A synchronous-buck power supply controller from Texas Instruments (TI) can control regulator circuits for high performance processors above 30 Amps of output current and enable more than 90 percent efficiency. This highly integrated device uses a hysteretic controller to deliver superior transient response. It also delivers extremely high levels of initial setpoint accuracy -- ý1 percent over the full operating temperature range. With this announcement, Texas Instruments is first-to-market with a power supply controller designed specifically to meet the demands of the next-generation Merced microprocessor.

"The lower voltages and higher currents of today's Pentium-class processors and future 64-bit Merced processors demand a new generation of power supply controllers," said Les Hodson, System Engineering Manager for TI's Power Management Products. "Our controller, designated the TPS5210, meets the need for high output current and fast transient response while consuming only 120 milliWatts of power. This makes it ideal for leading-edge PC motherboard designs."

Hysteretic Controller Enables Breakneck Transient Response

When output current increases at high rates such as 30 Amps per microsecond, the TPS5210 can recover to the original output value in under 2 microseconds. However, the TPS5210 is "instantaneously in regulation" as the result of an integrated hysteretic control scheme. It works as follows. The designer selects an acceptable window around the reference voltage and programs the TPS5210 using a resistor. The device then compares the output voltage to the programmed window, turning the high-side FET on and off to maintain V_out within the window. Propagation delay from the comparator inputs to the output drives is less than 250 nanoseconds. The user-selectable hysteretic controller and droop compensation in the TPS5210 dramatically reduce overshoot and undershoot caused by load transients.

Highest Integration Currently Available

The TPS5210 features include:

The power demands of the next-generation PCs are not trivial. There is a steady march of operating voltages going lower and lower, with some circuitry operating at 1.8 V (and getting lower still), and most using a mixture of operating voltage levels: all designed to reduce the V-squared component of power dissipation while driving the individual stages at the lowest practical voltage. But those lower voltages are increasing the current demands and, more importantly, the rate of change of currents on the power supplies. Tolerances have to increase in the voltages supplied to the microprocessors and the noise levels on rails has to be tightened up at the same time. And, of course, the PC manufacturer wants the power parts to continue to be the same size, or smaller, and to use less power themselves.

This is the first part to qualify for the Merced (due in mid-2000) and TI considers it important as a roadmap to the technology needed for their own future DSPs; lower currents, same philosophy. The hysteresis is set by two external resistors with V_ref (on-chip bandgap) as the center. The internal low-side and high-side drivers can each handle 2 A, source and sink, while current sensing is by sampling and holding the voltage across the high-side power FETs while they are on -- which requires an external ceramic capacitor. Typical quiescent current with the switching frequency of 200 kHz and a 10.5-V supply is between 3 and 5 mA.

This might not be a part that ships in volume today but it will in another 18 months. Before that time there will undoubtedly be specification changes from Intel but the bigger problems are already solved by this technology and it will be designed in by numerous OEMs before then. The TPS5210 is in production in either a 28-pin SOIC or TI's 28-pin PowerPAD (with a solderable external pad) at $2.25 in 10,000-piece lots.

In addition, an evaluation module for the TPS5210 is also available now.