LT3710
1
3710f
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.
n
48V Isolated DC/DC Converters
n
Multiple Output Supplies
n
Offline Converters
, LTC and LT are registered trademarks of Linear Technology Corporation.
n
Generates a Regulated Auxiliary Output in Isolated
DC/DC Converters
n
0.8V – 1.5% Accurate Voltage Reference
n
Dual N-Channel MOSFET Synchronous Drivers
n
High Switching Frequency: Up to 500kHz
n
Programmable Current Limit Protection
n
Programmable Soft-Start
n
Automatic Frequency Synchronization
n
Small 16-Pin Thermally Enhanced TSSOP Package
Figure 1. Simplified Single Secondary Winding 3.3V and 1.8V Output Isolated DC/DC Converter
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
Secondary Side
Synchronous Post Regulator
V
COMP
V
DD
LTC1698
GND
V
FB
CG
FG
I
SNS
SYNC
OPTODRV
V
CC
BIAS
L1 V
OUT1
3.3V
AT 10A
BG
LT3781
SG
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
3710 F01
V
IN
36V
TO 72V
V
REF
V
C
V
FB
TG
••
GBIAS
4.7µF
CMDSH-3
Q1
Q2 B340A
3.01k
2.32k
L2
1.8µH
0.006Ω
V
CC
BOOST
CL
–
CL
+
LT3710
SYNC
TGCSET
ILCOMP
SS
••
–
+
0.1µF
3.3k
33nF
10pF
C
S
680pF
10k
10k
180pF
0.01µF
BGS
PGND
SW
BG
VA
OUT
V
FB
4700pF
V
OUT2
1.8V
AT 10A
C
OUT2
+
220Ω