Distributed LDO regulators in a 28 nm power delivery system

Abstract

A fully integrated power delivery system with distributed on-chip low-dropout (LDO) regulators developed for voltage regulation in portable devices and fabricated in a 28 nm CMOS process is described. Each LDO employs adaptive bias for fast and power efficient voltage regulation, exhibiting 64 ps response time of the regulation loop and 99.49 % current efficiency. An adaptive compensation network is also employed within the distributed power delivery system to maintain a stable system response within 25 to 105 °C and 10 % voltage variations with a capacitive load of more than 472 pF. No off-chip capacitors are required. Under a 788 mA load current step with 5 ns load edge, the power delivery system exhibits less than 15 % voltage droop for nominal input and output voltages, and a minimum dropout of 0.1 V. Each of the LDO regulators with the adaptive networks and bias current generator occupies 85 μm × 42 μm in a 28 nm CMOS process. All of the test measurements are performed in a distributed power delivery system of six on-chip LDO regulators within a commercial high performance portable device. The proposed system is the first successful silicon demonstration of stable fully integrated parallel analog LDO regulators.