FEATURES
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LT3759
Wide Input Voltage Range
Boost/SEPIC/Inverting
Controller
DESCRIPTION
The
LT
®
3759
is a wide input range, current mode, DC/DC
controller which is capable of regulating either positive or
negative output voltages from a single feedback pin. It can
be configured as a boost, SEPIC or inverting converter.
The LT3759 drives a low side external N-channel power
MOSFET. An internal LDO regulator draws power from
V
IN
or DRIVE to provide up to a 4.75V supply for the gate
driver. The fixed frequency, current-mode architecture
results in stable operation over a wide range of supply
and output voltages. The operating frequency of LT3759
can be set over a 100kHz to 1MHz range with an external
resistor, or can be synchronized to an external clock using
the SYNC pin.
The LT3759 features soft-start and frequency foldback
functions to limit inductor current during start-up and
output short-circuit. A window comparator on the FBX pin
reports via the
PGOOD
pin, providing output voltage status
indication. The device is available in a 12-Lead exposed
pad MSOP package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT and No R
SENSE
are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents including 7825665.
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Wide V
IN
Range: 1.6V to 42V
Positive or Negative Output Voltage Programming
with a Single Feedback Pin
PGOOD
Output Voltage Status Report
Accurate 50mV SENSE Threshold Voltage
Programmable Soft-Start
Programmable Operating Frequency (100kHz to 1MHz)
with One External Resistor
Synchronizable to an External Clock
Low Shutdown Current < 1µA
INTV
CC
Regulator Supplied from V
IN
or DRIVE
Programmable Input Undervoltage Lockout with
Hysteresis
Datacom and Industrial Boost, SEPIC and Inverting
Converters
Distributed Power Supplies
Portable Electronic Equipment
Automotive
APPLICATIONS
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TYPICAL APPLICATION
2.5V to 36V Input, 12V Output SEPIC Converter
Excellent for Automotive 12V Post Regulator
V
IN
2.5V TO
36V
L1A
C
IN
4.7µF
×4
100k
4.7µF ×2
V
OUT
12V
0.5A, 2.5V ≤ V
IN
≤ 8V
2A, 8V < V
IN
≤ 36V
L1B
C
OUT1
10µF
100
95
EFFICIENCY (%)
Efficiency vs Output Current
V
IN
= 12V
105k
EN/UVLO
118k
V
IN
GATE
SENSE
5m
DRIVE
SYNC
RT
105K
FBX
GND INTV
CC
7.5k
22nF
4.7µF
15.8K
M1
LT3759
PGOOD
90
85
80
TIE TO GND
IF NOT USED
41.2k
200kHz
0.1µF
SS
VC
+
C
OUT2
47µF
×4
75
0
0.5
2
1.5
1
OUTPUT CURRENT (A)
2.5
3759 TA01b
3759 TA01a
3759fc
For more information
www.linear.com/3759
1
LT3759
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
............................................................................42V
EN/UVLO (Note 2) .....................................................42V
DRIVE .......................................................................42V
PGOOD
......................................................................42V
INTV
CC
........................................................................8V
GATE .................................................................. (Note 3)
SYNC ..........................................................................8V
VC, SS .........................................................................3V
RT ............................................................................1.5V
SENSE ....................................................................±0.3V
FBX ................................................................. –3V to 3V
Operating Junction Temperature Range (Note 4)
LT3759E/LT3759I .............................. –40°C to 125°C
LT3759H ............................................ –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
VC
FBX
SS
RT
SYNC
PGOOD
1
2
3
4
5
6
12
11
10
9
8
7
EN/UVLO
V
IN
DRIVE
INTV
CC
GATE
SENSE
13
GND
MSE PACKAGE
12-LEAD PLASTIC MSOP
θ
JA
= 35°C/W TO 40°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3759EMSE#PBF
LT3759IMSE#PBF
LT3759HMSE#PBF
TAPE AND REEL
LT3759EMSE#TRPBF
LT3759IMSE#TRPBF
LT3759HMSE#TRPBF
PART MARKING*
3759
3759
3759
PACKAGE DESCRIPTION
12-Lead Plastic MSOP
12-Lead Plastic MSOP
12-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping
container. Consult LTC Marketing for information on non-standard 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/
3759fc
2
For more information
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LT3759
ELECTRICAL CHARACTERISTICS
PARAMETER
V
IN
Operating Voltage
V
IN
Shutdown I
Q
V
IN
Operating I
Q
DRIVE Shutdown Quiescent Current
DRIVE Quiescent Current (Not Switching)
SENSE Current Limit Threshold
SENSE Input Bias Current
Error Amplifier
FBX Regulation Voltage (V
FBX(REG)
)
FBX Pin Input Current
Transconductance g
m
(ΔI
2
/ΔV
FBX
)
VC Output Impedance
FBX Line Regulation [ΔV
FBX(REG)
/(ΔV
IN
• V
FBX(REG)
)]
VC Current Mode Gain (ΔV
VC
/ΔV
SENSE
)
VC Source Current
VC Sink Current
Oscillator
Switching Frequency
R
T
= 27.4k to GND, V
FBX
= 1.6V
R
T
= 86.6k to GND, V
FBX
= 1.6V
R
T
= 6.81k to GND, V
FBX
= 1.6V
FBX = 1.6V, –0.8V
270
300
100
1000
1.2
170
170
l
l
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, INTV
CC
= 4.75V, unless otherwise noted.
