FEATURES
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LT8331
Low I
Q
Boost/SEPIC/
Flyback/Inverting Converter
with 0.5A, 140V Switch
DESCRIPTION
The
LT
®
8331
is a current mode DC/DC converter with a
140V, 0.5A switch operating from a 4.5V to 100V input.
With a unique single feedback pin architecture, it is ca-
pable of boost, SEPIC, flyback or inverting configurations.
Burst Mode operation consumes as low as 6μA quiescent
current to maintain high efficiency at very low output cur-
rents, while keeping typical output ripple below 20mV.
The internally-compensated current mode architecture
results in stable operation over a wide range of input and
output voltages and programmable switching frequencies
between 100kHz to 500kHz. A SYNC/MODE pin allows
synchronization to an external clock. It can also be used to
select between burst or pulse-skipping modes of operation.
For increased efficiency, a BIAS pin can accept a second
input to supply the INTV
CC
regulator. Additional features
include frequency foldback and programmable soft-start
for controlling inductor current during start-up.
The LT8331 is available in a thermally-enhanced MSOP
package with four pins removed for high voltage spacings.
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.
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Wide Input Voltage Range: 4.5V to 100V
Ultralow Quiescent Current and Low Ripple
Burst Mode
®
Operation: I
Q
= 6µA
0.5A, 140V Power Switch
Positive or Negative Output Voltage Programming
with a Single Feedback Pin
Programmable Frequency (100kHz to 500kHz)
Synchronizable to an External Clock
BIAS Pin for Higher Efficiency
Programmable Undervoltage Lockout (UVLO)
Thermally-Enhanced High Voltage MSOP Package
APPLICATIONS
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Industrial and Automotive
Telecom
Medical Diagnostic Equipment
Portable Electronics
TYPICAL APPLICATION
48V Output SEPIC Converter
220 H
V
IN
36V TO
72V
2.2µF
V
OUT
= 48V
150mA AT V
IN
= 36V
165mA AT V
IN
= 48V
190mA AT V
IN
= 72V
EFFICIENCY (%)
100
90
80
70
60
50
40
30
20
10
1µF
8331 TA01a
Efficiency and Power Loss
2.0
•
1µF
×2
1M
V
IN
LT8331
EN/UVLO
SYNC/MODE
GND
SW1-2
220 H
4.7µF
×4
EFFICIENCY
1.5
POWER LOSS (W)
•
FBX
BIAS
V
OUT
1M
POWER LOSS
1.0
59k
RT
63.4k
450kHz
SS
INTV
CC
0.1µF
34.8k
0
V
IN
= 36V
V
IN
= 48V
V
IN
= 72V
0
50
100
150
LOAD CURRENT (mA)
0.5
0
200
8331 TA01b
8331fa
For more information
www.linear.com/LT8331
1
LT8331
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
EN/UVLO 1
V
IN
3
INTV
CC
NC
BIAS
NC
5
6
7
8
17
PGND,
GND
16 SW1
14 SW2
12
11
10
9
SYNC/MODE
SS
RT
FBX
SW ..........................................................................140V
V
IN
, EN/UVLO..........................................................100V
BIAS ..........................................................................60V
EN/UVLO Pin Above V
IN
Pin, SYNC.............................6V
INTV
CC
(Note 2) ..........................................................4V
FBX ...........................................................................±4V
Operating Junction Temperature (Note 3)
LT8331E, LT8331I .............................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
MSE PACKAGE
VARIATION: MSE16 (12)
16-LEAD PLASTIC MSOP
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 17) IS PGND AND GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT8331EMSE#PBF
LT8331IMSE#PBF
TAPE AND REEL
LT8331EMSE#TRPBF
LT8331IMSE#TRPBF
http://www.linear.com/product/LT8331#orderinfo
PART MARKING*
8331
8331
PACKAGE DESCRIPTION
16-Lead Plastic MSOP with 4 Pins Removed
16-Lead Plastic MSOP with 4 Pins Removed
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC
®
Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, EN/UVLO = 12V unless otherwise noted.
