Power Management:
Design Challenges and Solutions
Power supplies and related parts are invariably critical in any system design. Ask anyone who's ever hit the power button on their computer and gotten nothing but a dark screen. Yet the system designer often does not address the power system until the very last. Instead designers focus on the system blocks that provide differentiation to their final product -- areas like digital signal processing (DSP), for example.
As a result, most designers are looking for a quick and effortless power management solution for their system designs. Power supply circuits must be easy to design with. They must interface readily with advanced processors. And they must handle the demands of today's advanced systems. While those demands certainly vary depending on the specific application, several are common to all. These global demands include:
- A move towards lower and mixed-voltage systems
- The desire for lower power consumption in battery powered applications
- The ability to drive large loads in a small package
- The ability to support emerging standards
Texas Instruments (TI) has a long history of designing and manufacturing an extensive selection of leading-edge power management products. According to Dataquest, TI is the number two supplier in the market for power management devices. And with a variety of application notes, designer's guides and evaluation modules, TI's power management products can be easily designed into most systems. Continuing in this tradition, TI stands ready to meet the design challenges for today's power management products.
Design Challenge #1: Lower and Mixed Voltages
Five volts, 3.3 volts, 2.5 volts and 1.8 volts and below. The steady march to lower voltages in digital systems continues. Looking specifically at DSPs, core voltages have dropped from 5V to 2.5V and the current target is 1.8V. It's a logical move given that lower voltages enable higher component densities, faster speeds and lower power consumption. It does however place additional demands on the power supply circuits. Noise levels that are acceptable in a 5V design are not acceptable at lower voltages. Tolerances on the voltages supplied to a microprocessor or DSP become tighter.
Designers must select the appropriate type of power supply regulator for their system -- linear versus switching. They must also take care in the printed circuit board layout -- minimizing noise and providing clean power to the system.
In addition, designers must also deal with mixed voltage systems. Many DSPs today offer a 2.5V core and 3.3V input/output (I/O). The mixed voltages allow the DSP core to operate at the lowest possible voltage while the I/O remains at the voltage that is prevalent with traditional interface devices.
Manufacturers of power supply circuits such as TI have met the design challenge of lower and mixed voltages with the introduction of leading-edge devices. For example, TI introduced the industry's first 2.5V supply voltage supervisor in November 1997. A new family of power supply controllers introduced specifically for the DSP market -- TPS56xx -- is offered in output voltages of 1.5V, 1.8V, 2.5V and 3.3V. With this range of voltages, designers can more easily implement mixed voltage systems -- using a 2.5V device for the DSP core and a 3.3V device for I/O functions.
Design Challenge #2: Lower Power Consumption for Battery-Powered Applications
The demand for portability in everything from computers to phones has resulted in a plethora of battery-powered applications. Given that all batteries have a finite life, this creates immediate pressure to lower power consumption. Device manufacturers are attacking the power consumption issue across the board using a variety of approaches including the move to lower system voltages that was discussed earlier.
Other approaches include featuring a sleep state. In this state, the device uses much less current than when fully operational while at the same time it is able to quickly resume full operation when triggered by an external event. Sleep states are the foundation of various initiatives -- all aimed at providing computers with an "appliance-like" turn on capability.
The micro-power low drop out regulator introduced by TI last year directly addresses battery life issues. The device -- TPS71025 -- uses a low quiescent current that is independent of load. It also offers a low sleep state current. Both of these prolong battery life making the regulator ideal for applications such as notebook computers, personal digital assistants and digital cameras.
Design Challenge #3: Ability to Drive Large Loads in a Small Package
Small is big in power supply design. Designers are packing more and more features into their systems -- video, sound and fast Internet access, to name just a few. All of that functionality must fit into the same or smaller footprint as the previous equipment generation. Obviously, space is at a premium and the less spent on power supply blocks the better. This is at the heart of the push for smaller and smaller power management device packaging even while the functionality increases.
The SOT-23 integrated circuit package is an excellent example of this trend. It stands for small-outline transistor housing and measures a mere 3.6 by 1.6 by 1 millimeter. A number of power supply circuits are now available in the tiny SOT-23 package. For example, in June 1998, TI introduced a family of supervisory circuits for low voltage microprocessor systems -- TPS3823 and TPS3824. The devices provide circuit initialization and timing supervision. They are available in 2.5, 3.0, 3.3, and 5.0V ratings and in the SOT-23 package. In addition, TI introduced a family of high-speed, 2 Amp MOSFET drivers last year in the SOT-23 package. The 2A drive capability allows these devices to drive very large loads while the size allows the power supply design to move to a smaller platform. TI also has the TPS760, its first LDO voltage regulator in the SOT-23 package.
TI's PowerPAD™ package is another small outline package, but one that offers additional power dissipation and higher functionality. This package has an exposed thermal pad that can be soldered directly to the printed circuit board to provide extra heatsinking. It has a very small footprint and is compatible with standard automated surface mount assembly processes. And its higher pin count results in higher functionality.
Design Challenge #4: Ability to Support Emerging Standards
In the electronic equipment market, standards for component performance continue to evolve -- requiring more power to be contained in less area. An excellent example of where standards are being used to better define and shape future products is the personal computer industry. The PC industry is governed by not one but several standards. Each of these standards has specifications for power -- such as for microprocessor power supplies -- and for power distribution for PCMCIA and USB peripherals.
TI is a proven leader in the support of these emerging standards. Its microprocessor power supply regulator -- the TPS5210 -- is the first to support the standards for the future 64-bit Merced processor. Its family of power distribution switches for PCMCIA -- the TPS2205, TPS2206 and TPS2211 -- includes both single and dual switches with a serial or parallel interface. TI's family of USB power distribution switches -- the TPS2041/51, TPS2042/52 and TPS2044/54 -- includes single, dual and quad devices that are tailored to meet USB applications and the general power distribution market.
Summary
By providing designers with the power management solutions they need to meet today's design challenges, TI continues to build a position of analog leadership. These solutions provide unique features -- be it size, voltage, or sleep state to name just a very few. With this selection of features, designers can find the right solution for their design with minimal effort.
For more information on TI's offering of power management devices, visit the World Wide Web at  http://www.ti.com/sc/power
# # #
Trademark:
PowerPAD is a trademark of Texas Instruments Incorporated.
|
Related Documentation: