The THAT626x series combines two low power, low noise microphone preamplifiers, with a programmable gain stage offering click-less switching plus an ADC driver. All this functionality is packed into a 7x7mm QFN package and consumes a mere 30mW per channel.
Audio performance is not compromised at all by the low power consumption, as the input noise is -127dBu (Ein) at max gain. There are three versions available, differing only on gain-step size and price; the options are 1dB, 3dB or 6dB gain steps.
The THAT626x chips accept +16.5dBu input signals and are designed to directly drive common ADCs to 2Vrms full-scale. The analogue gain range is -8dB to +34dB, which is scaled optimally for the ADCs. Additional gain can be added in the digital domain usually without loss of quality – amplifying the input noise by 34dB will typically increase the noise above the noise floor of the ADC, and so maximum signal to noise is already achieved.
The control stage features zero crossing detectors that can be synchronised with the external DSP to facilitate finer gain steps if required.
Evaluation boards and SPICE models are available to further speed up the design process.