Three new families of power distribution switches announced by Texas Instruments (TI) offer designers new options for general system power segmentation and Universal Serial Bus (USB) power distribution applications. These devices allow designers to address user demands for improved battery life, reduced system power consumption and greater reliability in an ever-increasing array of electronic systems.

"TI is expanding its power distribution switch offering to address a wide range of needs in the general-purpose, mass-market arena, in addition to the USB and PCMCIA market segments where we have been participating," said Jonathan Bearfield, power supply systems engineer at TI. "For example, non-stop servers demand that systems allow boards to be inserted or removed while power is applied. This is driving widespread implementation of hot-swap capability that translates to increased system ęup-time.ę Additionally, the need to improve battery life and support partial system shut downs during idle periods or during system failures are spurring expanded use of power segmentation techniques."

Options Make Designeręs Job Easier

Applications needing fast response to failure modes and over-current protection or digital control/response are well-served by TIęs three new power switch families, designated the TPS201XA, TPS202X and TPS203X. Multiple current ratings, a choice of positive- or negative-enable logic levels and the option of having an over-current (OC) signal give designers a variety of ways to implement reduced power consumption schemes, system failure protection and hot swap capability for a wide range of system designs.

Segmentation reduces power consumption and enhances system maintainability

All three families are general-purpose power distribution switches that can implement power segmentation schemes for personal computers, servers, notebook computers, digital cameras and many other electronic systems. Segmentation is used to reduce power consumption by shutting down blocks of circuitry in battery-powered applications, thus extending battery life. Segmentation also allows line-powered systems to reduce energy consumption by putting power-hungry portions of the system in a "sleep" mode until needed. The TPS202X and TPS203X series are also excellent solutions for ganged operation in USB applications.

These TI switches all have a low r_DS(on)of 50 mohm maximum, which reduces the power lost in the switch itself and extends the operating range of the system. Additionally, these switches feature a 45ęsec typical over-current response time to reduce the risk of system damage in a short circuit situation.

The TPS201XA devices are active-low logic without an OC pin for applications that do not require this capability. The TPS202X family is active-low logic and the TPS203X family is active-high logic; these families both have an OC pin to provide a status signal to the controller in systems that require this feature.

Additionally, the three families offer continuous operating currents from 0.2 amps to 2.0 amps with typical current limits ranging from .3 amps to 3.0 amps, respectively, depending on the device type. All device-enable pins are compatible with both 3.0 V and 5.0 V logic levels. The range of output currents and enable logic levels gives designers the ability to tailor the operating characteristics of the power distribution system to the specific design.

Complete Power Distribution Switch Offering

TIęs USB power distribution switches are true, single-chip solutions. TI has recently expanded this offering by introducing new devices in its existing two families of USB switches. These new parts are the TPS2045/46/47/48 and TPS2055/56/57/58 single, dual, triple and quad 200 ma USB power distribution switches. They complement previously announced 500 ma versions.

TI is being really customer-oriented in the way that they are  working to provide more parts to groups of users who are already customers. With TI dominating the PCMCIA market it is a natural to try and get more of their solutions into those laptops: preaching to the at least-partially-converted. Power segmentation, either within a single box or between complete operating units, is becoming an important topic. This is particularly because of the much higher current demands of all PCs and especially in the laptop arena where the manufacturer wants battery life to get longer, not shorter!

Hot swapping is also extremely important and switches, protection devices, over-current detection are all in vogue; whereas some semiconductor vendors have gone the route of specialist parts with on-chip MOSFETs -- with wonderfully sophisticated thinking of fault conditions, timing, etc -- others, such as TI adopt the switch approach; this in many ways allows for some rather interesting designs to be built around the switches, the price of which are extremely attractive.