Texas Instruments APA100 manual 4.2 TPA2001D1 Class-DModulator

TPA2001D1 (Class-D Modulator)

Figure 4−6. PSPICE Simulation of Open−Loop Response

200

Phase (5)

100

−0

TAS5111

Output (dB)

−100

−200

−300

Integrator Output (dB)

100 1 k 10 k 100 k 1 M

f − Frequency − Hz

4.2 TPA2001D1 (Class-D Modulator)

The TPA2001D1 was chosen as an excellent performance, low-cost analog class-D modulator. A class-D modulator takes an analog input signal and outputs a pulse width modulated (PWM) signal. The TPA2001D1 was selected over other class-D amplifiers because of the following reasons.

1)Supply voltage range of 2.75 V to 5.5 V (matches up well with TAS5111 H-bridge).

2)Low noise (40 ∝V rms)

3)Low total harmonic distortion plus noise across 20 Hz to 20 kHz (<0.3% over 20-Hz to 20-kHz frequency range)

4)Low cost (~$0.75 each in 1 kU)

The TPA2001D1 takes an analog input signal, gains it up, and compares it to a 250-kHz triangle wave. The output of the comparator is a PWM signal. This PWM signal is processed to make a differential signal, and it is sent to the output MOSFETs. The TPA2001D1 outputs are capable of driving 1 W of output power, but they are only driving high impedance in this case (the TAS5111 inputs). The TPA2001D1 block diagram is shown in Figure 4−7.

Technical Information 4-7