next generation power modules

next generation power modules
Next Generation
Power Modules
Further Simplify
Power Design
By: Robert Nicoletti
Manager, Strategic Application Engineering
Maxim Integrated
1
Executive Summary
A sound discrete power supply design requires a high level of expertise and is timeconsuming to design. Power modules offer an easier path, in a ready-to-use plug-and-play
reliable design for rapid prototyping or end use.
A new generation of power modules on the market today offers greater integration, for a
smaller system-in-package power solution. New process and packaging technologies have
enabled these devices to become more compact and operate with higher efficiency, while
eliminating the daunting task of designing a worry-free power supply. This enables system
designers to spend greater time on the core design, for faster time to market.
1
Next Generation Power Modules Further
Simplify Power Design
time to market or—if not resolved—even cause the
system to fail in the field.
The fundamental advantage of power modules is that
they allow system designers to focus on their core IP
while leaving power supply design to someone else.
But now, yesterday’s off-the-shelf PCB power modules
and bricks have given way to even better, and smaller,
“System-in-Package” modules.
Furthermore, discrete power supply designs require
many external components, which in turn require time
and effort to source, stock, order, and surface-mount, and
whose availability can be challenging to ensure. Discrete
power designs also usually mean a larger PC board
layout, which takes up valuable real estate at a time
when—more than ever—space is at a premium.
These next-generation power supply modules
take today’s new design challenges into account.
Technological advances have made modules easier to
use, while also decreasing the overall size and reducing
the total BOM. The best of these next-generation
modules have even higher efficiency than before, are
pin-to-pin compatible across different voltages and
currents, and are designed with an easy migration path
for cost reduction.
Power Supply Design: Not an Easy Task
It’s not a simple task to design a robust power supply
from the ground up, and that’s even more true of one
that includes a switching regulator integrated circuit
(IC). The typical approach,
a complicated mix of
discrete components,
requires specialized
expertise and knowledge
to keep the circuit free of
problems. Power supply
issues are problematic
because they can lengthen
Power Modules Are the Solution
Advancements in smaller-geometry processes, IC design,
and integrated package technologies now allow module
manufacturers to combine the passive components
needed for a power supply circuit, along with the
base ICs, into a single, small power supply solution.
Synchronous switching regulators include integrated
FETs, which are smaller, more efficient, and more
accurate than older switchers. The latest power module
solutions merge these new synchronous switchers with
components such as resistors, capacitors, MOSFETs and
inductors, for a simple-to-use hybrid power module that
reduces solution size, cost and layout complexity.
Advancements...now allow
module manufacturers to
combine passive components,
along with the base ICs, into
a single, smaller power
supply solution.
2
Not All Power Modules Are the Same
Many power modules on the market today are simpler to
use than ICs but don’t fully address all design challenges.
An ideal module speeds time to market, by combining
a low total cost of ownership with other key design
benefits like these:
• High efficiency and low power dissipation, based on
customer-proven robust ICs
• Small size, achieved by integrating more components
• Easy to use, with pin compatibility across voltages and
currents for design flexibility
• Flexible, with a transparent cost reduction option ideal
for migrating from module to IC for volume production
SWITCHING POWER
SUPPLY CONTROLLER
MOSFET POWER
SWITCHES
The result is a reliable new generation of System-inPackage (SiP) power solutions that eliminates discrete
design problems and addresses the aforementioned key
design needs, allowing engineers to spend their time on
other critical design areas (Figure 1).
Proven Synchronous Regulators as a
Foundation
Improvements in IC processes and designs have led to
the integration of the MOSFET transistors utilized in
switching power supplies. This integration, in turn, has
led to the development of synchronous rectification
power supplies that have revolutionized the DC-DC
power market, especially in the high voltage application
space. The latest synchronous buck converters provide
extraordinarily high efficiency, cooler operation and
smaller size.
