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Precharge Voltage Generator Based On Capacitor-charge Sharing

IP.com Disclosure Number: IPCOM000100284D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+3]

Abstract

Disclosed is a circuit generating a bitline precharge voltage for MOS memory applications. The circuit is based on the concept of capacitor- charge sharing and precharges the bitlines with a minimal di/dt noise. It also functions as a power supply decoupling capacitor during an active cycle and improves on-chip power supply regulation.

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This is the abbreviated version, containing approximately 85% of the total text.

Precharge Voltage Generator Based On Capacitor-charge Sharing

       Disclosed is a circuit generating a bitline precharge
voltage for MOS memory applications. The circuit is based on the
concept of capacitor- charge sharing and precharges the bitlines with
a minimal di/dt noise.  It also functions as a power supply
decoupling capacitor during an active cycle and improves on-chip
power supply regulation.

      The figure shows the bitline precharge voltage generator.  A
multiple of bitline pairs can be connected to the EQ node, but only
one pair is shown for simplicity.  At the beginning of an active
cycle, the signal PEQ changes from low to high and turns the PMOS
device 1 on, charging the capacitor CPRE to VDD.  Once charged, it
functions as a VDD decoupling capacitor, improving the power supply
regulation.  The sense amplifier is composed of the N- and P-
cross-coupled pairs shown in the dotted box.  Following the normal
operation of an active cycle, the bitline pair composed of BL and BLB
are latched by the signals DSLP and DSLN to the voltages VSLP and
VSLN.

      At the end of the active cycle, PEQ goes from high to low and
turns the PMOS devices 3, 4 and 5 on but shuts the PMOS device 1
off.  The charges stored in the bitline pair and the capacitor CPRE
are shared and generate the bitline precharge voltage VPRE given by:
VPRE  =   CBL (VSLN + VSLP) + VDD $ CPRE
CPRE + 2 CBL

      The required capacitance of the capacitor CPRE can easily...