Multiphase converters

Save to MyST. Product selector. CAD Resources. All resource types Minify. Technical Literature Databrief 4 Technical Note 2. Databrief 4. Technical Note 2. All resource types. Latest update. All dates. Telemetry output from digital controller sends key parameters for GUI display Power In, Power Out, Vin, Vout, Temperature Embedded non-volatile memory stores configuration parameters and enables Black Box Recorder functionality Auto-tuning compensation network simplifies application evaluation of the devices and compensates for drift due to system aging.

Featured Videos. See All. Watch the video 90 seconds. Much of the progress in this area can be traced to gains made in power conversion technology, particularly improvements in power ICs and power semiconductors. In general, these components contribute to enhancing power supply performance by permitting increased switching frequencies with minimal impact on power-conversion efficiency. This is made possible by reducing switching and on-state losses thereby increasing efficiency while allowing for the efficient removal of heat.

However, the migration to lower output voltages places more pressure on these factors, which in turn, creates significant design challenges. Multiphase Topology Multiphase operation is a general term for conversion topologies where a single input is processed by two or more converters, where the converters are run synchronously with each other but in different, locked phases.

This approach reduces the input ripple current, the output ripple voltage and the overall RFI radio frequency interference signature, while allowing high current single outputs, or multiple lower current outputs with fully regulated output voltages. It also allows smaller external components to be used, producing a higher efficiency converter and also providing the added benefit of improved thermal management with less cooling.

Multiphase topologies can be configured as step-down buck , step-up boost and even as a forward converter, although generally the buck regulator is the more prevalent application. At higher power levels, scalable multiphase controllers reduce the size and cost of capacitors and inductors using input and output ripple current cancellation caused by interleaving the clock signals of several paralleled power stages.

Multiphase converters help minimize the external component count and simplify the complete power supply design by integrating PWM pulse width modulation current mode controllers, true remote sensing, selectable phasing control, inherent current sharing capability, high current MOSFET drivers plus overvoltage and overcurrent protection features. The resulting manufacturing simplicity not only helps improve power supply reliability, but it is also scalable.

Such systems can be expanded up to 12 phases for high current outputs as high as A. The circuit in Figure 1 shows a typical LTC application schematic for developing a 1.

The circuit in Figure 2 shows a typical LTC application schematic for developing a 1. The onboard differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling high accuracy regulation independent of IR losses in trace runs, vias and interconnects.

The output current is sensed, monitoring the voltage drop across the output inductor DCR for highest efficiency or by using a sense resistor. This has made them popular in many high current buck step-down applications, especially where space is a concern.

This 4-phase synchronous boost converter can deliver over 12W of power in a smaller size, with higher efficiency and lower output ripple than is achievable with a comparable single-phase boost converter. The LTC can startup with as little as 1V, and operate with inputs up to 4. The output voltage range is 2. The high frequency up to 8MHz 4-phase architecture allows the use of small, low cost inductors rather than a single large, bulky inductor, and requires much less output filter capacitance than the equivalent single-phase circuit.

This is ideal for space-constrained boards, Point-of-Load regulators, and portable devices that demand the use of low-profile components.

Figure 1 shows the size difference between a typical single inductor that would be required to handle this current, and the inductors that could be used in a 4-phase design.

Figure 1 also compares the output capacitors required to achieve the same output ripple voltage in single-phase and 4-phase applications.

Table 1 shows specifications for the inductors pictured in Figure 1—not only are the four small inductors much thinner, but they also have a lower combined DC resistance for improved efficiency. Figure 1. How does a multiphase boost converter improve on its single phase counterpart? First of all, a multiphase topology saves space and simplifies layout by removing bulky, hard-to-place components and replacing them with easier-to-fit, low profile components. Inductor and output capacitor size comparison of single-phase and 4-phase circuits.

Designing a converter using the LTC is no different than designing a traditional single phase boost converter. All the power switches are internal, so the 4-phase operation is transparent. Current limit and switching frequency for all four phases are each programmed by a single resistor, as in single phase designs. Setting the output voltage and compensating the loop are also no different than in other familiar designs.

Each of the four phases has an NMOS and a PMOS power switch, and controls its own inductor current using a peak current mode control loop, consisting of a current comparator with adaptive slope compensation and a reverse current comparator for discontinuous mode operation. In discontinuous mode, an internal resistor is placed across the inductor when the synchronous rectifier turns off, damping any high frequency ringing. A single error amplifier is used for all four phases, and controls the peak current required to maintain regulation.

Soft-start time is set by the C SS capacitor, which ramps the current limit up to its final value during startup. These are typically size parts. The pinout of the LTC lends itself to a tight symmetrical layout of the power components. With the 4-phase architecture, low output voltage ripple is achieved using only the four small ceramic capacitors, even at load currents of 2A or more.

An optional bulk capacitor on V OUT can be added to improve transient response with dynamic loads.