Texas Instruments manual TPA005D12 Class-D EVM Performance Characteristics

TPA005D12 Class-D EVM Performance Characteristics

3.6 TPA005D12 Class-D EVM Performance Characteristics

The TPA005D12 class-D stereo audio power amplifier EVM was tested using an Audio Precision System II, model 2322, a 5-V regulated dc power supply, and the TI PNP audio power amplifier evaluation platform set up as described in Chapter 2. Results were obtained with 4-Ωand 8-Ωspeaker loads. The results are shown in Figures 3±11 through 3±17.

The frequency response shown in Figure 3±17 is a relatively flat 20 dB over the 20 Hz to 100 kHz frequency range. The lower and upper frequency corners can be adjusted to extend the frequency response.

Figure 3±11. Class-D Amplifier Frequency Response at 4 Ω

VOLTAGE AMPLIFICATION

			vs
	22.5		FREQUENCY
	20
dB	17.5
	15
±
Amplification	12.5
	10
	7.5
Voltage	5
	2.5
	0	VDD = 5 V
	±2.5	RL = 4 Ω
		TA = 25° C
	±5
	10	100	1k	10k	100k
			f ± Frequency ± Hz

Total harmonic distortion plus noise (THD+N) versus output power and frequency is shown in Figures 3±12 through 3±15 below. Figures 3±12 and 3±13 show power sweeps at a fixed frequency of 1 kHz. Switching and input noise begins to dominate at low power, while the distortion at the mid to upper power levels is a function of the class-D amplifier and the inductor. The lower frequency noise may be improved by either increasing the order of the filter or by increasing the amplifier switching frequency, which will further attenuate the switching noise in the audio band.

Midrange distortion is a combination of the switching noise of the output power transistors in the IC and the magnetic field created by the inductors. This distortion is minimized by good separation of the output filter inductors for each channel and through good EMI-reduction layout techniques.

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