Integrated voltage regulators with high-side NMOS power switch and dedicated bootstrap driver using vertical body channel MOSFET under 100 MHz switching frequency for compact system and efficiency enhancement

Abstract

In this paper, integrated voltage regulators (IVRs) with a cascode bridge circuit composed of a high-side (HS) NMOS power switch and a dedicated bootstrap driver using a vertical body channel (BC) MOSFET are proposed for improving efficiency under 100 MHz switching frequency. The proposed circuit utilizes the back-bias effect free characteristic of the vertical BC MOSFET without additional well structures such as a triple-well structure for efficiency enhancement. Power switching of twice the process voltage V MAX with an HS NMOS power switch is realized by a novel circuit technique that directly connects the bootstrap node to the gate of an n-type MOSFET connected to the input voltage. Moreover, by using a vertical BC MOSFET free from the back-bias effect, the on-resistance increase of the HS NMOS power switch due to the high input voltage is significantly suppressed, and the drain-to-source voltage of MOSFETs in the off-state is distributed uniformly in comparison with that of a planar MOSFET. The proposed IVR of 3.3 V input voltage and 1.2 V output voltage is designed and simulated by HSPICE. Additionally, the power transistor size dependence of efficiency indicated that the proposed IVR can achieve a 4.2% higher peak efficiency than the conventional IVR with a 26% smaller total power transistor size.

Loss analysis and optimum design of a highly efficient and compact CMOS DC–DC converter with novel transistor layout using 60 nm multipillar-type vertical body channel MOSFET

“…11) Thanks to the features of the vertical BC MOSFET, performance improvements are reported in several circuits such as charge pump, level shifter, and logic. [21][22][23][24][25][26][27][28][29] Partic- ularly for CMOS DC-DC converters, owing to the back-bias free characteristic of the vertical BC MOSFET, it is reported that a high-side n-type MOSFET (HS-NMOS) topology, which enhances the conversion efficiency compared with a high-side p-type MOSFET (HS-PMOS) topology and is generally applied to converters using planar CMOS devices, will be available without additional well structures such as a triple-well structure. 24) On the other hand, a multipillar-type vertical BC MOSFET, which is shown in Fig.…”

“…[25][26][27][28][29] In particular, it has been reported that a DC-DC converter with a cascode bridge circuit composed of a HS NMOS power switch and a dedicated bootstrap driver using a vertical BC MOSFET improves efficiency under 100 MHz switching frequency. 24) For a conventional noncascode power switch composed of multipillar vertical BC MOSFET, it is reported that a large drain current can be attained by locating the bottom contact among silicon pillars because the effect of the parasitic resistance of the bottom diffusion region is minimized. 20) However, even if a highly efficient circuit technology for a cascode CMOS DC-DC converter using vertical BC MOSFET had been proposed in Ref.…”

“…20) However, even if a highly efficient circuit technology for a cascode CMOS DC-DC converter using vertical BC MOSFET had been proposed in Ref. 24, a highly efficient and compact transistor layout of multipillar-type vertical BC MOSFET for the cascode power switch has not been reported yet.…”

“…[21][22][23][24][25][26][27][28][29] Partic- ularly for CMOS DC-DC converters, owing to the back-bias free characteristic of the vertical BC MOSFET, it is reported that a high-side n-type MOSFET (HS-NMOS) topology, which enhances the conversion efficiency compared with a high-side p-type MOSFET (HS-PMOS) topology and is generally applied to converters using planar CMOS devices, will be available without additional well structures such as a triple-well structure. 24) On the other hand, a multipillar-type vertical BC MOSFET, which is shown in Fig. 3, has been proposed and it is verified that it has superior device performances, especially for current drivability compared with a singlepillar-type vertical BC MOSFET.…”