LT8302
42V
IN
Micropower No-Opto
Isolated Flyback Converter
with 65V/3.6A Switch
FeaTures
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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.
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2.8V to 42V Input Voltage Range
3.6A, 65V Internal DMOS Power Switch
Low Quiescent Current:
106µA in Sleep Mode
380µA in Active Mode
Quasi-Resonant Boundary Mode Operation at
Heavy Load
Low Ripple Burst Mode
®
Operation at Light Load
Minimum Load < 0.5% (Typ) of Full Output
No Transformer Third Winding or Opto-Isolator
Required for Output Voltage Regulation
Accurate EN/UVLO Threshold and Hysteresis
Internal Compensation and Soft-Start
Temperature Compensation for Output Diode
Output Short-Circuit Protection
Thermally Enhanced 8-Lead SO Package
applicaTions
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Isolated Automotive, Industrial, Medical Power
Supplies
Isolated Auxiliary/Housekeeping Power Supplies
Typical applicaTion
2.8V to 32V
IN
/5V
OUT
Isolated Flyback Converter
V
IN
2.8V TO 32V
V
IN
EN/UVLO
LT8302
GND
1µF
INTV
CC
R
FB
R
REF
115k
TC
10k
8302 TA01a
Efficiency vs Load Current
V
OUT+
5V
90
85
EFFICIENCY (%)
80
75
70
65
60
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
0
0.5
2.0
1.5
1.0
LOAD CURRENT (A)
2.5
3.0
FRONT PAGE APPLICATION
470pF
10µF
39
SW
154k
9µH
3:1
•
1µH
220µF
V
OUT–
•
10mA TO 1.1A (V
IN
= 5V)
10mA TO 2.0A (V
IN
= 12V)
10mA TO 2.9A (V
IN
= 24V)
8302 TA01b
8302fa
For more information
www.linear.com/LT8302
1
LT8302
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
EN/UVLO 1
INTV
CC
2
V
IN
3
GND 4
9
GND
8
7
6
5
TC
R
REF
R
FB
SW
SW (Note 2) ..............................................................65V
V
IN
............................................................................42V
EN/UVLO....................................................................V
IN
R
FB
........................................................V
IN
– 0.5V to V
IN
Current Into R
FB
....................................................200µA
INTV
CC
, R
REF
, TC.........................................................4V
Operating Junction Temperature Range (Notes 3, 4)
LT8302E, LT8302I.............................. –40°C to 125°C
LT8302H ............................................ –40°C to 150°C
LT8302MP ......................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
S8E PACKAGE
8-LEAD PLASTIC SO
θ
JA
= 33°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LT8302ES8E#PBF
LT8302IS8E#PBF
LT8302HS8E#PBF
LT8302MPS8E#PBF
TAPE AND REEL
LT8302ES8E#TRPBF
LT8302IS8E#TRPBF
LT8302HS8E#TRPBF
LT8302MPS8E#TRPBF
PART MARKING
8302
8302
8302
8302
PACKAGE DESCRIPTION
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
2
8302fa
For more information
www.linear.com/LT8302
LT8302
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
EN/UVLO
= V
IN
, C
INTVCC
= 1µF to GND, unless otherwise noted.
SYMBOL
V
IN
I
Q
PARAMETER
V
IN
Voltage Range
V
IN
Quiescent Current
V
EN/UVLO
= 0.3V
V
EN/UVLO
= 1.1V
Sleep Mode (Switch Off)
Active Mode (Switch On)
For Lowest Off I
Q
Falling
V
EN/UVLO
= 0.3V
V
EN/UVLO
= 1.1V
V
EN/UVLO
= 1.3V
I
INTVCC
= 0mA to 10mA
V
INTVCC
= 2.8V
Falling
I
RFB
= 75µA to 125µA
l
l
l
elecTrical characTerisTics
CONDITIONS
l
MIN
2.8
TYP
0.5
53
106
380
MAX
42
2
UNIT
V
µA
µA
µA
µA
V
V
mV
µA
µA
µA
V
mA
V
mV
mV
V
%/V
V
µA
µA
kHz
ns
µs
EN/UVLO Shutdown Threshold
EN/UVLO Enable Threshold
EN/UVLO Enable Hysteresis
I
HYS
V
INTVCC
I
INTVCC
EN/UVLO Hysteresis Current
0.3
1.178
–0.1
2.3
–0.1
2.85
10
2.39
–50
0.98
–0.01
12
11.3
0.75
1.214
14
0
2.5
0
3
13
2.47
105
50
1.00
0
1.00
15
–200
12
160
170
1.02
0.01
18
12.7
0.1
2.7
0.1
3.1
16
2.55
1.250
INTV
CC
Regulation Voltage
INTV
CC
Current Limit
INTV
CC
UVLO Threshold
INTV
CC
UVLO Hysteresis
(R
FB
– V
IN
) Voltage
R
REF
Regulation Voltage
R
REF
Regulation Voltage Line Regulation
2.8V ≤ V
IN
≤ 42V
V
TC
= 1.2V
V
TC
= 0.8V
V
TC
I
TC
f
MIN
t
ON(MIN)
t
OFF(MAX)
I
SW(MAX)
I
SW(MIN)
R
DS(ON)
I
LKG
t
SS
TC Pin Voltage
TC Pin Current
Minimum Switching Frequency
Minimum Switch-On Time
Maximum Switch-Off Time
Maximum Switch Current Limit
Minimum Switch Current Limit
Switch On-Resistance
Switch Leakage Current
Soft-Start Timer
I
SW
= 1.5A
V
SW
= 65V
Backup Timer
3.6
0.78
4.5
0.87
80
0.1
11
5.4
0.96
0.5
A
A
mΩ
µA
ms
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The SW pin is rated to 65V for transients. Depending on the
leakage inductance voltage spike, operating waveforms of the SW pin
should be derated to keep the flyback voltage spike below 65V as shown
in Figure 5.
