A 0.2V energy-harvesting BLE transmitter with a micropower manager achieving 25% system efficiency at 0dBm output and 5.2nW sleep power in 28nm CMOS

Massive deployment of wireless sensor tags (e.g. iBeacon) will only happen if batteries and their replacement effort are avoided. Self-powering by harvesting the ambient energies like indoor solar and thermal gradient is prospective [1], but their inconstant sub-0.5V output hinders their utility. Adding boost converters and regulators inevitably worsens the system efficiency and integration level. This paper reports an energy-harvesting Bluetooth Low-Energy (BLE) transmitter (TX) (Fig. 28.5.1). It features a fully integrated micropower manager (μPM) to limit the sleep power and tolerate variation of the energy-source voltage (V
DD, EH
) down to 0.2V. U=An ultra-low-voltage (ULV) VCO and Pa, and a passive-intensive type-I PLL are proposed. Fabricated in 28nm CMOS, the TX exhibits a 25% system efficiency at 0dBm output (P
out
).