The best audio quality for music playback in a cell phone, portable audio player, tablet, or other mobile device comes with a class AB linear amplifier. The downside is that the power efficiency is low and battery drain is high. Class D switching amplifiers will give you the ultimate power efficiency, but their electromagnetic interference (EMI) is usually too much for a portable device. So the usual solution is a compromised class AB solution.

The TLV320DAC3202 class G amplifier from Texas Instruments solves this problem. A class G amplifier is a class AB linear amplifier that has a switched dc supply that increases the overall efficiency at different signal power levels. The efficiency of a class AB amplifier is given by:

Efficiency = P_Load/P_VDD = π/4(V_P/V_DD)

V_DD is the supply voltage, and V_P is the peak value of a sine load voltage. The efficiency is best when V_P is close to V_DD. The maximum efficiency of 78.5% is achieved when V_P is equal to V_DD, but that’s hard to achieve at low signal levels. Class G provides two supply voltage levels that can be switched between ±V_DD and ±V_DD/2 (Fig. 1). The TLV320DAC3202 automatically selects the supply level that provides the best efficiency based on signal level.

The TLV320DAC3202 is a high-fidelity and low-power headphone amplifier with integrated digital-to-analog converter (DAC) and power rails. Its small size and high efficiency maximize battery life and performance. The digital audio interface supports industry-standard formats such as I²S and pulse code modulation, or PCM (Fig. 2).

Features such as volume setting, data width, and sampling rate are configurable for optimum flexibility and efficiency. The headset power control automatically adjusts the rail voltage based on the input signal to maximize efficiency and performance. The control interface uses an industry-standard I²C controller for ease of operation and reduction in device pin count. This stereo chip also includes:

• Ground-referenced click- and pop-free class G stereo headset driver
• 100-dB(A) channel signal-to-noise ratio (SNR) with 6.5 mW of quiescent power dissipation
• Built-in short-circuit protection for preventing supply rails overload
• Two sigma-delta DACs with 24-bit resolution
• I²C Interface for digital control
• 32-step volume control from 4 to –59 dB
• Internal clock derived from I²S bus clock
• 20-pin wafer chip-scale package, 0.5-mm pitch, 2 by 2.5 mm
• Direct battery and I/O supply, on-chip charge pumps for supply voltages ±V_DD = 1.8 V and ±V_DD/2 + 0.9 V derived from 1.8-V dc input

Furthermore, the chip can drive 1 VRMS at the headset driver output, per channel, in phase. It supports 16-, 20-, 24-, and 32-bit data widths and 8-, 11.025-, 12-, 16-, 24-, 32-, 44.1-, and 48-kHz sample rates. Also, it supports standard I²S, PCM, and left and right justified formats as well as data mixing with gain options.  

The TLV320DAC3202 is available now for $1.75 in 1000-unit quantities. Evaluation kits are available.

Texas Instruments
www.ti.com/tlv320dac3202-pr