3D capacitive transmission of analog signals with automatic compensation of the voltage attenuation

An architecture to compensate the voltage attenuation introduced by 3D capacitive coupling is proposed. The scheme is applied to the design of a prototype aimed at demonstrating that 3D technology based on capacitive coupling allows to transmit analog signals as well as digital ones. The scheme is based on a calibration channel which sets the gain of the variable gain amplifiers of signal channels in order to compensate for the voltage attenuation. The prototype is designed in CMOS 90 nm technology. 3D assembling is done at die level using a face to face stacking procedure. Each channel has an area 90x30 µm2 and a power consumption of 1 mW. A gain error within 10% with respect to the nominal value has been measured for a signal amplitude varying from 200 mV to 1 V in the 100 KHz to 20 MHz range.