A low-noise always-on interference-robust 125kHz key fob wake-up receiver

One component in an automotive passive keyless entry (PKE) system is the always-on wake-up receiver in the key fob that typically operates at around 125 kHz. Low current consumption is crucial to achieve a coin cell battery lifetime of two years minimum. This paper describes a receiver that uses an N-path filtering amplifier chain to deal with new interfering challenges, such as wireless electrical vehicle charging (WEVC) stations, yielding a 61 dB suppression of an 85 kHz interferer. Stacking of dynamic threshold devices (dt-mos) in the input amplifier is used to reach a sensitivity of $45 \mu \mathrm{Vpp}$ at a total battery current consumption of $5.5 \mu \mathrm{~A}$.