LT3710
Secondary Side
Synchronous Post Regulator
FEATURES
s
s
s
s
s
s
s
s
DESCRIPTIO
Generates a Regulated Auxiliary Output in Isolated
DC/DC Converters
0.8V
±1.5%
Accurate Voltage Reference
Dual N-Channel MOSFET Synchronous Drivers
High Switching Frequency: Up to 500kHz
Programmable Current Limit Protection
Programmable Soft-Start
Automatic Frequency Synchronization
Small 16-Pin Thermally Enhanced TSSOP Package
The LT
®
3710 is a high efficiency step-down switching
regulator intended for auxiliary outputs in single second-
ary winding, multiple output power supplies.
The LT3710 drives dual synchronous N-channel MOSFETs
and achieves high efficiency. With leading edge modula-
tion, it operates well with either primary side peak current
or voltage mode control. It is synchronized to the falling
edge of the transformer secondary winding and can be
used in both single-ended and double-ended isolated
power converter topologies. A high speed operational
amplifier is incorporated to achieve optimum compensa-
tion and fast transient response. A user selectable discon-
tinuous conduction mode improves light load efficiency.
The LT3710 is available in a thermally enhanced TSSOP-16
exposed pad power package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
48V Isolated DC/DC Converters
Multiple Output Supplies
Offline Converters
TYPICAL APPLICATIO
V
IN
36V
TO 72V
L1
V
CC
BIAS
10k
V
DD
V
CC
BOOST
SYNC GBIAS
10pF
LT3710
V
FB
FG
I
SNS
LTC1698
10k
180pF
TG BG
LT3781
SG
0.01µF
C
S
680pF
CSET
TG
0.1µF
SW
ILCOMP BG
SS
BGS
V
FB
PGND
CL
–
CL
+
VA
OUT
3.3k
33nF
2.32k
3.01k
220Ω
Q2
B340A
4700pF
Q1
L2
1.8µH
0.006Ω
4.7µF
CMDSH-3
V
COMP
CG
•
•
•
•
SYNC
OPTODRV
V
C
+
–
V
REF
V
FB
GND
ISOLATION
BOUNDARY
C
OUT2
: POSCAP, 680µF/4V
L2: SUMIDA CEP125-IR8MC-H
Q1, Q2: SILICONIX Si7440DP
PLEASE REFER TO FIGURE 3
IN THE APPLICATIONS SECTION
FOR THE COMPLETE SCHEMATIC
Figure 1. Simplified Single Secondary Winding 3.3V and 1.8V Output Isolated DC/DC Converter
3710f
U
V
OUT1
3.3V
AT 10A
U
U
+
V
OUT2
1.8V
AT 10A
C
OUT2
3710 F01
1
LINER [ LINEAR TECHNOLOGY ]
