LM34927 Datasheet, PDF (1/17 Pages) Texas Instruments – Integrated Secondary Side Bias Regulator for Isolated DC-DC Converters

LM34927
April 5, 2012
Integrated Secondary Side Bias Regulator for Isolated DC-
DC Converters
General Description
The LM34927 regulator features all of the functions needed
to implement a low cost, efficient, isolated bias regulator. This
high voltage regulator contains two 100V N-Channel MOS-
FET switches - a high-side buck switch and a low-side syn-
chronous switch. The Constant-on-time (COT) control
scheme employed in the LM34927 requires no loop compen-
sation and provides excellent transient response. The regu-
lator operates with an on-time that is inversely proportional to
the input voltage. This feature allows the operating frequency
to remain relatively constant. An intelligent peak current limit
is implemented with integrated sense circuit. Other features
include a programmable input under voltage comparator to
inhibit operation during low-voltage conditions. Protection
features include thermal shutdown and V_CC Undervoltage
Lockout (UVLO). The LM34927 is offered in LLP-8 and
PSOP-8 plastic packages.
Features
■ ^{Wide 9V to 100V Input Range}
■ ^{Integrated 100V, High and Low Side Switches}
■ ^{No Schottky Required}
■ ^{Constant On-Time Control}
■ ^{No Loop Compensation Required}
■ ^{Ultra-Fast Transient Response}
■ ^{Nearly Constant Operating Frequency}
■ ^{Intelligent Peak Current Limit}
■ ^{Adjustable Output Voltage From 1.225V}
■ ^{Precision 2% Feedback Reference}
■ ^{Frequency Adjustable to 1MHz}
■ ^{Adjustable Undervoltage Lockout (UVLO)}
■ ^{Remote Shutdown}
■ ^{Thermal Shutdown}
Packages
■ ^LLP-8
■ ^PSOP-8
Applications
■ ^{Isolated Telecom Bias Supply}
■ ^{Isolated Automotive and Industrial Electronics}
Typical Application
FIGURE 1. Typical Application Schematic
© 2012 Texas Instruments Incorporated 301779 SNVS799
30177901
www.ti.com