SLOS717B August   2011  – December 2014 TPA2025D1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Operating Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Battery Tracking Automatic Gain Control (AGC)
      2. 9.3.2 Boost Converter Auto Pass Through (APT)
      3. 9.3.3 Short Circuit Auto-Recovery
      4. 9.3.4 Thermal Protection
      5. 9.3.5 Operation with DACS and Codecs
    4. 9.4 Device Functional Modes
      1. 9.4.1 Operation Below AGC Threshold
      2. 9.4.2 Shutdown Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Boost Converter Component Section
          1. 10.2.2.1.1 Inductor Equations
          2. 10.2.2.1.2 Boost Converter Capacitor Selection
          3. 10.2.2.1.3 Boost Terms
        2. 10.2.2.2 Input Capacitors
        3. 10.2.2.3 Speaker Load Limitation
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 Power Supply Decoupling Capacitors
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Trademarks
    2. 13.2 Electrostatic Discharge Caution
    3. 13.3 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

10.1 Application Information

The TPA2025D1 is a Class D amplifier with integrated automatic gain control and boost converter. This device is capable of drive up to 1.9W to 8-Ω Speaker (1% THD+N). TPA2025D1 starts operating when setting EN pin to HIGH level. The device enters in shutdown mode when asserting EN to LOW level. AGC pin connection sets the threshold where the device will start reducing the output amplitude. The selectable threshold voltages are specified in the Operating Characteristics section. In order to measure the TPA2025D1 output with an analyzer, a 30KHz Low pass filter should be implemented.

10.2 Typical Application

Graph_Test_Measurment_Setup_los717.png
1. The 1-µF input capacitors on IN+ and IN- were shorted for input common-mode voltage measurements.
2. A 33-µH inductor was placed in series with the load resistor to emulate a small speaker for efficiency measurements.
3. The 30-kHz low-pass filter is required even if the analyzer has an internal low-pass filter. An R-C low-pass filter (100 Ω, 47 nF) is used on each output for the data sheet graphs.
Figure 25. Typical Application Schematic

10.2.1 Design Requirements

For this design example, use the parameters listed in Table 1.

Table 1. Design Parameters

PARAMETER VALUE
Supply voltage range 2.5 V - 5.2 V
Input voltage range 0 V - 5 V
Peak output voltage 5.45 V
Max output current 1.8 A

10.2.2 Detailed Design Procedure

10.2.2.1 Boost Converter Component Section

The critical external components are summarized in the following table:

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Boost converter inductor At 30% rated DC bias current of the inductor 1.5 2.2 4.7 µH
Boost converter input capacitor 4.7 10 µF
Boost converter output capacitor Working capacitance biased at boost output voltage, if 4.7µH inductor is chosen, then minimum capacitance is 10 µF 4.7 22 µF

10.2.2.1.1 Inductor Equations

Inductor current rating is determined by the requirements of the load. The inductance is determined by two factors: the minimum value required for stability and the maximum ripple current permitted in the application. Use Equation 1 to determine the required current rating. Equation 1 shows the approximate relationship between the average inductor current, IL, to the load current, load voltage, and input voltage (IPVDD, PVDD, and VBAT, respectively). Insert IPVDD, PVDD, and VBAT into Equation 1 and solve for IL. The inductor must maintain at least 90% of its initial inductance value at this current.

Equation 1. EQ1_IL_los638.gif

Ripple current, ΔIL, is peak-to-peak variation in inductor current. Smaller ripple current reduces core losses in the inductor and reduces the potential for EMI. Use Equation 2 to determine the value of the inductor, L. Equation 2 shows the relationship between inductance L, VBAT, PVDD, the switching frequency, fBOOST, and ΔIL. Insert the maximum acceptable ripple current into Equation 2 and solve for L.

Equation 2. EQ2_L_los638.gif

ΔIL is inversely proportional to L. Minimize ΔIL as much as is necessary for a specific application. Increase the inductance to reduce the ripple current. Do not use greater than 4.7 μH, as this prevents the boost converter from responding to fast output current changes properly. If using above 3.3 µH, then use at least 10 µF capacitance on PVDD to ensure boost converter stability.

The typical inductor value range for the TPA2025D1 is 2.2 μH to 3.3 µH. Select an inductor with less than 0.5 Ω dc resistance, DCR. Higher DCR reduces total efficiency due to an increase in voltage drop across the inductor.

