Challenges of integration of power supplies on chip - next generation technology...
Transcript of Challenges of integration of power supplies on chip - next generation technology...
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Challenges of integration of power
supplies on chip
Indumini Ranmuthu Ph.D
October 2016
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Why this is important:
There is significant trend in the industry towards power
density and integration in power supplies.
This trend is due to internet of things and ever decreasing
form factor.
This integration has given rise to many complex issues
such as power efficiency, building power supplies in
nanometer CMOS, power supply noise coupling and
increased thermal dissipation.
This talk discusses these issues and future trends.
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Applications where integration is critical
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4
The Internet of Things (IoT)
• The Internet of Things (IoT) • In the past: computers, tablets, phones
– In the future: almost anything!
• Home, car, office
• Toaster, fridge, tooth brush
• Light bulb, pill bottle, pop-tart package
– Volumes will be huge
– Market will be fragmented
• Where do we fit in?
– Tight spaces, low cost - power management in chip needs new solutions
– Ultralow power (energy harvesting, coin cells) needs new solutions
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Tablet power system
http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slyy028&fileType=pdf
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PMIC
Todays SoC power supply architectures
Wake
up
system
RF
module Digital
module ADCs,
analog
module
Refere
nce
module
LDO LDO LDO LDO
Digital
module
LDO
Core DC/DC DC/DC
5/12V Supply
~1.1V ~1.8V
GND
DC/DC
~3.3V
SOC
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Challenges
Size & cost - There are multiple power supplies in SoCs
with many external inductors and capacitors
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Size & Cost
Core DC/DC DC/DC
5/12V Supply
~1.1V ~1.8V
GND
DC/DC
~3.3V
Wake
up
RF
module Digital
module ADCs,
analog
Refere
nce
LDO LDO LDO LDO
Digital
module
LDO
L L L
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Size and Cost
• Higher switch frequency - > reduces inductor size
• SIMO converters -> reduces number of inductors
• Hybrid (SC & Buck) converters -> Reduces
inductor size
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Challenges
Efficiency
DC/DC –> Low Qg, Low RdsON MOS, New topologies
Processor/SoC core
Dynamic voltage scaling based on speed
Dynamic frequency scaling based on need
Adaptive voltage scaling based on process
variations
Turn off modules, Clock gating
http://www.ti.com/lit/ml/slyb186/slyb186.pdf
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Challenges
Transient response
SoC Load surge causing Supply voltage droop –
Getting worse with higher core current and lower core
voltage
Look ahead voltage scaling
Current mode DC/DC
Multi phase DC/DC
Too many pins
Power pins -> Reduce the number of major power
domains (increases the number of LDOs, reduces
efficiency)
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Noise coupling through supply & substrate
GND
SoC
Wake
up
system
RF
module Digital
module ADCs,
analog
module
Referen
ce
module
LDO LDO LDO LDO
Digital
module
LDO
Core DC/DC DC/DC
5/12V Supply
~1.1V ~1.8V
DC/DC
~3.3V
Solutions:
If source is in PMIC – higher sw freq, multi phase, multi level converters
If source is on SoC - - On chip decoupling, Isolation in substrate, Power bus Isolation
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Challenges
Thermal
SoC core heat dissipation -> core temperature based
Adaptive voltage and frequency scaling
LDO heat dissipation - > reduce drop out, external LDO
Need for low quiescent current (sleep , stand by)
-> At light load PFM, Pulse skip
-> Turn off blocks not used, clock gating
-> DC/DC Dead time reduction
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Automotive 12V Electrical system
challenges
• Wide Vin (3.5 – 40/60V)
• Stringent EMI requirements
• High power density – LED systems, Converters
• High temperature operation
• Reliability of safety critical systems -> Failure prediction,
Diagnostics, robust power switches
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Future trends in Integration
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Why it is difficult to integrate power
supply into SoC?
Semiconductor Process
Low on resistance LDMOS is not typically available in
state of the art digital process (e.g Fin FET)
High voltage Devices not available
High current metal system not available.
High voltage capacitors not available.
SoC cannot handle thermal dissipation of converter
Large inductor & capacitor needed for DC/DC
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Future trends - Process
Integration of active and passive components
– Trench capacitors in silicon
– Laminate inductors in MCM
– On silicon inductors
Finer geometry digital process with LDMOS
BCD processes with digital scaling to deep
submicron
0.35->0.25->0.18->0.13um->TBD digital with high voltage
LDMOS
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Future trends - Process
Lower Qg, Coss, Ron LDMOS in digital process
– Enables sophisticated digital control in PMIC
– Enables higher switching speed
Low ON resistance power process IC co-packaged with
a nanometer CMOS digital IC
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Future trends - Topology
High frequency converters
• Reduces inductor size
• Enables integration of inductor on PMIC
Multi level converters
• Use of low voltage FETs
• Reduces ripple, reduces inductor size
SIMO Converters
• Reduces number of inductors
• How to Mix large loads, light loads, load transients http://ims.unipv.it/~franco/ChapterBooks/10.pdf
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Future trends - Topology
Switched capacitor & Hybrid converters – Capacitor has
higher energy density than inductors
• Potential to integrate low load converter using trench cap
or external cap
– Issue in how to handle variable conversion ratios
• Hybrid SC & Buck topologies -> smaller inductor
Design Techniques for Fully Integrated Switched-Capacitor DC-DC Converters - Hanh-Phuc Le et al JSSC
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Switched capacitor power converters
Technology trends – IEEE SSC Magazine winter 2015
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PMIC - SoC potential future for the
industry
SoC
PMIC
L L
PMIC L
SoC
SoC
PMIC
L L
SoC
PMIC L
Higher freq DC/DC
SIMO
Integrated PMIC Today
PMIC, Batt Charger, Disply Driver, Wireless power
SoC L L
• High freq. Power MOS
• Hybrid converters
• Integrated Passives
L
Thermal
Challenge!
Efficiency
Challenge!