LT3710 データシートの表示（PDF） - Linear Technology
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LT3710 Datasheet PDF : 12 Pages
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LT3710
APPLICATIO S I FOR ATIO
forward converter with synchronous rectification. The
primary side controller uses an LT3781, a current mode
2-transistor forward controller with built-in MOSFET driv-
ers. On the secondary side, an LTC1698 is used to provide
the voltage feedback for the 3.3V output, as well as the gate
drive for the synchronous MOSFETs. The error amplifier
output is fed into the optocoupler and then relayed to
LT3781 on the primary side to complete the 3.3V regula-
tion. The 1.8V output is generated by the LT3710 circuit.
A planar transformer PA0191 built by Pulse Engineering is
employed as the power transformer in this design. This
transformer is constructed on a PQ20 core with a nine turn
primary winding, two turn secondary winding and seven
turn auxiliary winding for the LT3781 bias supply. Because
the maximum secondary voltage VSP is about 16V, 30V
MOSFETs are chosen with the consideration that the
secondary voltage overshoot is typically 20% to 30% of
VSP. In this particular design, Si7440DP is selected due to
its low RSD(ON), 30V VDSS rating and its compact and
thermally enhanced PowerPak SO-8 package.
The switching frequency of the circuit is about 230kHz.
1500V input to output isolation is provided. Additional
features of this design include primary side on/off control,
±5% secondary side trimming on the 3.3V output, input
overvoltage protection and undervoltage lockout. The
complete design will mount within a standard half brick PC
board with about half inch height.
SEC
VCCS
1µF
10pF
10k
0.01µF
C37 680pF
10k
180pF
1
5 SYNC BOOST
7 SS
13 VCC
4 CSET
LT3710
14 PGND
6 ILCOMP
17 PGND
VAOUT
10
4.7µF
16V
GBIAS 16
TGATE 2
SW 3
BGATE 15
BGS 9
CL+ 11
CL– 12
VFB
0.01µF
8
CMDSH-3
0.1µF
16V
Si7440DP
10Ω
CMDSH-3 Si7440DP
0.033µF 3.3k
1.8µH
SUMIDA 0.006Ω
CEP125-IR8 1%
B340A
VOUT2
1.8V/10A
+ 680µF + 680µF
4V
4V
POSCAP
POSCAP
3.01k
1%
4700pF
220Ω
330pF
2.32k
1%
3710 F03b
Figure 3b. 36V to 72V DC to 3.3V/10A and 1.8V/10A Dual Output Isolated Power Supply (Part 2 of 2, See Previous Page)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
3710f
11
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