INDUCTOR
POWER
MODULE
COMPENSATION
COMPONENTS
OTHER
PASSIVES
Figure 1. Power modules integrate all the key components
needed for a complete power supply
3
FEATURED TECHNOLOGY
Advantages of Synchronous Versus
Non-Synchronous Power ICs
Figure 2 shows the difference between synchronous
and nonsynchronous power designs. Traditional
non-synchronous converters use an external Schottky
diode, to rectify and conduct the output inductor
current during the high-side transistor off-time. In
theory, this technique is simple. Unfortunately, in
practice, it’s difficult to design in—and harder still
to control, even though it was commonly used for
several decades. Its biggest drawback is that the diode
dissipates a lot of heat due to its forward voltage drop,
so the resulting system is not very efficient.
A synchronous converter replaces the external
rectification diode with an integrated low-side
power MOSFET. Compared to the diode on the
non-synchronous converter, the MOSFET’s low
resistance causes a much smaller voltage drop;
the MOSFET can also be turned off when not
needed. Hence, power loss during the conversion
is significantly reduced. That means the circuit
runs cooler—and more efficiently. Both the
rectification low-side MOSFET and the once-external
compensation circuitry are now part of the IC itself.
To better explain the benefits of this technology,
let’s do a quick power loss calculation to compare
synchronous and non-synchronous solutions.
IOUT
NON-SYNC
VIN
VD
As you can see, the synchronous solution reduces the
power loss in the rectification diode by 60 percent!
And that is cool—literally.
The corresponding thermal images clearly indicate
how much cooler the synchronous DC-DC converter
is operating, compared to its nonsynchronous
counterpart. This is important because heat can
reduce the lifespan of an electrical component.
To quote Svante Arrhenius, “For every 10 degree
reduction in temperature, the circuit’s life doubles.” It
follows that a 30°C temperature difference means that
the synchronous solution should last 8 times longer
than the non-synchronous solution.
IOUT
SYNCHRONOUS
VOUT
Voltage drop across diode VD = 0.5V
PD = VD xIOUT x (1-VOUT/VIN) = 0.99W
VIN
RON
VOUT
RON = 0.8Ω
Power dissipation across the FET:
PFET = RON xI2OUT x (1-VOUT/VIN) = 0.40W
TOTAL SOLUTION POWER LOSS = 2.3W
TOTAL SOLUTION POWER LOSS = 1.1W
30°C COOLER
Figure 2. Synchronous vs. non-synchronous rectifier power dissipation
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By integrating the compensation circuitry, synchronous
rectification boosts the accuracy of feedback regulation.
But more dramatically, built-in compensation across the
output voltage range eliminates the need for external
components, notably reducing component count and
footprint size. An additional benefit is high internal
reference voltage accuracy, which provides more precise
voltage regulation—close to ±1% over an extended
operating temperature range.
Using these new integrated FET switching regulators
with synchronous rectification as a foundation for
power modules, suppliers can offer the same benefits
of high efficiency, cooler operation, smaller size,
and more precise voltage regulation. For example,
Maxim integrates its Himalaya ICs together with other
components, to create the Himalaya family of
power modules.
How Power Modules Simplify the
Design Process
Even with these advanced synchronous buck ICs, a
robust power supply still has numerous requirements
and challenges to overcome. A designer must assess
the input voltage, output voltage, load current,
temperature, noise immunity and/or emissions, to
name a few. Some of the most difficult challenges
associated with switching power supply designs include
external component choice, component placement,
PCB layout, and controlling issues like electromagnetic
interference (EMI), radio frequency interference (RFI),
and radio frequency susceptibility (RFS). Any of these,
if unchecked, may introduce electrical noise that can
couple into and out of the power circuit.
When choosing external components for a discrete
power supply, careful judgment is critical. For example,
inductors of the same inductance value can have
different saturation points, causing problems when
fast transients demand high currents. There are many
styles of inductors, all with different factors that control
their specifications, including the exact magnetic core
material, coil shape, separation between turns, frequency
response, DC resistance, quality factor (Q), and shielded
vs. non-shielded. Choosing the wrong inductor may
cause problems such as instability, spiking at the input
or output, or even complete failure, if the inductor is not
properly suited for the system’s power requirements.
