This article presents a wireless multi-channel sensor
interface circuit for emerging e-skin applications. The proposed
interface circuit uses a CDMA-like sensing method to simultaneously
record 16-channel resistive sensors and 16-channel
capacitive sensors. The code-modulated multi-channel signals are
conditioned and wirelessly transmitted through an edge-encoded
pulsewidth-modulation ultra-wideband (PWM UWB) transmitter
in the time domain. The PWM UWB transmitter eliminates
the need for digitization on the sensor node, reducing the
number of data to be sent. This improves the sensing and
wireless transmission efficiency.With the proposed edge-encoding
technique, the PWM UWB transmitter can recover the sensor
data with SNR above 70 dB despite 20% data loss under a
lossy environment. Fabricated in 130-nm technology, the wireless
multi-channel sensor node occupies a die area of 1.35 mm2 and
consumes a power of 70 μW. It achieves an energy efficiency
of 0.87 pJ/Conversion-step per channel.