7.5-100V Wide Vin, 100mA Integrated Secondary Bias Regulator for Isolated DC/DC Converters


Product details


Vin (Min) (V) 9 Vin (Max) (V) 100 Switching frequency (Max) (kHz) 1000 Soft start None Features Adjustable UVLO, Enable Operating temperature range (C) -40 to 125 Iout (A) 0.1 Product type Converter (Integrated switch) Topology Buck, Flybuck open-in-new Find other Flybuck converters

Package | Pins | Size

HSOIC (DDA) 8 19 mm² 4.9 x 3.9 WSON (NGU) 8 16 mm² 4 x 4 open-in-new Find other Flybuck converters


  • Wide 7.5-V to 100-V Input Range
  • Integrated 100-mA High-Side,
    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 1.225 V
  • Precision 2% Feedback Reference
  • Frequency Adjustable to 1 MHz
  • Adjustable Undervoltage Lockout (UVLO)
  • Remote Shutdown
  • Thermal Shutdown
  • Packages:
    • 8-Pin WSON
    • 8-Pin SO PowerPAD™

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The LM34925 regulator features all of the functions needed to implement a low cost, efficient, isolated bias regulator. This high voltage regulator contains two 100-V N-Channel MOSFET switches: a high-side buck switch and a low-side synchronous switch. The constant-on-time (COT) control scheme employed in the LM34925 device requires no loop compensation and provides excellent transient response. The regulator 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 VCC undervoltage lockout (UVLO). The LM34925 device is offered in 8-pin WSON and
8-pin SO PowerPAD plastic packages.

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Technical documentation

= Top documentation for this product selected by TI
No results found. Please clear your search and try again. View all 8
Type Title Date
* Datasheet LM34925 Integrated Secondary-Side Bias Regulator for Isolated DC-DC Converters datasheet (Rev. G) Nov. 20, 2017
Selection guides Power Management Guide 2018 (Rev. R) Jun. 25, 2018
Application notes Fly-Buck(TM) converter provides EMC and isolation in PLC applications Jan. 29, 2015
Application notes AN-2292 Designing an Isolated Buck (Fly-Buck) Converter (Rev. C) Dec. 17, 2014
Technical articles Powering Bipolar Rails with Wide-VIN Fly-Buck Converter Dec. 09, 2014
User guides AN-2204 LM5017 Isolated Supply Evaluation Board (Rev. B) Aug. 13, 2013
Application notes AN-2292 Designing an Isolated Buck (Fly-buck) Converter (Rev. B) May 06, 2013
User guides LM34925 Isolated Evaluation Board (Rev. A) Apr. 23, 2013

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Hardware development

document-generic User guide
The LM34925EVAL evaluation board facilitates evaluation of the LM34925 100V, 100mA Constant On-Time Synchronous Buck Regulator. An isolated bias supply is implemented in this evaluation board with the LM34925 the Constant On-Time regulator. The LM34925 regulator integrates both the high and low side (...)
  • Input Voltage Range: 20V to 100V
  • Primary Output Voltage: 10V
  • Secondary (Isolated) Output Voltage: 9.5V
  • Maximum Load Current (Primary and Secondary): 100mA
  • Maximum Power Output: 1W

Design tools & simulation

SNVM163A.ZIP (34 KB) - PSpice Model
SNVM375.TSC (192 KB) - TINA-TI Reference Design
SNVM376.ZIP (10 KB) - TINA-TI Spice Model
SNVM980.ZIP (2 KB) - PSpice Model
Fly-Buck and Flyback Topology Selector
FLYBUCK-FLYBACK-DESIGN-CALC This tool helps a power supply engineer to select the right isolated DC-DC topology based on the specifications. Depending on the topology chosen, the calculator also recommends the right IC for the design.
  • Features isolated topologies like Fly-Buck™, Fly-Buck-Boost, DCM and CCM Flyback
  • Capability to design up to 6 isolated outputs
  • Recommends ICs for desired application design
  • Incorporates loop compensation in designs
  • Compares efficiency, external component count and transformer currents for every topology (...)

Reference designs

Low-Power Isolated Supply, Input range: 36V to 75V, Output: 10V @ 120mA, LM5017
PMP7798 Based on the Wide VIN COT Sync Buck regulator LM5017, this FlyBuck circuit provides excellent regulation for two isolated outputs and one non-isolated output. Compared with a conventional Flyback circuit, this design features a smaller board size and minimized BOM without the need for an (...)
document-generic Schematic document-generic User guide

CAD/CAE symbols

Package Pins Download
SO PowerPAD (DDA) 8 View options
WSON (NGU) 8 View options

Ordering & quality

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