Electronic Design

Efficient PWM Controller IC Bound For Notebook Computers

Designers of notebooks and other battery-powered applications on the hunt for ways to simplify design, reduce component count, and lower overall cost should look at a novel pulse-width-modulated (PWM) controller. Among other features, the advanced multi-output voltage SC1404 offers 95% efficiency.

The SC1404 accepts inputs from 6 to 30 V dc. Its two synchronous PWM switching power-supply controllers are preset to generate independent 3.3-V and 5-V supplies. The IC also supplies a 12-V, 200-mA linear regulated output to accommodate the power requirements of many legacy notebook and embedded PC designs.

The two PWM controllers switch out-of-phase to provide ripple cancellation at the input supply, drastically reducing input capacitance filtering requirements. The IC's control loop can also be externally compensated, reducing the amount of output capacitance requirements.

Semtech's proprietary Virtual Current Sense technology provides peak current-mode control. This control is based on a synthetically generated current sense signal that's an order of magnitude larger than the signal generated by conventional current-sensing means.

Quiescent power consumption is 6 mW, standby current is 250 µA, and total supply current in shutdown is 4 µA. The user can select 200-kHz operation (for best efficiency) or 300-kHz operation (for minimal ripple, fast transient response, and/or small output filter component size).

Line and load regulation is 0.08%/V and −0.6%/V, respectively. Other features include overcurrent, overvoltage, and overtemperature protection as well as undervoltage lockout. A 5-V linear regulator can deliver up to 50 mA in standby.

In 1000-unit lots, the SC1404 is priced at $4.05 each for a TSSOP-28 package and $3.95 each for a SSOP-28 package.

Semtech Corp.
(805) 498-2111

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