Table 2. Sample Inductors

L
(µH)		 SUPPLIER COMPONENT CODE SIZE
(LxWxH mm)		 DCR TYP
(mΩ)		 ISAT MAX
(A)		 C RANGE
2.2 Toko 1239AS-H-2R2N=P2 2.5 x 2.0 x 1.2 96 2.3 4.7 - 22 µF / 16 V
6.8 - 22 µV / 10 V
2.2 Coilcraft XFL4020-222MEC 4.0 x 4.0 x 2.15 22 3.5
3.3 Toko 1239AS-H-3R3N=P2 2.5 x 2.0 x 1.2 160 2.0 10 - 22 µF / 10 V
3.3 Coilcraft XFL4020-332MEC 4.0 x 4.0 x 2.15 35 2.8

10.2.2.1.2 Boost Converter Capacitor Selection

The value of the boost capacitor is determined by the minimum value of working capacitance required for stability and the maximum voltage ripple allowed on PVDD in the application. Working capacitance refers to the available capacitance after derating the capacitor value for DC bias, temperature, and aging. Do not use any component with a working capacitance less than 4.7 µF. This corresponds to a 4.7 μF/16 V capacitor, or a 6.8 μF/10 V capacitor.

Do not use above 22 μF capacitance as it will reduce the boost converter response time to large output current transients.

Equation 3 shows the relationship between the boost capacitance, C, to load current, load voltage, ripple voltage, input voltage, and switching frequency (IPVDD, PVDD, ΔV, VBAT, and fBOOST respectively).

Insert the maximum allowed ripple voltage into Equation 3 and solve for C. The 1.5 multiplier accounts for capacitance loss due to applied dc voltage and temperature for X5R and X7R ceramic capacitors.

Equation 3. EQ3_C_los638.gif

10.2.2.1.3 Boost Terms

The following is a list of terms and definitions used in the boost equations.

C Minimum boost capacitance required for a given ripple voltage on PVDD.
L Boost inductor
fBOOST Switching frequency of the boost converter.
IPVDD Current pulled by the Class-D amplifier from the boost converter.
IL Average current through the boost inductor.
PVDD Supply voltage for the Class-D amplifier. (Voltage generated by the boost converter output)
VBAT Supply voltage to the IC.
ΔIL Ripple current through the inductor.
ΔV Ripple voltage on PVDD.

10.2.2.2 Input Capacitors

Input audio DC decoupling capacitors are recommended. The input audio DC decoupling capacitors prevents the AGC from changing the gain due to audio DAC output offset. The input capacitors and TPA2025D1 input impedance form a high-pass filter with the corner frequency, fC, determined in Equation 4.

Any mismatch in capacitance between the two inputs will cause a mismatch in the corner frequencies. Severe mismatch may also cause turn-on pop noise. Choose capacitors with a tolerance of ±10% or better.

Equation 4. EQ_fc_los638.gif

10.2.2.3 Speaker Load Limitation

Speakers are non-linear loads with varying impedance (magnitude and phase) over the audio frequency. A portion of speaker load current can flow back into the boost converter output via the Class-D output H-bridge high-side device. This is dependent on the speaker's phase change over frequency, and the audio signal amplitude and frequency content. Most portable speakers have limited phase change at the resonant frequency, typically no more than 40 or 50 degrees. To avoid excess flow-back current, use speakers with limited phase change. Otherwise, flow-back current could drive the PVDD voltage above the absolute maximum recommended operational voltage.

Confirm proper operation by connecting the speaker to the TPA2025D1 and driving it at maximum output swing. Observe the PVDD voltage with an oscilloscope. In the unlikely event the PVDD voltage exceeds 6.5 V, add a 6.8 V Zener diode between PVDD and ground to ensure the TPA2025D1 operates properly. The amplifier has thermal overload protection and deactivates if the die temperature exceeds 150°C. It automatically reactivates once die temperature returns below 150°C. Built-in output over-current protection deactivates the amplifier if the speaker load becomes short-circuited. The amplifier automatically restarts 1.6 seconds after the over-current event. Although the TPA2025D1 Class-D output can withstand a short between OUT+ and OUT-, do not connect either output directly to GND, VDD, or VBAT as this could damage the device.

10.2.3 Application Curve

Fig22_Input_Impedance_vs_Gain_los717.pngFigure 26. Input Impedance vs Gain
Fig24_A-Weighted_Noise_vs_Frequency_8ohms_los717.pngFigure 28. A-Weighted Noise vs Frequency
Fig26_Shutdown_Timing_8ohms_los717.pngFigure 30. Shutdown Timing
Fig23_Boost_Startup_Current_vs_Time_4ohms_los717.pngFigure 27. Boost Startup Current vs Time
Fig25_Startup_Timing_8ohms_los717.pngFigure 29. Startup Timing
Radiated_Emissions_los717.pngFigure 31. EMC Performance Po = 750 mW with 2 Inch Speaker Cable