LM34925_14 Datasheet, PDF (1/26 Pages) Texas Instruments – Integrated Secondary Side Bias Regulator for Isolated DC-DC Converters

LM34925
www.ti.com
SNVS846E – JUNE 2012 – REVISED DECEMBER 2013
Integrated Secondary Side Bias Regulator for Isolated DC-DC Converters
Check for Samples: LM34925
FEATURES
1
•2 Wide 7.5 V to 100 V Input Range
• Integrated 100 V, 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 1.225 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
APPLICATIONS
• Isolated Telecom Bias Supply
• Isolated Automotive and Industrial Electronics
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 100V 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 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 is offered in 8-pin
WSON and 8-pin SO PowerPAD plastic packages.
Typical Application
VIN
7.5V-100V
+
C_IN
R_UV2
R_UV1
D1
VOUT2
+
LM34925
N_S
C_OUT2
7
2
V_IN
4 _RON
BST
+
8 ^CBST
SW
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
Figure 1. Typical Application Schematic
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
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.
Copyright © 2012–2013, Texas Instruments Incorporated