Product category:
Power Supply ICs and Controllers
News Release from: Semtech | Subject: SC1538 and SC1548
Edited by the Electronicstalk Editorial
Team on 19 July 2001
Linear FET controllers for space-saving
PSU design
Semtech has a new family of linear FET controllers that enable simple, space-saving design of distributed single and dual power supplies on primary and peripheral circuit boards.
Semtech has a new family of linear FET controllers that enable simple, space-saving design of distributed single and dual power supplies on primary and peripheral circuit boards The highly integrated SC1538 (dual regulator) and SC1548 (single regulator) are linear voltage regulator controllers that together with inexpensive external N-channel FETs can be used to generate well regulated output voltages with overcurrent protection
This article was originally published on Electronicstalk on 16 Jul 2001 at 8.00am (UK)
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The dropout voltage for an application can be met merely by selecting the required FET RDS(ON).
Key applications include instantly available PCs, next-generation computers, network hubs and routers, telecommunications systems and line cards, PC Cards, industrial PCs and DSP-based systems, among others.
The SC1538 is a dual linear FET controller that provides superior voltage regulation characteristics over variations in line, load, and temperature, while dissipating virtually no power.
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The SC1538 controls two separate series pass FETs to provide regulation for two independent supply planes, and is currently available in three versions.
The SC1538CS15/18 is intended for leading-edge microprocessor-based designs, providing a 1.515V power supply, such as used by industry standard GTL+ (gunning transciever logic) and AGP (accelerated graphics port) planes, as well as a 1.818V supply for a chipset I/O or memory termination plane.
The SC1538CS25/25 furnishes two separate 2.525V supplies, appropriate for many clock and memory signal planes, while the SC1538SC12/23 provides 1.2V for AGTL and 2.3V for I/O.
The SC1548 is identical to the SC1538, except it provides only a single linear FET controller.
The SC1548 also consists of three options, including fixed 1.515 and 1.818V versions, as well as a user adjustable (using external resistors) voltage configuration.
As the FETs being controlled are not switching, they need not be located close to the SC1538 or SC1548 devices, enabling them to be placed in any convenient location which simplifies printed circuit board layout.
The new devices provide separate enable inputs for each linear FET controller, and offer overcurrent protection via feedback through external sense inputs.
Under typical conditions, if any output drops below 1V for more than 4ms, the output is shut down.
This overcurrent feature is blanked for approximately 5ms at startup to avoid false triggering due to output capacitor inrush currents.
Other key features of the new devices include: undervoltage lockout;?low quiescent current in shutdown mode;?excellent transient response for superior load and line regulation; and?application currents and dropout voltage (fixed and adjustable outputs) determined by external components.
The SC1538 is available in an 8-pin SOIC package, while the SC1548 comes in a 5-pin SOT-23 package.
The devices are competitively priced at $1.74 each (SC1538) and $1.59 each (SC1548) in 1000 piece OEM quantities.
Devices are available in production quantities immediately.
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