A study and implementation of bandgap reference circuit and low drop-out linear regulator

[[abstract]]本論文對於低壓降線性穩壓器及其所使用的能隙參考電壓電路、保護電路、與運算放大器，作一完整探討並實現。低壓降線性穩壓器需要利用外部負載電容的等效串聯電阻(Equivalent Series Resistor，簡稱ESR)達成頻率補償，但是外部負載電容的ESR值無法精確的控制，本論文設計的低壓降線性穩壓器能夠在較寬的ESR值範圍下仍能達成頻率補償。本論文設計的能隙參考電壓則可提供一個不容易受溫度與供應電源影響的穩定輸出電壓，做為低壓降線性穩壓器所需的參考電壓。為了避免輸出功率電晶體因負載超過額定電流或功率電晶體超過額定溫度範圍，而導致元件損毀，本論文所設計的限流與過熱保護電路，在負載電流超過100mA時，會控制輸出功率電晶體使電流降下來；而當溫度高於140℃時，過熱保護電路會將低壓降線性穩壓器關閉，當溫度低於105℃時，則將重新開啟低壓降線性穩壓器。 為了能驗證本論文所設計的低壓降線性穩壓器，吾人採用國家晶片設計中心(CIC)所提供的TSMC 0.18μm 1P6M CMOS製程進行晶片的設計與實現。所設計的低壓降線性穩壓器工作輸入電壓為1.8-2V，提供1.5V的輸出電壓，最大負載電流為100mA，線性調節度低於2mV/V與負載調節度低於0.01mV/mA，電源拒斥比大於60dB。[[abstract]]In this thesis, a low dropout linear regulator that used bandgap voltage reference circuit, protection circuit, and operational amplifier is studied and proposed. Low-dropout linear regulators usually require the equivalent series resistance (ESR) of external load capacitor to achieve frequency compensation, but the value of ESR is hard to accurately control. The design of the proposed low-dropout linear regulator can achieve proper frequency compensation under a wide range of ESR values. The designed bandgap reference circuit has a stable output voltage and low sensitivity to temperature and supply voltage, to provide the desired reference voltage for the proposed low dropout linear regulator. To protect the device from destroyed by over current and temperature conditions, the designed protection circuit can limit the maximum load current at 100mA, and turn off the device as the temperature is higher than 140oC and turn on as the temperature is lower than 105 oC. The proposed low dropout linear regulator circuit is implemented in TSMC 0.18-μm 1P6M CMOS process provided by Chip Implementation Center (CIC). The low dropout linear regulator works under the input voltage of 1.8–2 V and provides up to 100 mA load current for an output voltage of 1.5 V. The line regulation and load regulation of the designed regulator is less than 2mV/V and 0.01mV/mA, respectively. The PSRR is more than 60dB.[[note]]碩