NOT RECOMMENDED FOR NEW DESIGNS
Contact Linear Technology for Potential Replacement
LT3782
2-Phase Step-UP
DC/DC Controller
DESCRIPTION
The LT
®
3782 is a current mode two phase step-up DC/DC
converter controller. Its high switching frequency (up to
500kHz) and 2-phase operation reduce system filtering
capacitance and inductance requirements.
With 10V gate drive (V
CC
≥13V) and 4A peak drive current,
the LT3782 can drive most industrial grade high power
MOSFETs with high efficiency. For synchronous applica-
tions, the LT3782 provides synchronous gate signals with
programmable falling edge delay to avoid cross conduc-
tion when using external MOSFET drivers. Other features
include programmable undervoltage lockout, soft-start,
current limit, duty cycle clamp (50% or higher) and slope
compensation.
The LT3782 is available in thermally enhanced 28-lead
TSSOP and 4mm
×
5mm QFN packages.
For new designs use the LT3782A which has improved
phase matching
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6144194.
FEATURES
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2-Phase Operation Reduces Required Input and
Output Capacitance
Programmable Switching Frequency:
150kHz to 500kHz
6V to 40V Input Range
10V Gate Drive with V
CC
≥13V
High Current Gate Drive (4A)
Programmable Soft-Start and Current Limit
Programmable Slope Compensation for
High Noise Immunity
MOSFET Gate Signals with Programmable
Falling Edge Delay for External Synchronous
Drivers
Programmable Undervoltage Lockout
Programmable Duty Cycle Clamp (50% or Higher)
Thermally Enhanced 28-Lead TSSOP and 4mm
×
5mm
QFN Packages
APPLICATIONS
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Industrial Equipment
Telecom Infrastructure
Interleaved Isolated Power Supply
TYPICAL APPLICATION
50V 4A Boost Converter
V
IN
10V TO 36V
R6
825k
C
IN
10μF
50V
2x
R8
274k
1μF
RUN
L1
V
CC
GBIAS1
GBIAS2
GBIAS
BGATE1
R
S1
0.004Ω
V
EE1
SLOPE
DELAY
R
FREQ
80k
DCL
R
SET
SS
0.1μF
V
C
13k
100pF
6.8nF
GND
V
EE2
10Ω
SENSE1
+
SENSE1
–
SENSE2
+
SENSE2
–
FB
10nF
10nF
R
F1
475k
10Ω
85
0
1
2
3
I
OUT
(A)
4
5
3782 TA01b
D1
30BQ060
D2
30BQ060
+
C3
2μF
L2
M1
Si7852dp
2x
C
OUT1
10μF
50V
2x
V
OUT
50V, 4A
+
Efficiency and Power Loss
vs Load Current
97
EFFICIENCY
95
V
IN
= 12V
POWER LOSS (W)
EFFICIENCY (%)
93
91
89
87
V
IN
= 12V
V
IN
= 24V
POWER LOSS
3
0
12
9
6
V
IN
= 24V
15
18
C
OUT2
220μF
LT3782
R
SLOPE
59k
BGATE2
M2
Si7852dp
2x
R
S2
0.004Ω
L1, L2: PB2020.223
C
IN
, C
OUT1
: X7R, TDK
3782 TA01
R
F2
24.9k
3782fg
1
LT3782
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
CC
Supply Voltage ...................................................40V
GBIAS, GBIAS1, GBIAS2 Pin
(Externally Forced) ....................................................14V
SYNC, RUN Pin .........................................................30V
Operating Junction Temperature
Range (Notes 2, 3) ................................. –40°C to 125°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
