SNVS178G – JANUARY 2002 – REVISED FEBRUARY 2013
Hysteretic PFET Buck Controller
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FEATURES
Easy to Use Control Methodology
No Control Loop Compensation Required
4.5V to 35V Wide Input Range
1.242V to V
IN
Adjustable Output Range
High Efficiency 93%
±1.3% (±2% Over Temp) Internal Reference
100% Duty Cycle
Maximum Operating Frequency > 1MHz
Current Limit Protection
VSSOP-8
DESCRIPTION
The LM3485 is a high efficiency PFET switching
regulator controller that can be used to quickly and
easily develop a small, low cost, switching buck
regulator for a wide range of applications. The
hysteretic control architecture provides for simple
design without any control loop stability concerns
using a wide variety of external components. The
PFET architecture also allows for low component
count as well as ultra-low dropout, 100% duty cycle
operation. Another benefit is high efficiency operation
at light loads without an increase in output ripple.
Current limit protection is provided by measuring the
voltage across the PFET’s R
DS(ON)
, thus eliminating
the need for a sense resistor. The cycle-by-cycle
current limit can be adjusted with a single resistor,
ensuring safe operation over a range of output
currents.
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APPLICATIONS
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Set-Top Box
DSL or Cable Modem
PC/IA
Auto PC
TFT Monitor
Battery Powered Portable Applications
Distributed Power Systems
Always On Power
Typical Application Circuit
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Copyright © 2002–2013, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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