A Low-Noise, Positive-Input, Negative-Output Voltage Generator for Low-to-Moderate Driving Capacity Applications

In this paper, a generic, low-noise, negative-voltage generator with wide tuning range and moderate driving capacity is presented. The highly integrated solution, incorporating a fully-integrated charge-pump and a regulator block, requires only one off-chip capacitor that can be shared with the supply decoupling capacitors. The fully integrated charge-pump operation is analyzed quantitatively, and a closed-form expression of its output impedance is derived. Powered from a single 3.3-V dc input, the output has a tuning range from -4.4 to +2.1 V for biasing applications, while the design supports a maximum load current of 250, 550, and 800 μA for the regulated output voltage at -3.0, -1.5, and 1.5 V, respectively. The measured steady-state ripple is under 3 mV
_PP
, while the noise voltage at the charge-pump operating frequency harmonics is below 130 μV
_rms
and the noise floor is under 5 μV
_rms
. The design is also the application verified with a gallium nitride power amplifier, thus further confirming its low-noise performance. Implemented in CMOS 180-nm process, the prototype chip occupies an area of 0.55 mm
²
.