Note 3:
The LT8302E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT8302I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT8302H is guaranteed over the full –40°C to
150°C operating junction temperature range. The LT8302MP is guaranteed
over the full –55°C to 150°C operating junction temperature range. High
junction temperatures degrade operating lifetimes. Operating lifetime is
derated at junction temperature greater than 125°C.
Note 4:
The LT8302 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
8302fa
For more information
www.linear.com/LT8302
3
LT8302
Typical perForMance characTerisTics
Output Load and Line Regulation
5.20
5.15
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.10
5.05
5.00
4.95
4.90
4.85
4.80
0
0.5
2.0
1.5
LOAD CURRENT (A)
1.0
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
2.5
3.0
8302 G01
T
A
= 25°C, unless otherwise noted.
Switching Frequency
vs Load Current
500
FRONT PAGE APPLICATION
Output Temperature Variation
5.3
5.2
5.1
R
TC
= 115k
5.0
4.9
4.8
4.7
–50 –25
R
TC
= OPEN
FRONT PAGE APPLICATION
V
IN
= 12V
I
OUT
= 1A
FREQUENCY (kHz)
400
300
200
100
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G02
0
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
0
0.5
2.0
1.0
1.5
LOAD CURRENT (A)
2.5
3.0
8302 G03
Boundary Mode Waveforms
V
SW
20V/DIV
Discontinuous Mode Waveforms
Burst Mode Waveforms
V
SW
20V/DIV
V
OUT
50mV/DIV
2µs/DIV
FRONT PAGE APPLICATION
V
IN
= 12V
I
OUT
= 2A
8302 G04
V
SW
20V/DIV
V
OUT
50mV/DIV
2µs/DIV
FRONT PAGE APPLICATION
V
IN
= 12V
I
OUT
= 0.5A
8302 G05
V
OUT
50mV/DIV
20µs/DIV
FRONT PAGE APPLICATION
V
IN
= 12V
I
OUT
= 10mA
8302 G06
V
IN
Shutdown Current
10
T
J
= 150°C
T
J
= 25°C
T
J
= –55°C
V
IN
Quiescent Current,
Sleep Mode
140
130
120
I
Q
(µA)
110
100
90
80
T
J
= 25°C
T
J
= –55°C
I
Q
(µA)
T
J
= 150°C
420
V
IN
Quiescent Current,
Active Mode
T
J
= 150°C
8
400
I
Q
(µA)
6
380
T
J
= 25°C
T
J
= –55°C
4
2
360
340
0
0
10
20
30
V
IN
(V)
40
50
8302 G07
0
10
20
30
V
IN
(V)
40
50
8302 G08
320
0
10
20
30
V
IN
(V)
40
50
8302 G09
4
8302fa
For more information
www.linear.com/LT8302
LT8302
Typical perForMance characTerisTics
EN/UVLO Enable Threshold
1.240
1.235
1.230
V
EN/UVLO
(V)
I
HYST
(µA)
1.225
1.220
1.215
1.210
1.205
1.200
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G10
T
A
= 25°C, unless otherwise noted.
INTV
CC
Voltage vs Temperature
3.10
3.05
3.00
V
INTVCC
(V)
2.95
2.90
2.85
2.80
–50 –25
I
INTVCC
= 0mA
I
INTVCC
= 10mA
EN/UVLO Hysteresis Current
5
RISING
4
3
FALLING
2
1
0
–50 –25
0
25 50
75 100 125 150
TEMPERATURE (°C)
8302 G11
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G12
INTV
CC
Voltage vs V
IN
3.10
3.05
3.00
V
INTVCC
(V)
2.95
2.90
2.85
2.80
I
INTVCC
= 0mA
I
INTVCC
= 10mA
2.8
2.7
INTV
CC
UVLO Threshold
40
30
20
V
INTVCC (V)
RISING
FALLING
VOLTAGE (mV)
2.6
2.5
2.4
2.3
2.2
–50 –25
10
0
–10
–20
–30
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G14
(R
FB
-V
IN
) Voltage
I
RFB
= 125µA
I
RFB
= 100µA
I
RFB
= 75µA
5
10
15
20
25 30
V
IN
(V)
35
40
45
–40
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G15
8302 G13
1.010
1.008
1.006
1.004
V
RREF
(V)
1.002
1.000
0.998
0.996
0.994
0.992
R
REF
Regulation Voltage
1.010
1.008
1.006
1.004
V
RREF
(V)
R
REF
Line Regulation
1.5
1.4
1.3
1.2
V
TC
(V)
1.1
1.0
0.9
0.8
0
10
20
30
V
IN
(V)
40
50
8302 G17
TC Pin Voltage
1.002
1.000
0.998
0.996
0.994
0.992
0.990
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G16
0.990
0.7
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
8302 G18
8302fa
For more information
www.linear.com/LT8302
5
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