AS3542

The AS3542/3 is an ultra low power stereo audio codec and is designed for Portable Digital Audio Applications.

AS3542 allows high-end quality playback with up to 100dBA SNR and recording in FM quality. With one microphone (including pre-amplifier and supply for an electret microphone) and two line inputs, it allows connecting a variety of audio inputs. The different audio signals of AS3542 can be mixed via a 6-channel mixer and fed to either a headphone output for 16 /32 headsets or a line output. Both outputs have a ground noise cancellation to use AS3542 e.g. in car docking stations. The audio outputs have also an auto fading implemented which performs the fade-in, fadeout as well as the transition between specific volume levels automatically with an selectable timing.

Further AS3542 offers advanced power management functions. All necessary ICs and peripherals in a Digital Audio Player are supplied by the AS3542/3. It features 2 DCDC converters for core and memory/periphery supply as well as 4 LDOs. Both DCDC converter feature DVM (dynamic voltage management) with an selectable timing for the voltage stepping. The different regulated supply voltages are programmable via the serial control interface.

The step-up converter AS3542 for the backlight can operate up to 25V (with an external transistor even higher) in voltage and current control mode. An internal voltage protection is limiting the output voltage in the case of external component failures. 2 high voltage current sinks can be used to operate two , if needed also unbalanced, LED strings. An automatic dimming function allows a logarithmic on/off of the backlight with selectable timing. AS3542/3 also contains a Li-Ion battery charger with constant current, constant voltage and trickle charging. The maximum charging current is 460mA. An integrated battery switch is separating the battery during charging or whenever an external power supply is present. With this switch it is also possible to operate with no or deeply discharged
batteries.

The AS3542/3 has an on-chip, phase locked loop (PLL) which generates the needed internal CODEC master clock. I2S Frame and shift-clock have to be applied from the processor for playback and recording.

Further the AS3542/3 has an independent 32kHz real time clock (RTC) on chip which allows a complete power down of the system CPU while only consuming less than 1A. An internal switch automatically switches between the RTC backup-battery and main battery supply.

The single supply voltage may vary from 2.7V (2.4V) to 5.5V.