Low-power Bandgap Reference with Soft Startup for Energy Scavenging Applications

Band-gap reference (BGR) is one of the important and indispensable analog circuits in integrated circuits. The design of BGR has been widely known. In most cases, the power supply voltage is assumed to be a constant value with a variation of ±10%. However, in the case of energy scavenging, the input voltage, which will be converted to the power supply voltage, varies in a wide range. Linear regulator such as Low Drop-Out Regulator (LDO) is used to produce the power supply inside the chip, however, the BGR cannot use LDO output as it power supply voltage since LDO uses BGR output as its reference voltage. In near field communication (NFC) systems, the input voltage varies with the distance between the reader and device. This work assumes the implementation of BGR in an NFC system where the supply voltage of BGR varies from OV to $5\mathrm{V}$. A BGR start-up mechanism for a wide input voltage range is proposed. The proposed start-up mechanism is implemented in 0.18um CMOS process and verified using Spectre simulation. The proposed BGR operates at 1.35~5.5V input voltage range. The temperature coefficient at a 1.7-V input voltage and a temperature range from −25 to 80°C is 21ppm/°C.