MAX4397SACTM+

Audio Special Purpose: MAX4397SACTM+ Application Field and Working Principle

The MAX4397SACTM+ is a low-power, wideband, single-channel audio power amplifier IC intended for earphones, headsets and portable devices. It takes a single-ended input and provides a headphone output with range up to 300mW into 32 Ohm load.The device integrates a power amplifier and output resistors, thus requiring only two external capacitors for operation. The MAX4397SACTM+ can be powered-up from 1.7V to 5.5V and is capable of operating from a single supply. Due to the integrated output resistors, the output level is easily adjusted by changing the supply voltage.

MAX4397SACTM+ Application Field

The MAX4397SACTM+ represents a significant advance in earphone and headset output power compared to alternative solutions such as class AB amplifiers. This allows it to be used in a range of applications such as digital audio players, personal digital assistants (PDAs) and other digital media players requiring efficient audio power amplification.

Because of its wideband gain, the MAX4397SACTM+ gives identical power and performance over a range of frequencies including music and speech. This makes it ideal for sound reproduction requiring certain level of saturation, such as music on smartphones. The power amplifier has an integrated pop-noise suppression circuit, allowing it to be used without an external pop-noise suppressor.

MAX4397SACTM+ Working Principle

The MAX4397SACTM+ power amplifier comprises a power stage and an error amplifier, which is connected to a unity-gain output stage. The power stage comprises two high gain, fixed-gain power transistors connected in a Darlington circuit configuration. This Darlington pair provides high current gains and high output voltages. The two transistors are drivers of the power stage, and are driven by the error amplifier, whose output is adjusted by an internal voltage divider.

The output of the power amplifier is fully adjustable and can be set to the required level by changing the input bias and voltage divider resistors. The voltage divider is composed of an input resistor network, which decreases the voltage to an appropriate level. The error amplifier is then adjusted to maintain a certain output level. This prevents damage due to input overloads, such as clipping and distortion.

The two fixed-gain transistors are connected to a Darlington arrangement that ensures maximum current gain and power output. The power stage also comprises output resistors connected to the output to ensure that the output remains constant even with varying load impedances. The power amplifier is fully protected against thermal overload, DC offset and mute.

In summary, the MAX4397SACTM+ is an integrated, single-channel audio power amplifier IC intended for earphones, headsets and other portable applications. The IC integrates a power amplifier and output resistors, allowing it to be powered-up from 1.7V to 5.5V and provide headphone output up to 300mW. The power amplifier is optimized for wideband gain and features an integrated pop-noise suppression circuit, thus providing an efficient audio power amplification solution for portable devices.