Capacitors can also cause instability, if not properly
chosen, since their value may vary over frequency,
voltage and temperature.
With power modules, some external components
are already integrated, removing a great deal of risk.
In fact, it’s now possible to integrate everything from
the switching power supply controller to the MOSFET
power switches, inductor, and other passive components
needed for proper compensation and bias, with only
four or five minimum external components required
for operation. All integrated components are carefully
chosen for optimal performance, taking the guesswork
out of design. Engineers are free to focus on choosing a
suitable off-the-shelf power module that matches their
exact power supply requirements.
Choosing the correct components for a discrete power
circuit is important, but equally important is properly
placing them near the IC, which requires a high level
of skill and expertise. The designer needs to keep in
mind the length and size of the high-current paths,
be concerned with high-frequency nodes, and take
precautions with ground return paths to both the IC
and the input power supply. Inductors and capacitors
located too far from the IC can cause problems, by
increasing parasitics and resistance within the highcurrent loop. (Most modules on the market utilize
shielded inductors; these help to lower the EMI
associated with switching regulators, making it more
predictable.) Compensation and feedback circuitry
can also be affected by ground noise if not properly
designed. Sealing modules into encapsulated packages
can help protect their ICs from the PCB layout issues
so prevalent in discrete power designs. Because the
module is soldered down like a standard IC, and the
compensation circuit, FETs and inductor are all internal,
the ground configuration is well known, and designed
to control the ground currents near sensitive devices.
This control helps safeguard the power circuits from
ground bounce and other system level noises that can
be injected into the compensation circuit, ultimately
resulting in a more efficient and reliable power supply.
5
Smaller is Better
Besides eliminating many of the hurdles typically associated with designing a robust power supply, these nextgeneration power modules have the added benefit of being much smaller than discrete power solutions that use PWM
controllers or even integrated FET switching regulators. Over the years, power supply circuits have progressed from
simple power controllers with all external components (Figure 3A), to power converters with IC integration that use
an external inductor but fewer additional external components (Figure 3B), to their latest iteration, a more compact
power module (Figure 3C). Himalaya power modules, for example, require as little as four to five small external
components: input capacitor, output capacitor, two resistors to set the output voltage, and possibly a capacitor for soft
start. Figure 3 shows this progressive integration of power solutions, along with the footprint size associated
with each.
CURRENT
LIMIT
FREQUENCY
SETTING
VIN
VIN
CONVERTER
MODULE
VOUT
CONTROLLER
VOUT
COMPENSATION
VIN
VOUT
BOOST CAP
BIAS
PGOOD
BOOST CAP
BIAS
PGOOD
3A. MAX15046 SYNCHRONOUS BUCK CONTROLLER
Figure 3. Progressive Integration of power solutions
3B.MAX17503 SYNCHRONOUS BUCK CONTROLLER
3C.MAXM17503 MODULE
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Convenience and Flexibility Are Key
2.8mm is another key attribute for the next generation
of power modules. It enables their use in mezzanine card
applications where height clearance is important, and
also makes it easier to integrate heat sinks—particularly
important for high-power applications that need to
disperse a lot of heat (Figure 5).
As you can see, the latest power modules clearly have a
smaller footprint. But this is only one advantage of using
modules. Another is design simplicity.
A new kind of layout configuration that brings the pins
to the periphery of the package, via a QFN-like pin out,
makes PCB layout easy and less expensive for designers.
