Distributed LDO regulators in a 28 nm power delivery system
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.
KeywordsDistributed power delivery Voltage regulators On-chip LDO PVT variations Adaptive compensation Adaptive biasing Stability 28 nm
This research is supported in part by the Binational Science Foundation under Grant No. 2012139, the National Science Foundation under Grant No. CCF-1329374, and by a grant from Qualcomm Corporation.
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