LM34925 Datasheet, PDF (1/27 Pages) Texas Instruments – Integrated Secondary-Side Bias Regulator for Isolated DC-DC Converters

Product
Folder
Sample &
Buy
Technical
Documents
Tools &
Software
Support &
Community
Reference
Design
LM34925
SNVS846F – JUNE 2012 – REVISED NOVEMBER 2014
LM34925 Integrated Secondary-Side Bias Regulator for Isolated DC-DC Converters
1 Features
•1 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™
2 Applications
• Isolated Telecom Bias Supply
• Isolated Automotive and Industrial Electronics
3 Description
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
V_CC Undervoltage Lockout (UVLO). The LM34925
device is offered in 8-pin WSON and
8-pin SO PowerPAD plastic packages.
Device Information⁽¹⁾
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LM34925
SO PowerPAD (8)
WSON (8)
4.89 mm × 3.90 mm
4.00 mm × 4.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Schematic
D1
VOUT2
VIN
7.5V-100V
+
C_IN
R_UV2
R_UV1
+
LM34925
N_S
C_OUT2
7
2
V_IN
4 _RON
BST
+
SW ⁸
C_BST
X1
N_P
VOUT1
R_ON
6
3 _UVLO
VCC
FB ⁵
D2
R_FB2
R_r
RTN
1
+
C_VCC
R_FB1
+
C_OUT1
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.