PARAMETER
V
IN
Operating Voltage Range
V
IN
Quiescent Current at Shutdown
V
EN/UVLO
= 0.2V
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
l
TYP
1
2
2.0
3.6
5.5
8.5
780
840
17
24
700
800
17
24
MAX
100
2
5
5
9.5
15
25
1420
1720
40
55
1080
1170
40
55
UNITS
V
μA
μA
μA
μA
μA
μA
µA
µA
µA
µA
µA
µA
µA
µA
8331fa
4.5
V
EN/UVLO
= 1.5V
l
V
IN
Quiescent Current
Sleep Mode (Not Switching)
Active Mode (Not Switching)
R
T
= 100k
SYNC = 0V
l
SYNC = 0V, BIAS = 0V
l
SYNC = 0V, BIAS = 5V
l
SYNC = INTV
CC
, BIAS = 0V
l
SYNC = INTV
CC
, BIAS = 5V
l
2
For more information
www.linear.com/LT8331
LT8331
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, EN/UVLO = 12V unless otherwise noted.
PARAMETER
BIAS Threshold
V
IN
Falling Threshold to Supply INTV
CC
BIAS Falling Threshold to Supply INTV
CC
FBX Regulation
FBX Regulation Voltage
FBX Line Regulation
FBX Pin Current
Oscillator
Switching Frequency (f
OSC
)
Minimum On-Time
Minimum Off-Time
SYNC/Mode, Mode Thresholds
SYNC/Mode, Clock Thresholds
f
SYNC
/f
OSC
Allowed Ratio
SYNC Pin Current
Switch
Maximum Switch Current Limit Threshold
Switch Overcurrent Threshold
Switch R
DS(ON)
Switch Leakage Current
EN/UVLO Logic
EN/UVLO Pin Threshold (Rising)
EN/UVLO Pin Threshold (Falling)
EN/UVLO Pin Current
Soft-Start
Soft-Start Charge Current
Soft-Start Pull-Down Resistance
SS = 1V
Fault Condition, SS = 0.1V
2
250
characterization and correlation with statistical process controls. The
LT8331I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 4:
The IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime.
8331fa
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
l
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TYP
4.4
4
BIAS – 1.6V
V
IN
– 0.4V
MAX
4.65
4.275
UNITS
V
V
V
V
Rising, BIAS Can Supply INTV
CC
Falling, BIAS Cannot Supply INTV
CC
BIAS = 12V
V
IN
= 12V
FBX > 0V
FBX < 0V
FBX > 0V, 4.5V < V
IN
< 100V
FBX < 0V, 4.5V < V
IN
< 100V
FBX = 1.6V, –0.8V
R
T
= 301k
R
T
= 100k
R
T
= 56.2k
SYNC = 0V
SYNC = INTV
CC
Rising to Select Pulse Skipping Mode
Falling to Select Burst Mode Operation
Rising
Falling
R
T
= 100k
SYNC = 2V
4.10
3.725
l
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1.568
–0.820
1.6
–0.80
0.005
0.005
1.632
–0.780
0.015
0.015
10
V
V
%/V
%/V
nA
kHz
kHz
kHz
ns
ns
ns
V
V
V
V
kHz
nA
A
A
Ω
l
–10
92
279
465
100
300
500
165
160
146
l
l
l
107
321
535
290
290
230
2.4
l
l
0.6
0.6
0.95
–40
2.0
1.1
1
2.4
1.25
40
l
0.5
0.6
1.15
1.7
0.1
0.7
Discharges SS Pin
I
SW
= 0.25A
V
SW
= 140V
Start Switching
Stop Switching
V
EN/UVLO
= 1.6V
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1
1.90
1.644
40
µA
V
V
nA
µA
Ω
1.576
1.556
–40
1.74
1.6
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:
INTV
CC
cannot be externally driven. No external loading is allowed
on this pin.
