LT3575_15 Datasheet, PDF (1/24 Pages) Linear Technology – Isolated Flyback Converter without an Opto-Coupler

FEATURES
n _{3V to 40V Input Voltage Range}
n _{2.5A, 60V Integrated NPN Power Switch}
n _{Boundary Mode Operation}
n _{No Transformer Third Winding or}
Optoisolator Required for Regulation
n _{Improved Primary-Side Winding Feedback}
Load Regulation
n _{VOUT Set with Two External Resistors}
n _{BIAS Pin for Internal Bias Supply and Power}
NPN Driver
n _{Programmable Soft-Start}
n _{Programmable Power Switch Current Limit}
n _{Thermally Enhanced 16-Lead TSSOP}
APPLICATIONS
n _{Industrial, Automotive and Medical Isolated}
Power Supplies
LT3575
Isolated Flyback Converter
without an Opto-Coupler
DESCRIPTION
The LT^®3575 is a monolithic switching regulator specific-
ally designed for the isolated flyback topology. No third
winding or optoisolator is required for regulation. The
part senses the isolated output voltage directly from the
primary side flyback waveform. A 2.5A, 60V NPN power
switch is integrated along with all control logic into a
16-lead TSSOP package.
The LT3575 operates with input supply voltages from
3V to 40V, and can deliver output power up to 14W with
no external power switch.The LT3575 utilizes boundary
mode operation to provide a small magnetic solution with
improved load regulation.
The output voltage is easily set with two external resistors
and the transformer turns ratio. Off the shelf transformers
are available for many applications.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and No RSENSE and ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V Isolated Flyback Converter
V_IN
12V TO 24V
10μF
357k
51.1k
V_IN
SHDN/UVLO
0.22μF 1k ^3:1
24μH
2.6μH
TC
R_ILIM
SS
VC
LT3575
R_FB
R_REF
80.6k
SW
GND TEST BIAS
6.04k
28.7k 10k
11.5k
10nF
4.7nF
4.7μF
3575 TA01
V_OUT+
5V, 1.4A
47μF
V_OUT–
Load Regulation
1
V_IN = 24V
0
V_IN = 12V
–1
–2
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
I_OUT (A)
3575 TA01b
3575f
1