SLOA326 October   2022 TAS2781

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Hybrid-Pro Boost Controller
  5. 3Hardware, Software, and Test Results
    1. 3.1 Hardware Connections
      1. 3.1.1 Schematic Connections
      2. 3.1.2 Equations
    2. 3.2 Software Settings
      1. 3.2.1 Steps To Enable Class-H Using PPC3
      2. 3.2.2 Class-H Configuration Settings
    3. 3.3 Hybrid-Pro Feature Performance Results
      1. 3.3.1 Class-H Operation
        1. 3.3.1.1 PWM Steps
        2. 3.3.1.2 Lookahead Time
        3. 3.3.1.3 Margin
        4. 3.3.1.4 Inflation Factor
      2. 3.3.2 Battery Life
      3. 3.3.3 Thermal Performance
  6. 4References

2 Hybrid-Pro Boost Controller

The TAS2781 and TAS2783 (hereafter termed TAS278x when interchangeable in this application note) have an internal Hybrid-Pro algorithm allowing users to optimize the efficiency in the system by controlling the external power supply with just enough margin to provide high dynamic range with low distortion.

Features of Hybrid-Pro control:

  • Hybrid-Pro control waveform is configurable as either 8 or 16 output voltage steps with 384-kHz or 192-kHz PWM, respectively, for external boost converter
  • Configurable maximum 4-ms look-ahead audio signal delay for various bandwidth and load capacitance combinations of external boost converters in the system
  • Low distortion output with optimum programmable peak hold time up to 8 ms
  • Balances efficiency with envelope tracking by dynamically adjusting the audio signal trigger level and the output voltage step size of the external boost converter

The Hybrid-Pro boost controller generates a PWM signal at the PWM_CTRL pin with a duty cycle proportional to the peak voltage at the speaker. The signal is converted to an analog voltage to control boost converter feedback (FB) input using an external low-pass filter as shown in Figure 2-1 (see Section 3.1 for details).

Figure 2-1 TAS2781 or TAS2783 Device Interface With Boost

By default, the PWM_CTRL pin is configured in an open drain. This configuration allows an easy implementation of a multichannel control loop using a common low-pass filter (LPF). Multiple TAS278x devices can be connected to the same LPF. One pullup resistor is needed between the common connection of the pins and IOVDD rail (see Figure 2-2).

Figure 2-2 Multichannel Configuration Using PWM_CTRL Pin With Open Drain

When only one amplifier is driving the LPF, program the PWM_CTRL pin as a push-pull driver. This helps to improve efficiency and reduce one of the external components.