Linear Technology LT8302 Operation

FeaTures
2.8V to 42V Input Voltage Range
n
3.6A, 65V Internal DMOS Power Switch
n
Low Quiescent Current:
n
106µA in Sleep Mode
380µA in Active Mode
Quasi-Resonant Boundary Mode Operation at
n
Heavy Load
Low Ripple Burst Mode
n
Minimum Load < 0.5% (Typ) of Full Output
n
No Transformer Third Winding or Opto-Isolator
n
Required for Output Voltage Regulation
Accurate EN/UVLO Threshold and Hysteresis
n
Internal Compensation and Soft-Start
n
Temperature Compensation for Output Diode
n
Output Short-Circuit Protection
n
Thermally Enhanced 8-Lead SO Package
n
applicaTions
Isolated Automotive, Industrial, Medical Power
n
Supplies
Isolated Auxiliary/Housekeeping Power Supplies
n
Typical applicaTion
2.8V to 32V /5V
IN
V
IN
2.8V TO 32V
V
IN
10µF
EN/UVLO
LT8302
GND
INTV
CC
1µF
Operation at Light Load
®
Isolated Flyback Converter
OUT
3:1
470pF
•
9µH 1µH
39
•
SW
154k
R
10mA TO 1.1A (V
FB
10mA TO 2.0A (V
R
REF
10mA TO 2.9A (V
115k 10k
TC
8302 TA01a
For more information
42V Micropower No-Opto
IN
Isolated Flyback Converter
with 65V/3.6A Switch
DescripTion
The LT 8302 is a monolithic micropower isolated flyback
®
converter. By sampling the isolated output voltage directly
from the primary-side flyback waveform, the part requires
no third winding or opto-isolator for regulation. The output
voltage is programmed with two external resistors and a
third optional temperature compensation resistor. Bound-
ary mode operation provides a small magnetic solution with
excellent load regulation. Low ripple Burst Mode operation
maintains high efficiency at light load while minimizing the
output voltage ripple. A 3.6A, 65V DMOS power switch
is integrated along with all the high voltage circuitry and
control logic into a thermally enhanced 8-lead SO package.
The LT8302 operates from an input voltage range of 2.8V
to 42V and delivers up to 18W of isolated output power.
The high level of integration and the use of boundary
and low ripple burst modes result in a simple to use, low
component count, and high efficiency application solution
for isolated power delivery.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5438499, 7463497, 7471522.
+
V
OUT
5V
220µF
–
V
OUT
= 5V)
IN
= 12V)
IN
= 24V)
IN
www.linear.com/LT8302
LT8302
Efficiency vs Load Current
90
FRONT PAGE APPLICATION
85
80
75
70
V
65
V
V
60
0 0.5 1.0 1.5 2.0
LOAD CURRENT (A)
= 5V
IN
= 12V
IN
= 24V
IN
2.5 3.0
8302 TA01b
8302fb
1