Single chip audio power amplifier for electric vehicle warning sound system

Toshiba Electronics Europe (TEE) has developed a single-chip amplifier to support safety designs that add the sound of a conventional internal combustion engine to electric and hybrid electric vehicles (EVs and HEVs). The TB2909FNG is a compact and integrated power amplifier that also supports other external audible output including reversing alarms and ‘answerback’ confirmation for keyless remote entry security.

EVs and HEVs operating in all-electric mode are much quieter than vehicles driven by internal combustion engines. As a result, pedestrians, cyclists and other road users may be less aware of their presence – especially at low speeds. Because of this a number of manufacturers already equip their vehicles with an acoustic vehicle alerting system (AVAS). It is anticipated that such systems will become more prevalent as legislators seek to establish a minimum level and type of sound for low-speed, all-electric operation. Due to road users’ familiarity with traditional vehicles, a preferred sound is that of a normal vehicle engine.

Toshiba’s TB2909FNG power IC is a single-channel, Class-AB, single-ended push-pull (SEPP) amplifier specifically developed to amplify the simulated sound of a conventional engine. The device operates from a supply of between 6V and 16V and can deliver a maximum output power of 5W (Vcc = 16V, RL = 8O). Total harmonic distortion (THD) is rated at 0.08% (for an output power of 0.125W) and output noise voltage is just 50µV. Guaranteed operation between -40° and 110°C supports use in EV warning sound systems where stable performance at extended temperatures is required.

The new device is supplied in a TSSOP16 package with dimensions of just 4.4mm x 5.0mm x 1.0mm. Despite its compact size, the IC provides high levels of integrated functionality including a variety of mute capabilities and a built-in standby switch. Abnormality detection and protection for thermal overload, over-voltage, short circuits to GND or VCC, and speaker-open conditions are provided as standard, supporting functional safety.

Toshiba has developed the TB2909FNG using its BiCD-0.13 process. This process allows the integration of bipolar transistors, CMOS FETs and high-voltage DMOS elements on the same die.


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