Suitable for portable medical equipment highly integrated power supply IC

The latest "portable" processors require large amounts of high-current, low-voltage track, a typical situation for 1.8V or lower.

In addition to numerous low-voltage Rails, many of these applications also require 3V or 3 .3V rail to give large portable hard drives, memory, and the external logic circuits, I/O power supply. In embedded applications, depending on the current requirement, all connected directly to the processor power supply voltage can be high-efficiency step-down DC/DC or LDO.

Recently, this also requires high power efficiency and high processing performance demand has also been extended to the industrial and medical portable applications.

As most new and feature-rich high-end consumer portable devices, handheld data collection devices, rugged inventory control and tracking equipment, portable gas detector, blood analyzers, portable devices and other EKG portable medical equipment, require similar or even greater power efficiency, and processing power. In addition, these devices must be durable, reliable and sufficient light so that it can be regarded as a "portable".

On portable applications, the main power is large Li-ion polymer battery, the/power may offer is above or below the product 3.3V system power voltage.

Regardless of whether such a "portable" processor whether the system is battery-powered, accompany them to the other complexity including: the need for a specific order on all the power and disconnect the power supply; vision system processing needs, to be able to dynamically increase and lower supply voltage. The System Designer, meet all of the application of the microprocessor and the power requirements of a single integrated solution extremely favourable. Applications must meet these requirements, you will need a highly flexible, programmable and efficient multiple output power supply solution.

Figure 1 LTC3589 simplified block diagram

Buck-boost function of design challenges

Today's feature-rich new electronic system most still need + 3V range voltage rail, for example, car Infotainment System I/O power supply or external devices track.

In the power management IC (PMIC) integrated synchronous buck-boost switches feature, enables cross-2.7 ~ 5.5V entire input voltage range to achieve high efficiency 3.3V adjustment, resulting in a higher operating margin. However, the buck-boost design for high efficiency buck than simple DC/DC converter is much more challenging, especially if the requirements for low noise and good transient response load step, the more so.

Reduce heat, optimizing system efficiency

Many industry standard PMIC with various built-in linear regulator.

However, if you don't use enough copper line wiring, heat sink or good design input/output voltage and output current value of the linear regulator for proper management, linear regulator may have in the PC Board local thermal "hotspots". Or, when the input and output voltage difference is large, or if the output current is large, the switching regulator can provide a more efficient way of buck. Today has a built-in low-voltage μ P and a feature-rich devices, switching regulators for use is widespread. Therefore, for most of the voltage Rails deployment based on the switch mode power supply more and more important. However, output LDO with low noise and high PSRR performance, therefore, must evaluate the tradeoff between the two. In many cases, appropriate IC partition includes two types of regulators.

Today, almost all applications on the system is sensitive to heat.

As processing performance and increases the operating current, replace with switching regulator LDO becomes increasingly important. In a highly integrated power in particular, because a single IC radiates capacity is limited. In addition, depending on the implementation of processing operations, for optimal power needed for many kernel processing track for dynamic modulation. To the higher clock speeds, high power supply voltage is required. Similarly, the processing task less intensive work mode, very low voltage is sufficient. Since the supply current tends to track the input supply voltage, so let the processor to a minimum supply voltage is desirable. To dynamically adjust processor voltage source needs such as I2C this serial port to communicate the changes that have taken place. Today's high-end laptop processor almost all support this feature, however, take advantage of this feature requires an equally flexible and programmable power solutions.

Portable medical and industrial equipment of power management issues

As with many other applications, low-power precision components already make a portable medical equipment.

However, unlike many other different applications, portable medical products in addition to requirements for light weight for easy carrying, generally have higher reliability, uptime and soundness standard. Most of the burden fell on the power system and its components. Medical product must work properly, but depending on the design and the input power requirements, often must be in a variety of seamless handover between the power supply. Must make every effort to protect the device against failure and are able to withstand failures, you must have battery power to work longer hours, and ensure that whenever the existence of effective power, reliable operation.

In addition, the power values with the function and the increase in the number of the voltage Rails.

In addition to distant regions applications maintenance less, can withstand the extreme temperature changes and subject to mechanical vibration or shock will not damage requirements, industrial portable devices and medical devices has many of the same requirements.

In short, the System Designer main challenges including:

● Integrated buck-step-up regulator

● In power consumption and more switching regulator and the highly integrated LDO tradeoffs between

● Integrated dynamic I2C control

• Industrial and medical equipment system of reliable

And robustness requirements

● Solution size and occupy an area of

A simple solution

Past industry PMIC doesn't have enough power to meet these new systems and microprocessors.

Meet the power management IC design limit of any solution must have: a highly integrated, including integrated high current switching regulator and LDO; such as buck-boost regulator and other hard-to-use features widget on key parameters for dynamic I2C control. In addition, a high switching frequency of the device reduces external component dimensions and ceramic capacitors to reduce output ripple.

