LDO regulator having an adaptive zero frequency circuit

A low dropout voltage (LDO) regulator comprising:

• an error amplifier having an amplifying stage and a pass device stage, said error amplifier generating a regulated voltage at an output of said LDO regulator;
• a current sensing circuit coupled to said pass device stage, said current sensing circuit generating a sense current that varies with an output current generated by said pass device stage at said output of said LDO regulator;
• and
• an adaptive zero frequency (AZF) circuit coupled to said current sensing circuit, coupled to a ground terminal of said LDO regulator, and coupled to an output terminal of said amplifying stage, wherein said AZF circuit provides a zero in a transfer function equation associated with a frequency response of said LDO regulator, and wherein said zero is located at a frequency which varies with said sense current so that to maintain stability in said LDO regulator and to improve transient response of said LDO regulator under a range of values for said output current.

A method of frequency compensating a low dropout voltage (LDO) regulator having an amplifying stage and a pass device stage, said method comprising the steps of:

• a) providing a capacitor and a variable resistance device in series between a ground terminal of said LDO regulator and an output terminal of said amplifying stage, wherein said variable resistance device has a resistance which inversely varies with a bias parameter;
• b) sensing an output current generated by said pass device stage;
• c) generating a sense current that varies with said output current;
• and
• d) generating said bias parameter for said variable resistance device in response to said sense current, wherein said resistance inversely varies with said sense current.