A 92%-Efficiency Hybrid Envelope Tracking Modulator Based on 3-Level Hysteresis-Controlled Buck Converter with Capacitor Current Integration Sensor

This paper presents a 20 MHz bandwidth, 92%-efficiency, hybrid envelope tracking modulator with a 3-level hysteresis-controlled buck converter in parallel with a Class-AB linear amplifier for LTE application. Compared with the 3-level PWM control, this control method has fast loop response with the improvement of efficiency. The 3-level hysteresis controller controls LA output current and flying capacitor voltage of switching stage concurrently without synchronization clocks. And capacitor current integration sensor is embedded in the hysteresis-control loop to solve the current sensor problem. The designed Class-AB linear amplifier with rail-to-rail input stage and maximum current selection achieves a small signal -3 dB bandwidth of 238 MHz. With an optimized design in 65 nm CMOS technology, the modulator can deliver 0.92 W output power to a 4Ω load, achieving a maximum efficiency of 92% for LTE-20MHz application.