Controller Generates Multi- and Single-Phase Outputs

Aug 1, 2006 12:00 PM
By David Morrison, Editor, Power Electronics Technology

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The TPS40140 synchronous, PWM controller from Texas Instruments (TI) operates as a standalone device that generates two outputs, or as a two-channel, multiphase controller. Using the device's advanced capabilities, designers are now able to “stack” multiple devices together to create a high-density power supply that can generate up to 320 A of output and support up to 16 phases through interleaved operation.

In applications such as high-density telecom and wireless systems, the TPS40140 significantly increases load-handling capability and simplifies power-system design. For 3G base stations driven by 1-GHz DSPs like TI's TMS320TCI6482, the TPS40140 offers greater energy efficiency, low noise and low power. For data-center servers, the controller enables designers to more easily develop a multiphase power system with high efficiency.

TPS40140's stacking capability permits the power supply to perform automatic phase balancing, which significantly minimizes the ripple current in both the output and input capacitors and allows an overall smaller solution size. Designers may also implement topologies where multiple output rails based on multi- or single-phase output topologies are both synchronized and phase balanced to achieve greater levels of power density and flexibility while maintaining a uniform EMI spectrum of frequencies (see the figure).

In a multicontroller design, the clock synchronization between the master and slave controllers is implemented by configuring a series of 39-kΩ resistors that are connected to the phase select (PHSEL) pins of the controllers (refer to the figure again). The PHSEL pin on the master sources a 20-µA current to the voltage divider formed by the resistors. Each slave controller then senses the voltage across its PHSEL pin and selects the proper delay from the master clock I/O signal (CLKIO) to accomplish phase interleaving. On a given master or slave, the two phases are always 180 degrees out of phase. In addition, the CLKIO signal has either six or eight clocks for each cycle of the switching period.

A current-mode controller, the TPS40140 supports a 2-V to 40-V input range, enabling high-performance operation from a 4.5-V to 15-V source. Outputs range from 0.7 V to 5.8 V. The device offers 0.1% line and load regulation, supported by a ±0.5%, 0.7-V voltage reference and a high-accuracy differential load-sense amplifier.

The controller also features a minimum on-time of 50 ns, which represents an improvement from the 200-ns previously achieved by other TPS40K family members. Consequently, the TPS40140 can convert a 15-V input to a 0.7-V output while switching at 1 MHz. The controller also allows power sharing from different voltage rails.

Supervisory and control features include prebias startup capability, programmable undervoltage lockout, lossless inductor dc resistance or resistor current sensing, independent power-good indicators, separate soft-start controls, synchronization input, programmable overcurrent protection and thermal shutdown. In addition, the TPS40140 controller supports three common sequencing schemes: sequential sequencing, ratio-metric sequencing and simultaneous sequencing.

Available now, the TPS40140 is packaged in a 6-mm × 6-mm, 36-pin QFN. Pricing is $3.30 each in quantities of 1000 units. Software development tools for the TPS40140 will be available in the fourth quarter of 2006 through TI's new Pro series of tools. Evaluation modules, application notes and reference designs are available at www.ti.com/tps40140-pr.