One chip generates both mobile Pentium supplies

Edited by the Electronicstalk editorial team Apr 9, 2002

Semtech reckons its SC1474 dual-phase power supply controller is the industry's first single-chip controller to supply both Vcore and VID voltages for the latest Mobile Intel Pentium 4 processors.

Semtech reckons its SC1474 dual-phase power supply controller is the industry's first fully-integrated single-chip controller to supply both Vcore and VID voltages for the latest Mobile Intel Pentium 4 processors.

Replete with advanced power saving, space conserving, and design enhancing features, the SC1474 multiphase controller delivers the 0.600 to 1.750V core voltage at up to 40A, and the 1.2V, 300mA VID power to run Intel's newest Pentium 4 processors for notebook computers.

By comparison, competing products require as many as five chips to supply the Vcore and VID rails.

"As the first single-chip answer to the Vcore and VID requirements of Intel's Mobile Pentium 4 processors, the SC1474 offers a compelling list of features that no laptop computer designer can afford to ignore", said Eddie Yeow, Director of Portable Power Management Products at Semtech.

"The SC1474 embodies the best of Semtech's proven expertise in multiphase power controllers, giving designers the breathing room they need for working under tight space and power budgets".

Among the SC1474's many power saving features for stretching battery life is its compliance with the Intel Mobile Voltage Positioning (IMVP-III) specification and the enhanced Intel SpeedStep technology.

As load current increases, IMVP linearly lowers the core voltage to an optimum point within its tolerance window.

Besides saving power, IMVP improves the supply's margin for load transients, reducing bulk capacitance requirements.

SpeedStep technology cuts both the core voltage and clock rate when under battery power, restoring both when power is supplied by an AC power source (performance mode).

The SC1474 automatically detects changes in the VID and adjusts the core voltage accordingly for battery or performance mode operation.

SpeedStep is further enhanced by implementing a "deeper sleep" low voltage state that dramatically reduces power when the CPU is idle.

The SC1474 also features an automatic "power save" mode to maximise efficiency under light loads by preventing negative current flow in the low-side mosfet.

This feature is particularly important for extending battery life since the processor can spend as much as 60 to 70% of the time operating in a low power state.

The SC1474 harnesses its multiphase switching-regulator topology to deliver up to 40A at the required core voltage, which is set by a 5bit DAC accurate to 0.85%.

The dynamic current-sharing feature automatically balances the average current in each phase, eliminating hot spots caused by mismatched trace impedance and component tolerance variations.

This key feature helps the designer successfully deal with challenging layout constraints.

To further simplify design, the two phases operate 180 degrees apart from each other, helping to cancel input ripple and, therefore reduce the required input capacitance.

Other advantages of multiphase operation include high efficiency with a minimum of external components, smaller inductors, fewer input and output capacitors, and tight regulation at the point of load for high-current, high-transient applications.

Yet another key feature of the controller is its use of hysteretic regulation.

This approach does away with the error amplifier needed in conventional regulators.

This eliminates time lags, allowing the SC1474 to deliver superior transient response and greater stability regardless of the equivalent series resistance of the output capacitors.

A linear regulator controller built into the SC1474 delivers the VID's 1.2V, 300mA power.

Use of an external pass transistor supports future requirements up to 600mA.

By integrating Semtech's SmartDriver technology, the SC1474 precludes the need for external mosfet drivers, further reducing cost, space, and component count.

Other features of the SC1474 include programmable soft-start operation, an open-drain power good flag with blanking during VID changes, and an enable input.

In addition, the SC1474 which is protected against thermal overloads and Vcore overvoltage, has a programmable current limiting feature that shuts the chip down after 32 overcurrent pulses, and sports an undervoltage lockout feature on all VCC inputs.

(This was Electronicstalk's Top Story on 8 April 2002).