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On-Chip Voltage Regulators With Improved Ripple Rejection

IP.com Disclosure Number: IPCOM000099922D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 83K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+2]

Abstract

New CMOS on-chip voltage regulators with improved ripple rejection are disclosed. Each new circuit utilizes an additional reference level generator to power the differential amplifier which controls the series regulating element operating in the source-follower mode and, thereby, reduces the ripple noise coupling from the external supply to the regulated supply. The new techniques are applicable when the dropout voltage (X VCC - VDD(INT) in the figures) is large enough and can also be applied to BiCMOS regulator circuits.

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On-Chip Voltage Regulators With Improved Ripple Rejection

       New CMOS on-chip voltage regulators with improved ripple
rejection are disclosed.  Each new circuit utilizes an additional
reference level generator to power the differential amplifier which
controls the series regulating element operating in the
source-follower mode and, thereby, reduces the ripple noise coupling
from the external supply to the regulated supply.  The new techniques
are applicable when the dropout voltage (X VCC - VDD(INT) in the
figures) is large enough and can also be applied to BiCMOS regulator
circuits.

      Fig. 1 shows the first new regulator circuit for n-well CMOS
technologies where the differential amplifier (consisting of MN2-MN4
and MP1-MP2) operates from a reference potential VCC(INT) generated
using MN5 and MP3. The potential is set by the current flowing
through R1, MP3, MN5, and the VREF generator and by the sizes of MN5
and MP3.

      This new circuit has a good high-frequency ripple rejection at
VCC(INT) because a noise on the external supply node VCC is filtered
out by R1-C1.  Thus, ripple noise coupling to the node Y and then to
VDD(INT) is much reduced. Low-frequency drift of VCC appears at
VCC(INT) with some attenuation determined by R1 and the effective
small-signal resistance of the MP3-MN5-VREF circuitry.  Although the
attenuation factor may be small, as long as the regulator feedback-
loop responds faster than the drift period, the output VDD(INT) will
be regulated to VREF and have a good external...