SLUAA69 July   2020  – MONTH  TPS548D22

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 LED Driver Methods
    2. 1.2 Power Supply Solutions for Common-Cathode LED Display
  3. 2Principle of Synchronous Buck with Sinking Current Application
  4. 3 Design Considerations and Analysis
    1. 3.1 Choose an IC with Sufficient Current Sinking
    2. 3.2 Choose IC Supporting Negative OCP
    3. 3.3 Choose an IC Supporting Pre-Bias Startup
    4. 3.4 Analysis of System Startup
  5. 4 TI Devices and Functionalities
    1. 4.1 Negative OCP Functionality
    2. 4.2 Hiccup Mode and Latch-off Mode
    3. 4.3 UVP and OVP Functionality
  6. 5 TI Solution
  7. 6 Bench Test and Result
    1. 6.1 Bench Test Configuration
    2. 6.2 Startup Waveforms and Behaviors Analysis Overview
    3. 6.3 Startup Waveforms and Behaviors Analysis at the First OVP
    4. 6.4 Startup Waveforms and Behaviors Analysis after the First OVP
    5. 6.5 Waveforms and Behaviors Analysis of Startup Solution with Lazy Loading
  8. 7 Conclusion
  9. 8References

4 TI Devices and Functionalities

The power level of an LED display module varies from 100 W to 300 W by different pixel pitches. The common power levels for small pixel pitch LED signage in the market are 110 W, 150 W and 220 W. Design parameters and recommended devices are listed in Table 4-1 based on different power levels.

TPS548B22 and TPS548D22 are pin-to-pin, 25 A and 40 A, synchronous buck converter devices. TPS549B22 and TPS549D22 are the same series devices with an additional PMBus™ function for programming. For powering an LED display, the output voltage can be set or dynamically adjusted through PMBus™ to further optimize the design by adjusting the cathode voltage to more precisely match the red LED forward voltage. Since a voltage drop on the path varies in current (as determined by brightness), the red LED forward voltage may drop or increase if a fixed output voltage is applied.

Table 4-1 Design Parameters and Recommended Devices

Design Parameters

Specifications

110 W

150 W

220 W

Input Voltage

4.2 V

4.2 V

4.2 V

Output Voltage

1 V

1 V

1 V

Red LED Forward Voltage

3.2 V

3.2 V

3.2 V

Red LED Total Load Current

15 A

20 A

30 A

Blue and Green LED Forward Voltage

4.2 V

4.2 V

4.2 V

Blue and Green Total Load Current

15 A

20 A

30 A

Recommended Device

TPS548B22

TPS548B22

TPS548D22

Recommended Device With PMBus™

TPS549B22

TPS549B22

TPS549D22

This series of devices support soft-start, pre-bias start up, UVLO protection with external adjustment by precise enable hysteresis, and fault protection (OVP, UVP, OCP, OTP). In addition, hiccup mode or latch-off mode can be chosen by external resistor setting. The next sections will discuss some key functionality with TPS548D22. For more details, refer to the TPS548D22 1.5-V to 16-V VIN, 4.5-V to 22-V VDD, 40-A SWIFT™ Synchronous Step-Down Converter with Full Differential Sense Data Sheet.