Features and Benefits
- Maintains Constant Frequency at Low Output Currents
- Dual N-Channel MOSFET Synchronous Drive
- Programmable Fixed Frequency (PLL Lockable)
- Wide VIN Range: 3.5V to 36V Operation
- Ultrahigh Efficiency
- Very Low Dropout Operation: 99% Duty Cycle
- Low Dropout, 0.5A Linear Regulator for VPP
- Generation or Low Noise Audio Supply
- Built-In Power-On Reset Timer
- Programmable Soft Start
- Low-Battery Detector
- Remote Output Voltage Sense
- Foldback Current Limiting (Optional)
- Pin Selectable Output Voltage
- 5V Standby Regulator Active in Shutdown: IQ < 200 µA
- Output Voltages from 1.19V to 9V
- Available in 28- and 36-Lead SSOP Packages
The LTC1538-AUX/LTC1539 are dual, synchronous step-down switching regulator controllers which drive external N-channel power MOSFETs in a phase-lockable fixed frequency architecture. The Adaptive PowerTM output stage selectively drives two N-channel MOSFETs at frequencies up to 400kHz while reducing switching losses to maintain high efficiencies at low output currents.
An auxiliary 0.5A linear regulator using an external PNP pass device provides a low noise, low dropout voltage source. A secondary winding feedback control pin (SFB1) guarantees regulation regardless of load on the main output by forcing continuous operation.
A 5V/20mA regulator, internal 1.19V reference and an uncommitted comparator remain active when both controllers are shut down. A power-on reset timer (POR) is included which generates a signal delayed by 65536/fCLK (typ 300ms) after the controller’s output is within 5% of the regulated first voltage. Internal resistive dividers provide pin selectable output voltages with remote sense capability on one of the two outputs.
The operating current levels are user-programmable via external current sense resistors. Wide input supply range allows operation from 3.5V to 30V (36V maximum).
- Notebook and Palmtop Computers, PDAs
- Portable Instruments
- Battery-Operated Devices
- DC Power Distribution Systems
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.