LINEAR TECHNOLOGY LTC3748 Technical data
48V No-Opto Isolated Applications
EN/UVLO
TC
SS
R
FB
R
REF
V
C
GND
INTV
CC
LT3748
56.2k
2nF
V
IN
22V TO 75V
V
OUT
+
12V
2A
V
OUT
–
V
IN
4:1
412k
15.4k
10µF
3.8µH
60.8µH
100µF
GATE
SENSE
4700pF
4.7µF
6.04k
243k
0.033Ω
10k
LOAD CURRENT (A)
0
11.4
V
OUT
(V)
11.6
11.8
12.0
12.2
12.4
12.6
0.5
1.0
1.5
2.0
VIN = 72V
V
IN
= 48V
V
IN
= 36V
The Transformer is the Only Part Crossing the Isolation Barrier
The LT®3748 is a high input voltage isolated flyback DC/DC controller that does not require an opto-isolator, third winding or signal
transformer for feedback. The output voltage is sensed from the primary-side flyback signal, and is set with two external resistors
and the transformer turns ratio. The LT3748 operates over a 5V to 100V input voltage range, drives an external N-channel power
MOSFET and maintains better than ±5% overall regulation.
Features
n
Input Voltage Range: 5V to 100V
n
No Opto-Coupler Required
n
Primary-Side Winding V
n
V
Set with Two External Resistors
OUT
n
1.9A Onboard Gate Driver
n
Boundary Mode Operation
n
Off-the-Shelf Transformers
n
Only One Part Crossing the Isolation Barrier
n
MSOP-16 with High Voltage Spacing
n
Programmable Soft-Start
Sensing
OUT
Output Load and Line Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
1
3
5
6
7
8
V
IN
EN/UVLO
INTV
CC
GATE
SENSE
GND
16
14
12
11
10
9
R
FB
R
REF
TC
V
C
SS
GND
TOP VIEW
MS PACKAGE
16 (12)-LEAD PLASTIC MSOP
1mm
LT3748 Demo Board
V
C
V
IN
t
SP
NV
OUT
OUTPUT VOLTAGE SENSING AT SWITCH NODE
N-TRANSFORMER
TURNS RATIO
ACTUAL CIRCUIT SIZE: 38mm × 19mm × 9.5mm
The LT3748 is available in an MSOP-16 package with 4 pins
removed for high voltage spacing. The high level of integration,
readily available off-the-shelf transformers and the use of
boundary mode operation results in a simple, clean application
solution.
LT3748 Package Outline
Primary-Side Switch
Node Waveform
Examples of Off-the-Shelf Transformers (See Data Sheet for More Options)
Target Application Supplier Size (W × L × H) (mm) Part Number
20V to 75V → 12V/1A Pulse 18 × 14 × 13 PA2367NL
20V to 75V → 5V/2A Pulse 18 × 14 × 13 PA1260NL
10V to 40V → 10V/2.5A Pulse 29 × 22 × 11.5 PA3177NL
30V to 75V → 12V/1A Wurth 18 × 14 × 13 750311424
30V to 75V → 5V/3A Wurth 18 × 14 × 13 750311423
10V to 40V → 5V/3A Wurth 18 × 14 × 13 750311564
20V to 75V → 12V/2.5A Wurth 29 × 23 × 11.5 750311607
Other Related Flyback Converters and Controllers from Linear Technology
Part Number VIN Range (V) No Opto-Coupler Required Onboard Switch Max Output Power
LT3511 4.5 to 100
LT3512 4.5 to 100
LT3574 3 to 40
LT3573 3 to 40
LT3575 3 to 40
LT3758 5.5 to 100 NA 60W
LT3757 2.9 to 40 NA 60W
√
√
√
√
√
0.24A/150V 2.5W
0.40A/150V 5W
0.65A/60V 3W
1.25A/60V 7W
2.5A/60V 14W
www.linear.com/3748 n 1-800-4-LINEAR
1110
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