Post on 14-Apr-2018
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Linear Voltage Regulator
Presented By-Ashis Maity
Research Consultant
Advanced VLSI Laboratory
Indian Institute of Technology, Kharagpur
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 2
Why do we need voltage regulator?
Scaling the device to reduce power, area,
increase speed.
W ,L , tox , Hence VDD.
For 0.25u technology, tox=50A
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 3
Why do we need voltage regulator?
Faster Scaling of core supply than system
supply.
Voltage regulator required to fill the gap between
system supply and core supply.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 4
Applications & Properties of Linear
Voltage Regulator
Applications:
Used as voltage supply for highly analog
blocks like Sense amplifier, op-amp etc.
Properties:
Highly clean o/p voltage.
Lesser noise.
Poor efficiency.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 6
Transient Response of a Typical
Voltage Regulator
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 7
Specifications / Requirements
ILOAD : ILOAD_max to ILOAD_min.
VDDINT : VDDINT_typ 10%.
Settling time : Time required to settle VDDINT
within tolerance band at ILOAD transitionsPower Efficiency : Ratio of output power and
input power.
LOAD Regulation: How VDDINT varies with
ILOAD.LINE Regulation: How VDDINT varies with
VDDEXT.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 8
Driver Circuit with P-type pass tr.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 9
Advantages & Disadvantages of
Driver ckt with P-type pass transistor
Advantages :
Low dropout (LDO) .
Lesser area ( n-well process, without body
effected ).Higher gain - lesser input referred dc offset.
Higher load regulation capability.
Disadvantages:Frequency compensation is not easy.
Settling time is large.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 10
Driver Circuit with N-type pass tr.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 11
Advantages & Disadvantages of
Driver ckt with N-type pass transistor
Advantages:
Frequency compensation is easy.
Self feedback- act as source follower.
O/P impedance is small. Faster Response.
Disadvantages :
Dropout is more.
More area ( with body effect ).Lesser gain - Input referred offset is more.
Lesser load regulation capability.
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AVDL Lab-IITKGP Ashis Maity ( ashis.bec@gmail.com ) 13
Thank U!