Texas Instruments Audio ICs: Class-D Amplifiers & Haptics

A Texas Instruments audio amplifier is almost always a Class-D device — a switching output stage that hits 90 percent efficiency where a linear Class-AB amp manages 50 to 65 percent. TI’s audio, haptics and piezo line covers Class-D speaker amplifiers, audio codecs, haptic motor drivers and high-voltage piezo drivers. This guide breaks down the families with real part numbers and headline specs, then covers the EMI and layout work that decides whether the audio path is clean and the design passes emissions.

The reason to start with the category instead of a single part is that an audio sub-system is rarely one chip. A codec digitises and processes, a Class-D amp drives the speaker, a haptic driver runs the vibration motor, and all of it sits on a supply rail that has to stay quiet under load.

• Class-D audio amps: the TAS5825M delivers 38 W stereo or 65 W mono from 4.5 V to 26 V with an integrated DSP and 192-kHz processing.
• Class-H / Hybrid-Pro: the TAS5825P tracks the supply to the signal and extended battery runtime by more than 50 percent in TI’s tests.
• Haptics: the DRV2605L drives ERM and LRA actuators with auto-resonance and a licensed effect library over I²C.
• Filterless Class-D saves a filter but radiates EMI on long speaker cables — the trade-off is space versus emissions compliance.

What a TI Audio Amplifier Is and How the Families Break Down

A Class-D amplifier switches its output transistors fully on or off at a high carrier frequency and reconstructs the audio with the speaker’s inductance and a small filter. Because the transistors are never half-on, they dissipate little heat, which is why Class-D dominates battery and compact designs. TI builds three working groups: speaker amplifiers, audio codecs (combined ADC and DAC with processing), and actuator drivers for haptics and piezo elements.

Modern TI speaker amps are closed-loop and “smart.” The TAS5825M runs a DSP that handles equalisation, dynamic range control, an automatic gain limiter, and a smart-amp algorithm that models the speaker’s thermal and excursion limits so you can push more loudness from a small driver without destroying it. That last point is a quiet revolution: the chip protects the speaker, not just itself.

TI Class-D Audio Amplifier Selection: Power, Efficiency and Supply

Choose by output power, supply rail and how much you care about idle battery drain. The table compares representative TI parts.

TI audio part	Type	Key specs	Use it for
TAS5825M	Closed-loop Class-D + DSP	38 W stereo / 65 W mono, 4.5–26 V, 192 kHz	TVs, soundbars, smart speakers
TAS5825P	Class-H Hybrid-Pro	Tracks PVDD; >50% longer battery in TI tests	Battery speakers, portables
TAS5828M	Closed-loop Class-D	50 W stereo, integrated processor	Higher-power portable audio
TAC5112	Stereo audio codec	105 dB ADC / 114 dB DAC dynamic range	Capture-and-playback paths

A counterintuitive point about closed-loop Class-D: because it actively rejects supply ripple (high PSRR), you can often feed it from a cheaper, noisier DC-DC rail than a linear amp would tolerate. The amplifier cleans up its own supply. The flip side is that idle current and EMI behaviour, not peak watts, usually decide the design, so read the idle-power and emissions sections of the datasheet before the power rating.

The second non-obvious fact: bigger numbers do not mean sustained loudness. Thermal foldback and the smart-amp excursion model cap continuous output well below the peak watts on the front of the datasheet. Size the amplifier for the loudness you need continuously, not the headline burst figure.

TI Haptic and Piezo Drivers for Tactile Feedback

Tactile feedback needs a driver matched to the actuator. The DRV2605L runs eccentric-rotating-mass (ERM) and linear-resonant-actuator (LRA) motors with a smart-loop architecture that auto-tunes to the LRA’s resonant frequency and brakes it cleanly, plus a licensed library of over 100 effects addressable over I²C. It runs from 2 V to 5.2 V, so it suits wearables and handhelds. For piezo actuators that need high voltage, the DRV2700 integrates a 105 V boost switch and a differential amplifier and can swing piezo loads up to roughly 500 V in a flyback configuration.

These actuator drivers connect to the rest of the board through Texas Instruments power management ICs for the boost or supply rail, and the audio capture path uses Texas Instruments data converters or an integrated codec. For analog gain and buffering elsewhere in the chain, Texas Instruments amplifiers cover the precision and line-level stages.

Class-D Layout and EMI: Where Audio Designs Fail Compliance

The Class-D output is a fast-switching node, and that is where audio boards fail emissions testing. The recurring issues:

1. Long speaker traces on a filterless amp. Filterless (inductor-less) Class-D works only when the speaker is close. Run the output a long way — to an internal soundbar driver, for example — and the switching edges radiate. Add a ferrite-bead or LC output filter for those runs.
2. The exposed thermal pad. High-power Class-D parts dump heat through a bottom pad; stitch it with thermal vias and give it proper paste coverage, or thermal foldback robs you of output.
3. Supply decoupling and the PVDD loop. Bulk and ceramic decoupling close to the supply pins keeps the switching current local; a loose loop both radiates and modulates the audio.
4. Spacing on the PVDD rail per the IPC-2221 conductor guidance, and grading the assembled joints against IPC-A-610.

