The **WM9090ECSS/R** is a high-performance, low-power audio subsystem designed by Wolfson Microelectronics (now part of Cirrus Logic). It is primarily used in mobile handsets and portable devices to drive high-fidelity audio while maintaining energy efficiency. --- ## 1. Core Technical Specifications The device integrates a digital-to-analog converter (DAC) with specialized speaker and headphone amplifiers. | Feature | Specification | | :--- | :--- | | **DAC Resolution** | 24-bit | | **Sampling Rate** | 8kHz to 48kHz | | **Speaker Amp** | 2.5W Class D into 4$\Omega$ (at 5V) | | **Headphone Amp** | Class W (Ground-referenced) | | **Signal-to-Noise (SNR)** | 100dB (DAC to Headphone) | | **Interface** | I2C (Control), I2S/PCM (Data) | | **Package** | 20-ball WLCSP (Wafer Level Chip Scale Package) | --- ## 2. Key Electronic Components & Subsystems ### A. Class D Speaker Driver The chip features a mono Class D speaker amplifier. Unlike traditional Class A/B amps, the Class D stage uses pulse-width modulation (PWM) to achieve high efficiency (up to 90%), which preserves battery life and reduces heat dissipation in small mobile enclosures. ### B. Class W Headphone Amplifier The "Class W" architecture is a proprietary Wolfson technology. It uses an integrated **charge pump** to generate a negative supply rail. - **Benefit:** This allows the headphone output to be centered at 0V (ground-referenced). - **Electronic Impact:** It eliminates the need for large, expensive DC-blocking capacitors on the output, saving PCB space and improving low-frequency (bass) response. ### C. Digital Audio Interface (AIF) The device communicates with the Application Processor (AP) or Baseband via: - **Data:** I2S, Left Justified, or DSP modes. - **Control:** A 2-wire I2C serial interface used to configure registers (gain, EQ, power management). ### D. ReTune™ Mobile 5-Band Parametric EQ An integrated hardware-based equalizer allows for digital signal processing (DSP) to compensate for speaker housing limitations without taxing the main CPU. --- ## 3. Pinout Logic and Connectivity Since it is a **WLCSP** package, the connections are arranged in a ball grid array. Key pin groupings include: 1. **Power (AVDD, DCVDD, DBVDD):** Split power rails for analog, digital core, and I/O buffering. 2. **GND/AGND:** Separate grounds to minimize digital noise interference in the analog audio path. 3. **CP (Charge Pump):** Connection points for external reservoir capacitors required to generate the negative rail. 4. **Outputs:** SPKOUT+/- (Differential speaker) and HPOUTL/R (Headphone). --- ## 4. Part Number Breakdown * **WM9090:** Functional part series. * **ECS:** Package code (usually indicating WLCSP). * **R:** Tape and Reel packaging for automated SMT assembly.