Diodes Incorporated PAM8408DR

Overview

PAM8408DR from Diodes Incorporated is a 2×3W stereo filter-less Class-D audio amplifier with differential inputs, 32-step memory volume control (−80 dB to +24 dB), 87% peak efficiency at 5 V/4 Ω, and integrated short-circuit and thermal protection. It operates from 2.5 V to 6.0 V and targets portable battery-powered speakers requiring low-EMI, low-pop-noise, and minimal external components.

For engineers reviewing the PAM8408DR datasheet, PAM8408DR pinout, PAM8408DR application, or PAM8408DR equivalent, key selection considerations include its SO-16L package footprint, differential input architecture for noise rejection, shutdown-controlled gain retention, and compatibility with alkaline (up to 4-cell) or Li-ion power rails.

Technical Context

The PAM8408DR implements a two-stage internal amplifier architecture: a programmable-gain first stage (externally set via R_f/R_i) followed by a fixed 2× inverting second stage, yielding a maximum differential gain of 24 dB. Its oscillator runs at 250 kHz ±20%, driving a 30 Hz volume control clock derived via 2¹³ division.

It uses fully differential analog inputs per channel (RINP/RINN, LINP/LINN), supports logic-level UP/DOWN volume toggling with adaptive timing (1-cycle initial step, then 10-cycle → 4-cycle ramp), and features undervoltage lockout (UVLO) at 2.4 V with automatic recovery. Shutdown (SD) disables bias circuitry while preserving gain setting.

Key Specifications

Pinout & Package

Package: SO-16L (10.0 × 4.0 mm, 1.26 mm height, Pb-free, RoHS-compliant).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stereo Class-D audio amplifier applications.

Compared with PAM8408DR, PAM8019E offers enhanced efficiency and qualification readiness but requires minor layout updates; TPA2013D1 trades differential input and ultra-low IQ for digital control flexibility and broader voltage tolerance at higher static power.

Availability

PAM8408DR is available at Aetrix Electronics and suitable for PC speakers, wireless speakers, and active speaker systems requiring stable component supply despite its obsolete status-inventory is managed for legacy design support and repair fulfillment.

Supply support for PAM8408DR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-efficiency power management, signal integrity, and audio solutions for consumer, industrial, and computing markets.

The PAM8408DR belongs to Diodes' Class-D audio amplifier product line, engineered specifically for space- and power-constrained portable audio applications requiring low-EMI, low-pop-noise, and battery-friendly operation.

FAQ

What is the recommended input capacitor value for PAM8408DR?

Diodes recommends a 0.1 µF ceramic input capacitor per channel to balance low-frequency response (≥100 Hz corner), PCB area, and turn-on pop suppression. Larger values increase pop risk due to slow DC bias settling; smaller values may attenuate bass content below 150 Hz, which aligns with typical portable speaker capabilities.

Does PAM8408DR require an output LC filter?

No. The PAM8408DR uses filter-less Class-D modulation, enabling direct connection to 4 Ω or 8 Ω speakers without external inductors or capacitors. This reduces BOM cost, PCB area, and EMI concerns-though ferrite beads (e.g., 600 Ω @ 100 MHz) on output traces are advised for compliance in noisy environments.

How does the UP/DOWN volume control retain settings during shutdown?

The PAM8408DR stores the current gain step in nonvolatile analog state; applying logic low to SD pin powers down bias circuitry but preserves the 32-step volume register. Upon wake-up, the amplifier resumes at the exact same dB level-no MCU intervention or EEPROM backup is needed.

What thermal derating applies above 25°C ambient?

With θ_JA = 40 °C/W, the PAM8408DR's junction temperature rises ~40°C per watt dissipated. At 85°C ambient and 2.4 W output (1.7 W dissipation), junction temp reaches ~153°C-exceeding the 150°C limit. Derate output power linearly above 25°C; at 60°C ambient, max safe output drops to ~1.8 W into 4 Ω.