This paper demonstrates a Bluetooth Low-Energy (BLE) transceiver (TRX) achieving ultra-low-power (ULP) operation for Internet-of-Things (IoT) applications. As more and more devices will be connected and access to the Internet, the wireless traffic will be extremely crowded in the 2.4GHz ISM band. To coexist with all the wireless devices without being interfered by co-channel and out-of-band (OB) signals, a BLE receiver (RX) should have very high adjacent-channel rejection and very high blocker tolerance. At the same time, the total power consumption should be minimized for longer battery life. In this work, the TRX utilizes a wide loop-bandwidth All-Digital PLL (ADPLL) as a central component for transmitter (TX) modulation, RX analog data digitization, and phase synchronization. The single-channel demodulation method is adopted for cutting half of the analog baseband circuit to further reduce the power consumption while maintaining a high interference rejection. This BLE TRX achieves the lowest energy consumption among the state-of-the-art works in the comparison table [1-5] while satisfying all the interference requirements with sufficient margins.