Facing the new processor power PMIC

LTC3589 is a complete power management solutions, based on the ARM processor and advanced portable microprocessor systems.

The device contains: 3 synchronous step-down DC/DC converter for kernel, memory and SoC track; a synchronous buck-boost-regulator for 2.5 ~ 5V I/O; 3 250mA of LDO regulator for low-noise analog power supply. I2C serial port used to control the pressurizer, output voltage, dynamic voltage scaling and conversion rates, operating mode, and status reports. To the desired order regulator output is connected to the PIN or through I2C port, you can sort on regulators start. Via a button interface, enter the PIN or I2C interface, you can control the system is powered on, power off and reset functions. Voltage monitor and source discharge circuit can be next to ensure a clean before the sequence of power, in addition, the selected voltage regulator can dispense for power button control (for example, memory, and when it must remain in the stop mode is run). LTC3589 to 8 independent axle, the appropriate power value, the dynamic control and ordering support i.MX, PXA and OMAP processors. Other features include VSTB pin etc provided interface signal, the PIN at the same time in as many as four track, to set run and switch between alternate output voltage. The device flat 40 pin 6mm×6mm exposed pad QFN package.

Figure 2 LTC3589 application circuit LDO regulator

Figure 3 LTC3589 step-down switching regulator application circuit

High integration-support for multiple power rail

LTC3589 is a portable microprocessor and peripheral equipment of complete power management solution.

It offers a total of eight voltage rail to give processor core, SDRAM, system memory, PC card, always-on, real-time clock and HDD function components supply. With these voltage rail is an always-on low quiescent current LDO 1.6A 25mA, one and two 1A Buck Regulator, a 1.2A buck-boost-regulator as well as three 250mA of low dropout linear regulator. Supports multiple voltage regulators is highly configurable power sorting capabilities, dynamic voltage conversion DAC output voltage control, a button interface controller, via the I2C interface regulator control as well as a large number of status reports and interrupt output.

LTC3589 internal compensation, constant frequency current-mode step-down switching regulator provides current 1A and 1.6A.

Each order with I2C register Buck Regulator, the buck regulator 2.25MHz or 1.125MHz of switching frequency (including phase) is an independent choice. Power frequency is the default, but contain 2.25MHz edge rate adjustment to reduce EMI. Each buck converter has a dynamic conversion of DAC input datum and external feedback PIN to set the output voltage range. The buck regulator with 3 modes of operation-pulse jump mode, burst mode (Burst Mode) or continuous mode-set with I2C interface. In pulse-skipping mode, the voltage regulator can support 100% duty cycle. Burst mode to work in low output load is conducive to achieving the highest efficiency. Apart from the voltage output set point between dynamic conversion control, forcing the continuous mode also light loads, minimize the output voltage ripple.

Single inductor, 4 switching buck-boost DC/DC voltage-mode converter from 2.5 ~ 5V voltage produced a user programmable output voltage Rails.

The buck-boost-converter using proprietary switching algorithm, above, below or equal to the desired output track input voltage to maintain high efficiency and low noise. Buck-boost error amplifier uses a fixed 0.8V datum, and the output voltage by an external resistor divider set. Burst mode work started by I2C control register. The buck-boost converter, without external compensation components.

Dynamic voltage rail control and other features of I2C control

LTC3589 has high-end portable application processor required I2C control functions, dynamic voltage scaling (Dynamic Voltage Scaling) and optional voltage conversion settings.

In order to make the conversion IC DAC reference works, three LTC3589 step-down switching regulator and linear regulators LDO2 a programmable DAC reference input. Each DAC in 0.3625 ~ 0.75V range are available in accordance with the stepping 12.5mV programming.

You can also order the DAC reference to four optional conversion rate of one and independently in the transition between the two voltage.

Each DAC has two independent output voltage registers, and voltage registers select, conversion rate and start control. You do not have to change for the DAC output and start these regulators.

Figure 4 shows the buck regulator 1, 2, 3 and 4 LDO2 to possible conversion rate in 0.8 ~ 1.2

V conversion, conversion from VSTB pin (grey) started. These values are 8 separate DAC code.

Figure 4 LTC3589 dynamic voltage scaling conversion

Universal I2C serial port used to control the pressurizer, output voltage values, operating mode and status reports.

LTC3589 I2C serial ports on contains 13 used to control each regulator command registers, one that monitors each regulator power supply good status of read-only registers, one used to read the IRQ event causes the read-only registers and an purge IRQ command registers. LTC3589 I2C port support on any of the registers of random address, and you can use multiple START sequence, the order in accordance with any written registers. All registers can be read back to verify the integrity of the software and hardware.