Note 3:
The LT8331E 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,
For more information
www.linear.com/LT8331
3
LT8331
TYPICAL PERFORMANCE CHARACTERISTICS
FBX Positive Regulation Voltage
vs Temperature
1.630
1.620
FBX VOLTAGE (V)
FBX VOLTAGE (V)
1.610
1.600
1.590
1.580
1.570
–50 –25
V
IN
= 12V
–0.785
–0.790
EN/UVLO PIN VOLTAGE (V)
–0.795
–0.800
–0.805
–0.810
–0.815
–50 –25
FBX Negative Regulation Voltage
vs Temperature
V
IN
= 12V
1.84
1.81
1.78
1.75
1.72
1.69
1.66
1.63
1.60
1.57
EN/UVLO Pin Thresholds
vs Temperature
V
IN
= 12V
EN/UVLO RISING (TURN-ON)
EN/UVLO FALLING (TURN-OFF)
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G01
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G02
1.54
–50 –25
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G03
Switching Frequency
vs Temperature
525
520
SWITCHING FREQUENCY (kHz)
515
510
505
500
495
490
485
480
475
–50 –25
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G04
Switching Frequency vs V
IN
520
SWITCHING FREQUENCY (kHz)
515
510
505
500
495
490
485
480
475
0
10 20 30 40 50 60 70 80 90 100
V
IN
(V)
8331 G05
Normalized Switching Frequency
vs FBX Voltage
NORMALIZED SWITCHING FREQUENCY (%)
125
V
IN
= 12V
V
IN
= 12V
525
100
75
50
25
0
–0.8
–0.4
0.0
0.4
0.8
FBX VOLTAGE (V)
1.2
1.6
8331 G06
Switch Current Limit vs
Duty Cycle
0.70
V
IN
= 12V
200
190
SWITCH CURRENT LIMIT (A)
180
170
160
150
140
0.50
0
20
40
60
DUTY CYCLE (%)
80
100
8331 G07
Switch Minimum On-Time
vs Temperature
180
170
MINIMUM OFF–TIME (ns)
160
150
140
130
120
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G08
Switch Minimum Off-Time
vs Temperature
MINIMUM ON–TIME (ns)
0.65
0.60
SYNC = 0V
SYNC = INTV
CC
0.55
130
–50 –25
110
–50 –25
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G09
8331fa
4
For more information
www.linear.com/LT8331
LT8331
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
Pin Current (Sleep Mode, Not
Switching) vs Temperature
10.00
8.75
V
IN
PIN CURRENT ( A)
7.50
6.25
5.00
3.75
2.50
1.25
0
–50 –25
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G10
V
IN
Pin Current (Active Mode, Not
Switching) vs Temperature
1000
950
V
IN
PIN CURRENT ( A)
900
850
800
750
700
650
600
–50 –25
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G11
V
IN
Pin Current (Active Mode, Not
Switching) vs Temperature
30
25
V
IN
PIN CURRENT ( A)
20
15
10
5
0
–50 –25
V
IN
= 12V
V
SYNC/MODE
= 0V
V
BIAS
= 5V
V
IN
= 12V
V
SYNC/MODE
= 0V
V
BIAS
= 0V
V
IN
= 12V
V
SYNC/MODE
= 0V
V
BIAS
= 0V
0 25 50 75 100 125 150 175
JUNCTION TEMPERATURE (°C)
8331 G12
Switching Waveforms
(in CCM)
Switching Waveforms
(in DCM/Light Burst Mode)
Switching Waveforms
(in Deep Burst Mode)
I
L1
+I
L2
200mA/DIV
I
L1
+I
L2
200mA/DIV
I
L1
+I
L2
200mA/DIV
V
SW
50V/DIV
V
SW
50V/DIV
V
SW
50V/DIV
2µs/DIV
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V, I
LOAD
= 165mA
8331 G13
2µs/DIV
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V, I
LOAD
= 15mA
8331 G14
5µs/DIV
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V, I
LOAD
= 3mA
8331 G15
Burst Frequency vs Load Current
600
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V
450
V
OUT
Transient Response: Load
Current Transients from 82.5mA
to 165mA to 82.5mA
V
OUT
Transient Response: Load
Current Transients from 5mA to
165mA to 5mA
SWITCHING FREQUENCY (kHz)
I
LOAD
100mA/DIV
I
LOAD
100mA/DIV
300
V
OUT
500mV/DIV
V
OUT
1V/DIV
150
200µs/DIV
0
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V
8331 G17
500µs/DIV
FRONT PAGE APPLICATION
V
IN
= 48V, V
OUT
= 48V
8331 G18
0
20
40
60
80
LOAD CURRENT (mA)
100
8331 G16
8331fa
For more information
www.linear.com/LT8331
5
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