DC/DC Buck Controllers step down 3.3V supplies.

Micrel Semiconductor, Inc. Dec 13, 2001

Press Release Summary:

MIC2183 and MIC2184 convert 3.3V to lower levels, such as 2.5V, 1.8V and 1.5V, for use as auxiliary supply voltages. Both devices have input voltage range of 2.9 to 14V, and built-in high-power output drivers capable of driving large MOSFETs. Switching frequency can be 400kHz or 200kHz, depending on efficiency and noise spectrum requirements of power supply. Both are optimized for low voltage power conversion in telecom and datacom systems.

Original Press Release:

Efficient DC/DC Buck Controllers Step Down 3.3V Supplies

SAN JOSE, Calif. - (July 23, 2001) - Micrel has released two new dc/dc controllers that convert 3.3V voltages to lower voltage levels. The MIC2183 and MIC2184, were designed and developed by Micrel Semiconductor (NASDAQ: MCRL), an industry leader in analog, power management and high-speed communications integrated circuits.

Most of today's communications circuits are powered from high power, 3.3V power supplies. It is a common requirement for the circuits to also need some auxiliary supply voltages, like 2.5V, 1.8V, and 1.5V. The MIC2183/4 provide an ideal solution to efficiently generate high-current supply rails from the main 3.3V supply. Both devices feature an input voltage range of 2.9V to 14V. The MIC2183/4 include built-in, high- power output drivers, capable of driving large MOSFETs that provide large output currents.

The MIC2183 is a synchronous buck controller. It can efficiently step down a 3.3V input to generate output voltages of 2.5V, 1.8V, 1.5V, etc. Its synchronous architecture reduces power loss by replacing a lossy Schottky diode with a low on- resistance MOSFET. The MIC2183, for example, can step down a 3.3V input and achieve 2.5V output at 5A at over 94% efficiency.

The MIC2184 is a buck controller. It uses a Schottky diode instead of a MOSFET on the low side of the converter, saving cost. The MIC2184 solution allows the designer to make cost versus efficiency tradeoffs in applications where efficiency is not as critical.

The switching frequency of the MIC2183/4 can be selected from 400kHz, or 200kHz, depending on the efficiency and noise spectrum requirements of the power supply. The parts can be synchronized up to 600kHz. Many designs require more than one dc/dc controller to be used, therefore the synchronization function helps reduce overall noise.

"The MIC2183 and MIC2184 are optimized for low voltage power conversion required in telecom and datacom systems. Their low input voltage capability saves space by eliminating the need for charge pump biasing circuitry needed with other solutions to work at low voltage levels. Flexible frequency selection and synchronization capabilities allow the MIC2183 and MIC2184 to avoid frequencies in sensitive bands of the communications system, " says Tony Grizelj, Micrel's marketing manager for power products.

The MIC2183/4 have maximum duty cycles of 100%. This feature is beneficial in applications where the input and output voltages are close together, and a large duty cycle is required. The MIC2183BM and MIC2184BM are available in the SO-16 package. They are both priced at $3.50 when purchased in 1,000-piece quantities. Samples are available from stock, and production quantities are stock to 12 weeks ARO. In addition, a QSOP 16 package option will be available September 2001; meaning the MIC2183/4 can be designed into a footprint half the size of a standard narrow-body SO-16 package.

Summary of Features & Applications: MIC2183/4 Low-Voltage DCIDC PWM Controllers
* 2.9V to 14V input voltage range
* >90% efficiency
* 400kHz nominal oscillator frequency
* Frequency divide function allows 200kHz / 400kHz operation
* Frequency sync to 600kHz
* Front edge blanking
* Powerful MOSFET drivers
* 100% max duty cycle
* PWM, current mode control
* Soft start
* 0.5ÂµA shutdown current
* Frequency foldback short circuit protection
* Cycle-by-cycle current limiting
* Adjustable under-voltage lockout
* Precision 1.245V reference output (MIC2184)
* 16-pin narrow body SOIC package Applications
* DC power distribution systems
* 3.3V to 2.5V/1.8V/1.5V conversion
* Wireless modems
* Cable modems
* DSL line cards
* 1-and 2-cell Li Ion battery operated equipment