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Slew-rate controller softens the shocks

Edited by the Electronicstalk editorial team Oct 2, 2001

The FDG901D is the first slew-rate control IC from Fairchild Semiconductor.

The FDG901D is the first slew-rate control IC from Fairchild Semiconductor.

It capable of reducing current inrush spike voltage and bus disturbances associated with the turning on and off of capacitive loads in battery applications, such as cell phone handsets, PDAs, wireless telephone handsets, portable POS terminals, portable bar code scanners, and palm PCs.

This new device controls the switching rate of an external mosfet load switch, ensuring a smooth transition between states.

An ideal alternative to existing solutions using N-channel mosfets and passive components, the device enables improved operation over a range of mosfet products while featuring lower parts count, improved reliability, improved use of circuit-board real estate, lower assembly costs, reduced system costs, extended battery life due to reduced leakage currents, and improved stability of the transition states over time.

The FDG901D controls the turn-on of a P-channel mosfet to limit inrush current resulting in less power loss and fewer potentially damaging voltage bus transients due to damaging current spikes.

During turn-on the FDG901D slew rate controller drives a P-channel mosfet's gate using a constant current source, thus providing an accurate and consistent timing of voltage transition states.

For efficient turn-off, the IC quickly pulls up the mosfet's gate.

The flexible design of this unique device offers a choice of three programmed dv/dt states, with settings that have a typical gate-drive current of 805A, 15A and 10nA respectively.

Housed in a small SC70-5 package, the new FDG901D slew rate controller provides all the functionality of traditional current inrush solutions with none of the drawbacks of currently available solutions.

The FDG901D is the first in a family of slew rate control IC devices offering increased functionality over standard discrete devices without the cost normally associated with full power IC technology.