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Cross Coupled Level Shifting Low Voltage Wordline Driver for DRAM

IP.com Disclosure Number: IPCOM000121730D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 76K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+3]

Abstract

Disclosed is a new cross-coupled negative level-shifting low-voltage wordline driver for PMOS access-transistor DRAM. The new circuit functions at a lower power supply voltage than the previous circuit [*] and is more suitable for battery-operated low-power DRAM applications.

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Cross Coupled Level Shifting Low Voltage Wordline Driver for DRAM

      Disclosed is a new cross-coupled negative level-shifting
low-voltage wordline driver for PMOS access-transistor DRAM. The new
circuit functions at a lower power supply voltage than the previous
circuit [*] and is more suitable for battery-operated low-power DRAM
applications.

      Fig. 1 is the schematic diagram of the new isolated P-well NMOS
cross-coupled wordline driver for boosting the wordlines of PMOS
access-transistor DRAMs.  The circuit symbol for an MOS device with
two arrows pointing in opposite directions annotates an NMOS device
in an isolated P-well.  An isolated P-well is formed inside of an
N-well and is electrically isolated from the P-type substrate.  It
has the same number of transistors per wordline driver as the
previous circuit [*], but the negatively boosted clock applied to the
sources of the cross- coupled NMOS devices QN1 and QN2 are split to
two negatively boosted clocks GPLS1 and GPLS2.  The area increase due
to applying the two clocks is minimal, which is one of the most
critical considerations for DRAM wordline drivers.  The very nature
of the tightly spaced wordlines of a DRAM array precludes more
complicated configurations from consideration.

      Fig. 2 shows the waveforms of the activated wordline and the
two negatively boosted clocks GPLS1 and GPLS2.  The active wordline,
GPLS1, and GPLS2 are shown as solid, dotted, and broken lines,
respectively.  Note that GPLS1 and GPLS2 a...