (Address = 7h) [reset = 00000001b]
    8. 7.8 Register Summary
  9. 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 Switching Frequency
        2. 8.2.2.2 Output Voltage Setting
        3. 8.2.2.3 Inductor Selection
        4. 8.2.2.4 Input Capacitor
        5. 8.2.2.5 Output Capacitor
        6. 8.2.2.6 Output Current Limit
        7. 8.2.2.7 Loop Stability
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

6.3.11 Output Voltage Setting

There are two ways to set the output voltage: changing the feedback ratio and changing the reference voltage. The TPS55285A has a 11-bit DAC to program the reference voltage from 45mV to 1.2V. The TPS55285A selects an internal feedback resistor divider or an external resistor divider by setting the FB bit in register 04h. When the FB bit is set to 0, the output voltage feedback ratio is set in internal register 04h. When the FB bit is set to 1, the output voltage feedback ratio is set by an external resistor divider.

When using internal output voltage feedback settings, there are four feedback ratios programmable by writing the INTFB[1:0] bits of register 04H. With this function, the TPS55285A limits the maximum output voltage to different values. In addition, the minimum step of the output voltage change is also programmed to 10mV, 7.5mV, 5mV, and 2.5mV, accordingly.

When using an external output voltage feedback resistor divider as shown in Figure 6-4, use Equation 3 to calculate the output voltage with the reference voltage at the FB/INT pin.

Equation 3. TPS55285A
TPS55285A Output Voltage Setting by External Resistor DividerFigure 6-4 Output Voltage Setting by External Resistor Divider

TI recommends using 100kΩ for the up resistor RFB_UP. The reference voltage VREF at the FB/INT pin is programmable from 45mV to 1.2V by writing an 11-bit data into register 00H and 01H.