XIE J,LI J H,WU S N,et al. Design of high stability and fast response LDO without external capacitors[J]. Microelectronics & Computer,2024,41(7):119-126. doi: 10.19304/J.ISSN1000-7180.2023.0522
Citation: XIE J,LI J H,WU S N,et al. Design of high stability and fast response LDO without external capacitors[J]. Microelectronics & Computer,2024,41(7):119-126. doi: 10.19304/J.ISSN1000-7180.2023.0522

Design of high stability and fast response LDO without external capacitors

  • To solve the issue of mutual interference between power source and circuit in optical communication integrated circuit and system-on-chip for optical communication, a high stability and fast response capacitor-less low dropout regulator (CL-LDO) is designed based on TSMC 65 nm CMOS technology. The LDO circuit comprises a bandgap reference module, a push-pull error amplifier, a power supply rejection(PSR) enhancement circuit, and a spike rejection circuit. The push-pull error amplifier with common gate input effectively reduces the output impedance. The amplifier's cross-coupling input significantly improves the slew rate in pass transistor. The internal topology structure solves the problem of low loop gain and poor symmetry. The Miller compensation is adopted to achieve system stability under full load capacitance of 0-100 pF. The main loop combined with spike rejection circuit improves transient performance. The power supply rejection enhancement circuit generates an adjustable negative capacitance to eliminate power supply ripple at the gate of the pass transistor, thus effectively improving the power supply rejection ratio in the intermediate frequency band of the LDO. Simulation results show that within a load current range of 0-100 mA, the LDO's overshoot and undershoot are 58 mV and 89 mV, respectively, the minimum recovery time is 1.2 μs. The worst-case phase margin is 64° over the full load range, the power supply rejection ratio is 99.2 dB@10 kHz in the unloaded state. The worst-case rate of load regulation rate and line regulation under different process corners are 0.016 mV/mA and 5.1 mV/V, respectively.
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