A 0.8V 0.8mm2 bluetooth 5/BLE digital-intensive transceiver with a 2.3mW phase-tracking RX utilizing a hybrid loop filter for interference resilience in 40nm CMOS

Abstract

This paper presents a low-voltage (0.8V) ultra-low-power Bluetooth 5(BT5)/Bluetooth Low Energy(BLE) digitally-intensive transceiver for IoT applications. In comparison to BLE, BT5 has a 2x higher data-rate and 4x longer range, while having >8x longer packet. The BLE prior arts [1-5] have made significant efforts to minimize the power consumption for longer battery life, as well as the chip area. However, the prior-art Cartesian BLE radios consume namely 6 to 10mW [1-3] to achieve a <-94dBm sensitivity but with a relatively high supply voltage (VDD) (>1.0V). Operating a BLE RF transceiver at a lower VDD (e.g., <0.85V) not only extends the battery life by up to 50% [3], and reduces the Power-Management-Unit complexity, but also can accommodate a wider range of energy sources (e.g., harvesters). A recent single-channel phase-tracking RX [5] demonstrated a potential to reduce the chip area and the power consumption at a VDD down to 0.85V. However, it suffers from a degraded sensitivity due to a poor deviation frequency control and an excessive loop delay, limited ACR (Adjacent-Channel-Rejection) due to the digitally-controlled-oscillator (DCO) side-lobe energy, and an undefined initial carrier frequency due to the lack of a PLL/FLL that could have a risk of tracking to an interference. This work presents a fully-integrated 0.8V phase-domain BT5/BLE-combo transceiver, including a PHY-layer digital baseband (DBB), and addresses the above-mentioned issues by employing two key techniques: 1) a hybrid loop filter with a loop-delay compensation for DCO side-lobe suppression to enhance interference tolerance, and 2) an all-digital PLL(ADPLL)-based digital FM interface shared between RX and TX is employed, including a deviation frequency calibration, and it also precisely defines the initial frequency. Moreover, the PHY-layer DBB that supports a packet-mode phase-tracking RX operation is also demonstrated.