1 Introduction
The audio Class D amplifier (CLASSD) implemented in Microchip microprocessors is a fully digital pulse-width-modulated (PWM) stereo output amplifier. It features a digitally-controlled attenuator for gain control, a 3-band equalizer and a de-emphasis filter.
On the input side, the CLASSD 16-bit digital input is compatible with the most common audio data rates: 8, 16, 32, 48 and 96 kHz (internally oversampled to 768 kHz), as well as 22.05, 44.1 and 88.2 kHz (internally oversampled to 705.6 kHz).
On the output side, the CLASSD PWM output can drive either:
- high-impedance single-ended or differential output loads (ΔΣ audio DAC applications) or
- external MOSFETs through an integrated non-overlapping circuit (power amplifier applications).
| Pin | External MOS Driver (NON_OVERLAP = 1) | Direct Load (NON_OVERLAP = 0) | Type | ||
|---|---|---|---|---|---|
| Full H-Bridge (PWMTYP = 1) | Half H-Bridge (PWMTYP = 0) | Differential Load (PWMTYP = 1) | Single-Ended Load
(PWMTYP = 0) | ||
| Use Case 1 | Use Case 2 | Use Cases 3A & 3B | Use Cases 4A & 4B | ||
| CLASSD_L0 | gate_pmos_leftp | gate_pmos_left | leftp | left | Output |
| CLASSD_L1 | gate_nmos_leftp | gate_nmos_left | Not used (fixed to 0) | Not used (fixed to 0) | Output |
| CLASSD_L2 | gate_pmos_leftn | Not used (fixed to 1) | leftn | Not used (fixed to 0) | Output |
| CLASSD_L3 | gate_nmos_leftn | Not used (fixed to 1) | Not used (fixed to 0) | Not used (fixed to 0) | Output |
| CLASSD_R0 | gate_pmos_rightp | gate_pmos_right | rightp | right | Output |
| CLASSD_R1 | gate_nmos_rightp | gate_nmos_right | Not used (fixed to 0) | Not used (fixed to 0) | Output |
| CLASSD_R2 | gate_pmos_rightn | Not used (fixed to 1) | rightn | Not used (fixed to 0) | Output |
| CLASSD_R3 | gate_nmos_rightn | Not used (fixed to 1) | Not used (fixed to 0) | Not used (fixed to 0) | Output |
Note: The microprocessor’s PIO controllers must be programmed first to
assign the CLASSD pins to their peripheral functions.