A Direct Feedback FVF LDO for High Precision FMCW Radar Sensors in 65-nm CMOS Technology

Abstract

A direct feedback flipped voltage follower (FVF) LDO for a high-precision frequency-modulated continuous-wave (FMCW) radar is presented. To minimize the effect of the power supply ripple on the FMCW radar sensor’s resolution, a folded cascode error amplifier (EA) was connected to the outer loop of the FVF to increase the open-loop gain. The direct feedback structure enhances the PSRR while minimizing the power supply ripple path and not compromising a transient response. The flipped voltage follower with a super source follower forms a fast feedback loop. The stability and parameter variation sensitivity of the multi-loop FVF LDO were analyzed through the state matrix decomposition. We implemented the FVF LDO in TSMC 65 nm CMOS technology. The fabricated FVF LDO supplied a maximum load current of 20 mA with a 1.2 V power supply. The proposed FVF LDO achieved a full-spectrum PSR with a low-frequency PSRR of 66 dB, unity-gain bandwidth of 469 MHz, and 20 ns transient settling time with a load current step from 1 mA to 20 mA.

Single-Stage CMOS Operational Transconductance Amplifiers (OTAs): A Design Tutorial

“…When I D3 = I D4 > I D5 and the rising step response is applied, the sourcing current I D4 − I D5 flows through M 9 , which has a different direction of the sinking current I D3 flowing through M 7 and M 11 . SR F,FC_OTA also follows (19) despite the increasing current. As a result, setting I D3 and I D4 as larger than I D5 to increase SR R,FC_OTA and SR F,FC_OTA is not effective since SR R,FC_OTA and SR F,FC_OTA are independent of I D3 and I D4 .…”

“…Moreover, in order to further increase the A o , the folded cascode structure has been adopted as the first stage of a multi-stage OP-AMP [36]. Lastly, the current mirror OTA has been used as the error amplifier of DC-DC converters and LDOs [18][19][20] or as the feedforward amplifier of neural recording amplifiers [13,14]. In power converters, the error amplifier often needs to be fast since the output voltage or the load condition can be changed rapidly.…”

“…OTA-based integrators with an inherent high gain and low-pass frequency response have been used in delta-sigma analog-to-digital converters (ADCs) [10][11][12]. Moreover, OTAs themselves have served as feedforward amplifiers of closed-loop systems such as capacitively coupled instrumentation amplifiers (CCIAs) [13][14][15] and power ICs [16][17][18][19][20] thanks to their high gain performance. The versatility and wide applicability of OTAs make them indispensable in various analog and mixed-signal circuit designs, emphasizing the paramount importance of OTA design.…”