An Improved Low-EMI Fast-Transient-Response Buck Converter Suitable for Wireless Sensor Networks With New Transient Accelerated Techniques

Abstract

This paper proposed an improved low-electromagnetic-interference (EMI), high-efficiency fast-transient-response buck converter suitable for wireless sensor networks with new transient accelerated techniques. The proposed second-order delta-sigma modulator used the noise-shaping technique and the oversampling theorem to reduce the electromagnetic interference of the output spectrum. And then added the transient acceleration loop to accelerate the transient response also lowers the undershoot and overshoot voltage when the load current changed. The proposed converter has been implemented with TSMC <inline-formula> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> 1P6M process, and the chip area is <inline-formula> <tex-math notation="LaTeX">$1.19 \times 1.19$ </tex-math></inline-formula> mm² (including PADs). The measured results show that when the output voltage is 2 V and the load current changes from 100 mA to 500 mA and from 500 mA to 100 mA, the transient responses are <inline-formula> <tex-math notation="LaTeX">$4 ~\mu \text{s}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$3 ~\mu \text{s}$ </tex-math></inline-formula>, and transient voltages are 18 mV and 30 mV, respectively. Compared to the traditional continuous-time delta-sigma-modulation converter improved <inline-formula> <tex-math notation="LaTeX">$3 ~\mu \text{s}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$7 ~\mu \text{s}$ </tex-math></inline-formula>. The maximum output voltage ripple is 30 mV. The output-to-noise ratio (ONR) is 72.15 dB with the sampling frequency of 10 MHz. When the load current is 100 mA and the output voltage is 2.5 V, the peak efficiency is 90.8&#x0025;.