A soundbar client passed bench audio tests but failed radiated-emissions compliance. The cause was filterless Class-D outputs driving speakers through long internal cables that acted as antennas at the switching frequency. Adding small LC output filters at the amplifier brought the design under the CISPR limit with no audible change. The amplifier was fine; the cable was the radiator.

The TI Audio Sub-Families and Where Each Belongs

Beyond the headline Class-D amplifier, the audio, haptics and piezo category divides into clear sub-families, and matching the device to the role keeps the bill of materials lean. Speaker amplifiers split between smart-amp parts that protect the speaker (the TAS5825M, with its thermal and excursion model) and Class-H parts that chase battery efficiency (the TAS5825P, whose Hybrid-Pro algorithm tracks the supply to the signal). Audio codecs such as the TAC5112 combine a high-dynamic-range ADC and DAC — 105 dB and 114 dB respectively — for designs that both capture and play back.

Actuator drivers form the second half of the category. Haptic drivers like the DRV2605L run small vibration motors with a built-in effect library, while high-voltage piezo drivers like the DRV2700 generate the hundreds of volts that piezo elements and ceramic speakers need. The selection rule is simple: decide first whether you are moving air (a speaker), moving mass (a haptic motor), or driving a piezo element, then pick the matched driver.

• Drive a magnetic speaker — use a Class-D amplifier (TAS5825M for smart protection, TAS5825P for battery life).
• Add tactile feedback — use a haptic driver (DRV2605L) matched to your ERM or LRA actuator.
• Drive a piezo element or ceramic speaker — use a high-voltage piezo driver (DRV2700) for the high-voltage swing.

A practical configuration point that affects both loudness and layout is the output mode. A bridge-tied-load (BTL) connection drives the speaker differentially across two amplifier outputs and delivers roughly four times the power of a single-ended connection into the same load, which is why most TI Class-D amps are specified BTL. Mono operation often parallels the bridge (PBTL) for even higher current into a single low-impedance driver such as a subwoofer.

Common TI Audio Amplifier Mistakes

1. Specifying peak watts and ignoring the lower continuous output set by thermal foldback.
2. Running filterless Class-D outputs over long cables and then failing EMC.
3. Pairing a haptic driver to the wrong actuator type (ERM settings on an LRA, or vice versa).
4. Starving the exposed thermal pad of paste or thermal vias.
5. Treating the codec’s reference and analog ground as an afterthought, which adds noise to the capture path.

Frequently Asked Questions About TI Audio ICs

Why are most TI audio amplifiers Class-D?

Because Class-D switches its output devices fully on or off, it wastes little power as heat — efficiency around 90 percent versus roughly 50 to 65 percent for linear Class-AB. That efficiency means smaller heatsinks, longer battery life and more output from a compact package.

What is a smart amplifier?

A smart amplifier such as the TAS5825M adds a DSP that models the speaker’s thermal and mechanical (excursion) limits in real time, letting you drive more loudness from a small speaker safely. It also handles equalisation and dynamic range control on-chip.

Do I need an output filter on a TI Class-D amp?

Not if the speaker sits close to the amplifier — filterless operation is fine. For long speaker cables, add a ferrite-bead or LC filter at the output to control electromagnetic emissions and pass EMC testing.

What is the difference between ERM and LRA haptics?

An ERM (eccentric rotating mass) spins a weighted motor; an LRA (linear resonant actuator) vibrates at a fixed resonant frequency for sharper, faster feedback. The DRV2605L drives both and auto-tunes the LRA resonance for consistent performance.

How do I drive a piezo speaker or actuator with TI parts?

Use a high-voltage piezo driver such as the DRV2700, which integrates a 105 V boost and a differential amplifier and can reach roughly 500 V for high-voltage piezo loads, eliminating a discrete high-voltage supply.

How do I choose a TI audio codec versus a separate ADC and DAC?

A codec such as the TAC5112 integrates the capture and playback paths with matched performance and a single clock domain, simplifying layout and reducing board area. Discrete converters give more flexibility and higher peak performance when the record and playback requirements differ sharply, but for most voice and general audio paths the integrated codec is the cleaner choice.

What is the difference between BTL and single-ended output?

A bridge-tied load drives the speaker across two amplifier outputs differentially, delivering about four times the power of a single-ended output into the same impedance and cancelling some common-mode noise. Most TI Class-D amplifiers run BTL, with a paralleled (PBTL) mode for higher mono current into low-impedance drivers.

Build Your TI Audio Path Cleanly

Match the amplifier to your continuous loudness and supply, choose the right actuator driver, and treat the Class-D output and supply layout as an EMC problem from the start. Send your Gerber and BOM for a DFM review so the output filtering, thermal pad and decoupling are checked before the first build, and return to the Texas Instruments component hub to complete the design.