Product category:
Power Supply ICs and Controllers
News Release from: Semtech | Subject: SC1403
Edited by the Electronicstalk Editorial
Team on 25 November 2002
PWM controller makes for simple laptop
supplies
The SC1403 is a multiple-output PWM controller employing Semtech's proprietary Virtual Current Sense technology.
The SC1403 is a multiple-output PWM controller employing Semtech's proprietary Virtual Current Sense technology This product provides important features that simplify design and reduce total system cost, while also delivering the high efficiency required by today's battery-powered notebook PC applications
This article was originally published on Electronicstalk on 16 Jul 2001 at 8.00am (UK)
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The SC1403 is designed to operate from a 6 to 30V supply, making it ideal for operation from either an AC adapter or battery pack.
The SC1403 implements two high efficiency, synchronous power supply controllers preset to generate the 3.3 and 5V supply voltages typically required in a notebook PC.
These outputs can also be adjusted between 2.5 and 5.5V.
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Two key features are incorporated into the SC1403 that help reduce system cost.
The switching power supply controllers operate 180 degrees out-of-phase, providing ripple cancellation at the input supply.
This enables designers to employ as little as one-half of the input capacitance required by competitive products that do not offer out-of-phase operation.
Also, this device offers external compensation capability for each switcher.
Such capability allows a designer to optimise the output filter for voltage ripple and transient response while guaranteeing stable operation.
Other products on the market enforce output capacitor-ESR value constraints to provide stability.
With external compensation, there are no such restrictions; designers have full flexibility to optimise their designs for performance, cost or both.
A significant benefit of Semtech's Virtual Current Sense technology is its ability to enhance control loop stability.
This enables fixed frequency operation over a wide range of output filter components and virtually eliminates the jitter seen in most fixed-frequency PWMs.
Virtual Current Sense, combined with external compensation capability, reduces development risk by removing layout sensitivity from the design.
"The SC1403 provides system and power-supply designers with an unrivaled combination of options and performance from a PWM controller designed for mobile applications", stated Eddie Yeow, Director of Portable Power Management for Semtech.
"We are proud to offer products that not only help customers reduce development risks and system costs but maximise their productivity and time to market as well".
Several features are offered to maximise battery life in notebook PCs, including very low quiescent power consumption - typically 6mW.
In standby mode, quiescent current is reduced to typically 180uA.
In shutdown, the total supply current is typically 4uA.
When the load current falls below an externally programmable threshold, the switcher operates as a hysteretic controller in discontinuous mode, eliminating unnecessary switching cycles and therefore improving light-load efficiency.
The device offers greater than 1A typical gate drive for fast mosfet switching, reducing switching losses.
The drivers also support use of the latest low-on-resistance mosfets optimised for mobile applications, helping to reduce conduction losses.
Other features include excellent line (0.05%/V) and load (-0.4%) regulation; overcurrent, overvoltage and overtemperature protection; undervoltage lockout; and a 5V linear regulator capable of delivering up to 50mA in standby mode.
The SC1403 is rated for operation over the industrial temperature range of -40 to +85C.
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