Consumer ICs
Volume 9, Issue 1 YOUR SEMICONDUCTOR SOLUTIONS RESOURCE

High Efficiency Class-D Amplifiers Enhance Portable Audio Applications

Class-D amplifiers are increasingly used to drive speakers efficiently in cellular phones, personal media players, laptop computers, and other handheld and portable consumer devices. ADI Class-D amplifiers employ spread spectrum pulse-density modulation to reduce electromagnetic interference (EMI), a filterless topology to eliminate external components, and an efficient architecture to minimize power consumption, making them ideal for portable applications. In addition, their lower power dissipation enables a more environmentally friendly solution.

ADI's low power Class-D audio product portfolio provides system designers with many options to allow them to select the right product for their system requirements. For example, the SSM2317 is a fully integrated, super high efficiency, Class-D audio amplifier with an auto level control (ALC) function built in. This function can be activated in order to suppress clipping and improve dynamic range. This is designed to maximize performance for mobile phone applications, as it requires only one external resistor tied to GND via the VTH pin and an activation voltage on the ALC_EN pin. The SSM2315 and the SSM2335 are industry-standard mono Class-D amplifiers that provide superb sound quality and the highest efficiency in the product category.

SSM2317

SSM2335 SSM2317 SSM2315

SSM2315 Features

  • Filterless Class-D amplifier with Σ-Δ modulation
  • Automatic level control (ALC)
  • Improves dynamic range
  • Prevents clipping: 93%
  • Efficiency at 5.0 V, 1.4 W into 8 Ω speaker
  • Signal-to-noise ratio (SNR): 93 dB

Robust and Adaptive Capacitive Switching for Ultralow Power Portable Products

In applications where power and space considerations are critical, the AD7156 is ideal for implementing single touch or proximity switching when only one or two capacitive sensors are required. The AD7156 is an ultralow power, 2-channel capacitance converter that delivers a complete signal processing solution for capacitive sensors. It has an ultralow current of 70 µA and a power supply extending from 3.6 V down to 1.8 V. It features two channels and is housed in a small, 3 mm × 3 mm × 0.8 mm, 10-lead LFCSP package.

The device is designed for ease of use and combines features important for interfacing to real-world sensors, such as high input sensitivity and high tolerance of both input parasitic ground capacitance and leakage current. The on-chip adaptive environmental compensation algorithm enables the device to adapt automatically to capacitance changes due to shifts in environmental conditions such as temperature, humidity, and the gradual buildup of dust and dirt. These features greatly ease the implementation of robust and highly sensitive capacitive sensor switches in the end product.

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AD7156

AD7156 Features

  • Operation power supply current: 70 µA typ
  • Package: 10-lead LFCSP (3 mm × 3 mm × 0.8 mm)
  • Fast conversion time: 10 ms per channel
  • Highest sensitivity
  • Adaptive environmental compensation
  • I2C-compatible interface
Part Number Channels Supply (V) Supply Current (µA) Conversion Time
Per Channel (ms)
Package Price ($U.S.)
AD7150 2 2.7 to 3.6 100 5 10-lead MSOP 1.37
AD7151 1 2.7 to 3.6 70 10 10-lead MSOP 1.37
AD7156 2 1.8 to 3.6 70 10 10-lead LFCSP 1.25

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