A 900-MHz high-sensitivity split-channel binary frequency-shift keying (SC-BFSK) reconfigurable data/wake-up receiver (RX) for low-power wide-area networks (LPWANs) is presented. In the data mode, the proposed RX demodulates data through the RF/analog front end (RXFE), the analog-to-digital converter (ADC), and the modulator-demodulator (MODEM). The MODEM implemented in the external microcontroller unit (MCU) applies additional digital signal processing to improve about 17-dB sensitivity. In the wake-up mode, the proposed RX saves the power dissipation by turning off all blocks except for the RXFE and wake-up preamble detector (WuPD). The WuPD following the RXFE provides a 17-dB sensitivity improvement in place of the MODEM of the data RX. Adopting the proposed SC-BFSK, in which other channels are inter-allocated between the BFSK tones of one channel, increases the number of channels while taking advantage of wide tone spacing, which improves the bit error rate (BER) in a multipath fading channel. To implement the ultra-low-power (ULP) SC-BFSK RX, the RXFE employs the 2:1 LO sliding-IF architecture and a band-pass filter (BPF)-based frequency-to-energy detection baseband demodulator. Implemented in 55-nm CMOS, the proposed RX, including both data and wake-up RXs, exhibits -123-dBm sensitivity with 0.39-kbps data rate and 81.92-ms wake-up latency, while the RX chip dissipates 0.88 mW.