Step-Down Regulator features 0.08 ohm bypass MOSFET.
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Press Release Summary:
Model LTC3408 synchronous, 1.5 MHz buck regulator uses constant frequency, current mode architecture, which operates from input voltage range of 2.5-5 V. Integrated bypass MOSFET can deliver up to 600 mA of continuous output current from tiny 8-lead DFN package. Output can be dynamically programmed from 0.3-3.5 V. At output voltages above 3.6 V, internal bypass P-Channel MOSFET transistor connects VOUT directly to VBATTERY with dropout of less than 50 mV.
Original Press Release:
Synchronous Step-Down Regulator with 0.08 Ohm Integrated Bypass MOSFET Increases Battery Life in CDMA Cellular Phones
MILPITAS, CA - October 30, 2003 - Linear Technology announces the LTC3408, a high efficiency, 1.5MHz, synchronous buck regulator with an integrated bypass MOSFET that can deliver up to 600mA of continuous output current from a tiny 8-lead DFN package. The on-chip bypass MOSFET has an RDSON of only 0.08 ohm, minimizing power loss in the bypass mode. The LTC3408 uses a constant frequency, current mode architecture, which operates from an input voltage range of 2.5V to 5V, making it ideal for single cell Li-Ion cellular applications. The output can be dynamically programmed from 0.3V to 3.5V to optimize the efficiency of CDMA and WCDMA power amplifiers, increasing battery life. At output voltages above 3.6V, an internal bypass P-Channel MOSFET transistor connects VOUT directly to VBATTERY with a dropout of less than a 50mV (at 600mA), minimizing power loss through the inductor. Its 1.5MHz switching frequency allows utilization of tiny, low cost capacitors and inductors less than 1mm in height. The combination of tiny externals and a 3x3mm DFN package makes the LTC3408 optimal for space-constrained cellular phones.
The LTC3408's dynamic output adjustability feature enables it to constantly optimize the RF Power Amplifier (PA) supply requirements, which continually change depending on the proximity of the nearest base station and its mode of transfer (voice or data). The internal P-Channel MOSFET bypass transistor enables the LTC3408 to connect the PA directly to the battery for high power transmission modes that require voltages above 3.6V while maintaining maximum efficiency. During lower power transmission, the LTC3408 regulates the PA's supply voltage to a lower level to further improve efficiency, while the forced continuous mode enables fast VOUT response to the controlling input. Furthermore, this regulator is stable with ceramic capacitors, achieving very low output voltage ripple. For cellular applications that require bypass capability, moderate output current and high efficiency from a very small form factor, the LTC3408 is an ideal solution.
The LTC3408 is available from stock in an 8-lead DFN package. Pricing starts at $2.15 each for 1,000-piece quantities.
Summary of Features: LTC3408
600mA Output Current
High Efficiency: Up to 96%
Integrated 0.08 ohm Bypass Transistor for VOUT>3.6V
Dynamically Adjustable Output from 0.3V to 3.5V
1.5MHz Fixed Switching Frequency
2.5V to 5V Input Voltage Range
Stable with All Ceramic Capacitors
Low Dropout Operation: 100% Duty Cycle
Selectable Automatic Burst Mode® or Forced Continuous Operation
Very Low Quiescent Current: Only 20uA
Low Shutdown Current <1uA
8-Lead DFN Package (3mm x 3mm x 0.8mm)
Company Background
Linear Technology Corporation was founded in 1981 as a manufacturer of high performance linear integrated circuits. Linear Technology products include operational, instrumentation and audio amplifiers; voltage regulators,power management devices, DC-DC converters and voltage references; comparators; monolithic filters; communications interface circuits; one-chip data acquisition sub-systems; pulse-width modulators and sample-and-hold devices; and high frequencydevices. Applications for Linear Technology's high performance circuits include wireless and broadband telecommunications infrastructure, cellular telephones, networking products and satellite systems, notebook and desk top computers, computer peripherals, video/multimedia, industrial and medical instrumentation, automotive electronics, factory automation, process control, military and space systems, and high-end consumer products including digital cameras, MP3 players and other electronic products.
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Note: LT, AND LTC are registered trademarks of Linear Technology Corp.