CONDITIONS
l
MIN
1.6
TYP
0.1
350
MAX
42
1
6
450
1
2
2.5
54
UNITS
V
µA
µA
µA
µA
µA
mA
mV
µA
EN/UVLO < 0.4V
EN/UVLO = 1.15V
EN/UVLO < 0.4V
EN/UVLO = 1.15V
R
T
= 27.4kΩ, DRIVE = 6V
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0.1
0.1
2.0
46
50
–55
l
l
Current Out of Pin
FBX > 0V
FBX < 0V
FBX = 1.6V
FBX = –0.8V
FBX = V
FBX(REG)
1.6V < V
IN
< 42V, FBX >0
1.6V < V
IN
< 42V, FBX <0
FBX = 0V, VC = 1.3V
FBX = 1.7V, VC = 1.3V
FBX = –0.85V, VC = 1.3V
1.580
–0.815
–10
1.6
–0.80
60
240
5
0.02
0.02
5
–13
13
10
1.620
–0.785
120
10
V
V
nA
nA
µs
MΩ
0.05
0.05
%/V
%/V
V/V
µA
µA
µA
330
kHz
kHz
kHz
V
ns
ns
V
V
µA
V
V
mA
mA
%
%
R
T
Voltage
GATE Minimum Off-Time
GATE Minimum On-Time
SYNC Input Low
SYNC Input High
SS Pull-Up Current
Low Dropout Regulators (DRIVE LDO and V
IN
LDO)
DRIVE LDO Regulation Voltage
V
IN
LDO Regulation Voltage
DRIVE LDO Current Limit
V
IN
LDO Current Limit
DRIVE LDO Load Regulation (ΔV
INTVCC
/V
INTVCC
)
V
IN
LDO Load Regulation (ΔV
INTVCC
/V
INTVCC
)
DRIVE LDO Line Regulation [ΔV
INTVCC
/(V
INTVCC
• ΔV
IN
)]
V
IN
LDO Line Regulation [ΔV
INTVCC
/(V
INTVCC
• ΔV
IN
)]
DRIVE LDO Dropout Voltage (V
DRIVE
– V
INTVcc
)
200
200
0.4
1.5
–14
4.6
3.6
–10.5
4.75
3.75
60
60
–1
–1
–0.6
–0.6
0.03
0.03
0.07
0.07
400
–7
4.9
3.9
SS = 0V, Current Out of Pin
DRIVE = 6V
DRIVE = 0V
INTV
CC
= 4V
DRIVE = 0V, INTV
CC
= 3V
0 < I
INTVCC
< 20mA, DRIVE = 6V
DRIVE = 0V, 0 < I
INTVCC
< 20mA
1.6V < V
IN
< 42V, DRIVE = 6V
DRIVE = 0V, 5V < V
IN
< 42V
DRIVE = 4V, I
INTVCC
= 20mA
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%/V
%/V
mV
3759fc
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190
For more information
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3
LT3759
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, INTV
CC
= 4.75V, unless otherwise noted.
PARAMETER
V
IN
LDO Dropout Voltage (V
IN
– V
INTVcc
)
INTV
CC
Undervoltage Lockout Threshold Falling
INTV
CC
Current in Shutdown
Logic
EN/UVLO Threshold Voltage Falling
EN/UVLO Rising Hysteresis
EN/UVLO Input Low Voltage
EN/UVLO Pin Bias Current Low
EN/UVLO Pin Bias Current High
FBX Power Good Threshold Voltage
FBX Overvoltage Threshold
PGOOD
Output Low (V
OL
)
PGOOD
Leakage Current
INTV
CC
Minimum Voltage to Enable
PGOOD
Function
INTV
CC
Minimum Voltage to Enable SYNC Function
NMOS Gate Drivers
GATE Output Rise Time (T
R
)
GATE Output Fall Time (T
F
)
GATE Output Low (V
OL
)
GATE Output High (V
OH
)
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:
For V
IN
below 4V, the EN/UVLO pin must not exceed V
IN
for proper
operation.
