The CS42L55 is a highly integrated, 24-bit, ultra-low power stereo CODEC featuring a very efficient ground centered Class H stereo headphone amplifier with low EMI performance.

The ADC input path allows independent channel control of a variety of features. The Programmable Gain Amplifier (PGA) provides analog gain with zero cross transitions. The ADC path includes a digital volume attenuator with soft ramp transitions and a programmable Automatic Level Control and noise gate to monitor the input signals and adjust the volume appropriately. An analog passthrough also exists, accommodating a lower noise, lower power analog in to analog out path to the headphone and line amplifiers, bypassing the ADC and DAC.

The DAC output path includes a fixed-function digital signal processing engine. Tone control provides bass and treble adjustment at four selectable corner frequencies. The digital mixer provides independent volume control for both the ADC output and PCM input signal paths, as well as a master volume control. Digital volume controls may be configured to change on soft ramp transitions while the analog controls can be configured to occur on every zero crossing. The DAC path also includes de-emphasis, limiting functions and a beep generator delivering tones selectable across a range of two full octaves.

The Class H stereo headphone amplifier combines the efficiency of an integrated step-down and inverting charge pump with the linearity of a Class AB amplifier. A step-down/inverting charge pump operates in two modes: +/-VCP mode or +/-(VCP/2) mode. Based on the amplifier’s output signal, internal logic automatically adjusts the output of the charge pump, +VHPFILT and –VHPFILT, to optimize efficiency. With these features, the amplifier delivers a ground-centered output with a large signal swing even at low voltages and eliminates the need for external DC-blocking capacitors.

These features make the CS42L55 the ideal solution for high end portable audio applications which require extremely low power consumption in a minimal amount of space. The CS42L55 is available in a 36-pin QFN package for the Commercial (-40 to +85° C) grade.