Power control chipset uses fewer capacitors

Semtech has a power control chipset it reckons greatly simplifies design of the latest Pentium4 processor-based motherboards.

Semtech has a power control chipset it reckons greatly simplifies design of the latest Pentium4 processor-based motherboards.

The chipset meets the stringent voltage, current, power-up sequencing, and voltage-tracking requirements for motherboards and their integrated-graphics PC chipset, including those for the Advanced Configuration and Power Interface (ACPI) specification and double-data rate (DDR) memory chips.

Semtech's power control chipset grants designers several advantages over other approaches that rely on either discrete components or competitive chipsets.

Compared with discrete components, the highly integrated power control chipset provides a complete solution that fully meets specifications, takes less space, and saves design time.

And unlike competitive power chipsets, Semtech's highly integrated set of ICs cuts the required number of output capacitors needed to supply the core voltage by using accurate current sensing to meet the load-line specifications.

Another advantage of the power control chipset is its use of built-in charge pumps to accommodate low-cost, widely available N-channel mosfet switches.

Also, the division of functions among the chips in the Power Control chipset optimises the motherboard layout by allowing designers to put each chip close to where it is needed.

Another key feature of the power control chipset is its ability to automatically maintain the required 2:1 ratio between supply voltage (VDDQ) and termination voltage (VTT) for DDR memory chips.

Additional features include programmable delay for the power good signal and across-the-board overcurrent protection.

Among the five different chips included in Semtech's power control chipset are the SC1549 instantly available DC/DC triple linear controller and the SC1112A triple low-dropout regulator controller, both of which are new to Semtech's product portfolio.

The other chips, all of which have previously been introduced, are the SC2434 two- or three-phase current-mode controller, the SC1205H high-speed synchronous power mosfet driver, and the SC1175 dual synchronous controller.

Of these, the SC1549 controller detects the sleep states from the power control chipset's ACPI controller and converts the main power supply's 5V standby voltage to the proper voltages for instantly available operation.

These voltages include 5V dual outputs for USB, 3.3V dual outputs for PCI, and a programmable 1.5 or 3.3V output for AGP.

It's the SC1549's onboard charge pumps that preclude the need for costly P-channel mosfets and enables operation from a single 5V standby voltage.

The SC1549 comes in a TSSOP-20 package.

The SC1112A controller, which includes a 1.2V reference and charge pump, develops the chipset's 1.2V VID and 1.5 VCC logic (including Gunning transceiver logic) voltages.

It comes in a 16-pin SOIC or TSSOP package and features a programmable delay for the power good signal.

The SC2434 controller, which comes in a 20-pin SOIC package, and either one or two SC1205H SO-8-packaged drivers, produce the required core voltage.

Of these, the SC2434 uses input current sensing to guarantee precision phase-to-phase current matching.

The SC1205H drivers feature better than 90% efficiency, fast rise and fall times, 8V gate drive for optimal FET enhancement, ultra-low propagation delay, and 5A peak current drive.

The SC1175 controller, available in a 20-pin SO or SSOP package, supplies the 2.5V supply and 1.25V termination voltages for powering DDR memory chips.

Its features include 300kHz fixed-frequency operation, better than 90% efficiency, a temperature-compensated voltage reference, and the ability to drive all N-channel mosfets.

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