Note 3:
This pin is for switching purposes. Do not tie directly to a supply.
Note 4:
The LT3759E is guaranteed to meet performance specifications
from the 0°C to 125°C operating junction temperature range.
Specifications over the –40°C to 125°C operating junction temperature
INTV
CC
– 0.05
range are assured by design, characterization and correlation with
statistical process controls. The LT3759I is guaranteed over the full
–40°C to 125°C operating junction temperature range. The LT3759H is
guaranteed over the full –40°C to 150°C operating junction temperature
range. High junction temperatures degrade operating lifetimes. Operating
lifetime is derated at junction temperatures greater than 125°C.
Note 5:
The LT3759 is tested in a feedback loop which servos V
FBX
to the
reference voltages (1.6V and –0.8V) with the VC pin forced to 1.3V.
Note 6:
Rise and fall times are measured at 10% and 90% levels.
C
L
= 3300pF
C
L
= 3300pF
20
20
0.05
ns
ns
V
V
I
VIN
< 1μA
EN/UVLO = 1.15V
EN/UVLO = 1.30V
FBX > 0V,
PGOOD
Falling
FBX < 0V,
PGOOD
Falling
FBX > 0V,
PGOOD
Rising
FBX < 0V,
PGOOD
Rising
I
PGOOD
= 250µA
PGOOD
= 42V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
V
IN
= 3V, DRIVE = 0V,
I
INTVCC
= 20mA
EN/UVLO = 0V
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MIN
TYP
190
1.3
22
MAX
400
1.45
UNITS
mV
V
µA
1.17
1.22
20
1.27
0.4
V
mV
V
µA
nA
V
V
V
V
1.8
2.2
10
V
FBX(REG)
– 0.08
V
FBX(REG)
+ 0.04
V
FBX(REG)
+ 0.12
V
FBX(REG)
– 0.06
210
2.6
100
300
1
3.0
3.0
mV
µA
V
V
2.4
2.4
2.7
2.7
3759fc
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LT3759
TYPICAL PERFORMANCE CHARACTERISTICS
FBX Positive Regulation Voltage
vs Temperature
1.62
FBX REGULATION VOLTAGE (V)
FBX REGULATION VOLTAGE (V)
–0.78
T
A
= 25°C, unless otherwise noted.
Quiescent Current
vs Temperature
2.2
2.0
1.8
I
Q
(DRIVE)
FBX Negative Regulation Voltage
vs Temperature
1.61
–0.79
1.6
1.4
I
Q
(mA)
1.2
1.0
0.8
0.6
0.4
0.2
I
Q
(V
IN
)
V
IN
= 12V
DRIVE = 6V
1.60
–0.80
1.59
–0.81
1.58
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3759 G01
–0.82
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3759 G02
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3759 G03
Dynamic Quiescent Current
vs Switching Frequency
25
20
C
L
= 3300pF, DRIVE = 6V
100
90
80
70
I
Q
(mA)
15
R
T
(k)
I
Q
(DRIVE)
10
5
I
Q
(V
IN
)
0
800
600
200
400
SWITCHING FREQUENCY (kHz)
1000
3759 G04
R
T
vs Switching Frequency
Normalized Switching Frequency
vs FBX Voltage
120
NORMALIZED FREQUENCY (%)
100
80
60
40
20
0
–0.8
60
50
40
30
20
10
0
0 100 200 300 400 500 600 700 800 900 1000
SWITCHING FREQUENCY (kHz)
3759 G05
0
–0.4
0
0.4
0.8
1.2
1.6
3759 G06
FBX VOLTAGE (V)
Switching Frequency
vs Temperature
350
R
T
= 27.4k
53
52
SENSE THRESHOLD (mV)
51
50
49
48
250
–75 –50 –25
SENSE Current Limit Threshold
vs Temperature
53
52
SENSE THRESHOLD (mV)
0 25 50 75 100 125 150
TEMPERATURE (°C)
3759 G08
SENSE Current Limit Threshold
vs Duty Cycle
SWITCHING FREQUENCY (kHz)
325
51
50
49
48
47
300
275
0 25 50 75 100 125 150
TEMPERATURE (°C)
3759 G07
47
–75 –50 –25
0
20
40
60
80
100
3759 G09
DUTY CYCLE (%)
3759fc
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