Locating key signal pins at the perimeter of the package
eliminates the need for multilayer boards that use vias
to route to center pins located on the module’s interior,
as is the case with a ball or grid array type module
(Figure 4). Perimeter pin location also creates room on
the underside of the module for exposed pads, which
can help dissipate heat away from the module for even
cooler system operation. Multiple separate exposed
pads provide additional protection, by isolating sensitive
module areas from each other. Package height as low as
MAXM17504
5V to 60V
9mm
6.5mm
7
GND SYNC
2.8mm
2.8mm
Figure 5. Just two examples of Maxim’s Himalaya modules, small in
both size and height
MAXM17504
9mm x 15mm x 2.8mm
RUN/
SS
ADJ PGOOD
BANK 3
SHARE RT
BANK 2
5
GND
4
BIAS
3
RESET EN
FIN
6
AUX
2
N.C.
1
SYNC
2
SS
3
CF
4
BANK 1
BANK 4
FB
5
VOUT
VIN
RT
6
1
N.C.
A
B
10mm
15mm
COMPETITIVE PART
11.25mm x 15mm x 4.32mm
8
MAXM17516
2.5V to 5V
C
D
E
DIFFICULT FOR PCB ROUTING
F
G
H
J
K
L
7
29
28
IN
PGND
27
26
BST LX
LX
LX
LX
24
23
22
21
LX
20
LX
19
LX
18
OUT
17
OUT
16
OUT
25
EP2
LX
EP1
SGND
PGND
EP3
OUT
8
9
10
MODE VCC SGND
11
PGND
12
13
14
15
OUT OUT OUT OUT
BIG EXPOSED PADS
Figure 4. Pinout comparison between Maxim’s QFN approach and an older grid array layout
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Migrate with Ease Across Voltages and Currents
Power requirements can change frequently throughout the various design phases of a project. So why should
customers be forced to redesign and re-spin their boards whenever their voltage or current requirements change? It’s
costly—and time-consuming.
Look for power module families that offer pin-to-pin compatible options across different current ranges and voltages.
This allows the same layout to use different modules interchangeably with no impact to the PCB, and thereby
accelerate time to market.
Cost Reduction Path: Migration to Discrete ICs
Some designers are hesitant to adopt power modules because they aren’t as customizable as discrete power
solutions, and are typically priced higher. The missing link, which is now a reality, is the ability to migrate. Today’s
designers can start with a module, for rapid development. They then have the option to seamlessly migrate to a
solution using the identical IC, in discrete form. This flexibility optimizes both performance and costs when it’s time
for high-volume production, and can be invaluable to designers who want the best of both worlds.
Simplify Design
Innovation in IC process and packaging technologies has allowed for more integrated power modules than ever, at
both IC and package levels. These next-generation power modules strip away all the complex problems associated
with discrete components, while providing a complete and reliable power supply solution. They are highly efficient,
are virtually immune to most PCB noise, and have more predictable EMI performance than the older nonsynchronous
designs, while also operating at much cooler levels. Such power modules allow system-level designers with limited
time and resources to quickly design the power circuit they need, so they can spend more time on other, more
important design areas.
Maxim Integrated has taken these power modules to a new level. Its modules use customer-tested Himalaya
synchronous buck regulator ICs, with their cooler operation advantages and small size benefits. They are designed
with the engineering mind, from their smaller form factor with minimal external BOM components, convenient
QFN-like pinout, and flexible pin-to-pin compatibility across different voltages and currents, to their easy migration
path from modules to ICs in high-volume projects.
Power modules will continue to evolve toward more integration, cooler operation and a smaller size, with an emphasis
on cost reduction. With these advances, power design has never been simpler or easier.
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Learn more
For more information, visit:
www.maximintegrated.com/powermodules
About the Author
Robert Nicoletti has 15 years’ experience in the semiconductor industry with Maxim Integrated as an applications
engineer, and has managed an applications team for 9 years. His experience spans a wide range of systemlevel disciplines such as system power, interface and audio solutions. He holds a bachelor’s degree in Electrical
Engineering from San Jose State University.
© 2015 Maxim Integrated Products, Inc. All rights reserved. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products,
Inc., in the United States and other jurisdictions throughout the world. All other company names may be trade names or trademarks of their respective owners.
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