SS ................................................................ –0.3V to 6V
SENSE1
+
, SENSE2
+
,
SENSE1
–
, SENSE2
–
..................................... –0.3V to 2V
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SGATE1
SGATE2
GBIAS
SGATE2
SGATE1
NC
GND
SYNC
DELAY
DCL
SENSE1
+
SENSE1
–
1
2
3
4
5
6
7
8
9
29
28 GBIAS
27 V
CC
26 NC
25 NC
24 V
EE1
23 BGATE1
22 GBIAS1
21 GBIAS2
20 BGATE2
19 V
EE2
18 NC
17 RUN
16 FB
15 V
C
28 27 26 25 24 23
SYNC 1
DELAY 2
DCL 3
SENSE1
+
4
SENSE1
–
29
5
SLOPE 6
R
SET
7
SENSE2
–
8
9 10 11 12 13 14
SLOPE 10
R
SET
11
SENSE2
–
12
SENSE2
+
13
SS 14
SENSE2
+
FE PACKAGE
28-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/ W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
UFD PACKAGE
28-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/ W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3782EFE#PBF
LT3782IFE#PBF
LT3782EUFD#PBF
LEAD BASED FINISH
LT3782EFE
LT3782IFE
LT3782EUFD
TAPE AND REEL
LT3782EFE#TRPBF
LT3782IFE#TRPBF
LT3782EUFD#TRPBF
TAPE AND REEL
LT3782EFE#TR
LT3782IFE#TR
LT3782EUFD#TR
PART MARKING
LT3782EFE
LT3782IFE
3782
PART MARKING
LT3782EFE
LT3782IFE
3782
PACKAGE DESCRIPTION
28-Lead Plastic TSSOP
28-Lead Plastic TSSOP
28-Lead (4mm
×
5mm) Plastic QFN
PACKAGE DESCRIPTION
28-Lead Plastic SSOP
28-Lead Plastic SSOP
28-Lead (4mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
RUN
NC
SS
V
C
FB
V
EE1
22 BGATE1
21 GBIAS1
20 NC
19 NC
18 GBIAS2
17 BGATE2
16 V
EE2
15 NC
GND
V
CC
3782fg
2
LT3782
The
●
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 13V, R
SET
= 80k, no load on any outputs, unless otherwise noted.
PARAMETER
Overall
Supply Voltage (V
CC
)
Supply Current (I
VCC
)
Shutdown
RUN Threshold
RUN Threshold Hysteresis
Supply Current in Shutdown
RUN Pin Input Current
Voltage Amplifier g
m
Reference Voltage (V
REF
)
Transconductance
Input Current I
FB
V
C
High
V
C
Low
Source Current I
VC
Sink Current I
VC
V
C
Threshold for Switching Off (BGATE1, BGATE2 Low)
Soft-Start Current I
SS
Current Amplifier CA1, CA2
Voltage Gain ΔV
C
/ΔV
SENSE
Current Limit (V
SENSE1+
– V
SENSE1–
) (V
SENSE2+
– V
SENSE2–
)
Input Current (I
SENSE1+
, I
SENSE1–
, I
SENSE2+
, I
SENSE2–
)
Oscillator
Switching Frequency
R
SET
= 130k
R
SET
= 80k
R
SET
= 40k
Rising Edge V
SYNC
R
SET
= 130k
R
SET
= 80k
R
SET
= 40k
R
SET
= 80k
V
FB
= V
REF
– 25mV, R
SET
> 80k
R
SET
= 40k
R
SET
= 80k, V
DCL
≤ 0.3V
V
DCL
= 1.2V
V
DCL
= V
RSET
V
DCL
≤ 0.3V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
6
TYP
MAX
40
UNITS
V
mA
V
mV
mA
μA
μA
V
V
μmho
μA
V
V
μA
μA
V
μA
V
C
≤ 0.5V (Switching Off), V
CC
≤ 40V
2.3
11
2.45
80
0.4
40
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2.6
0.65
90
–2
2.464
2.488
370
0.6
0.4
14
28
15
1V ≤ RUN ≤ V
REF
, V
CC
≤ 30V
RUN ≤ 0.3V, V
CC
≤ 30V
V
RUN
= 2.3V
–0.5
2.42
2.4
200
2.44
260
0.2
1.5
0.35
8
13
11
20
10
4
50
62
60
130
212
386
0.8
180
290
550
2.3
90
83
94
90
50
75
Max Duty Cycle
–0.1
154
250
465
1.2
V
VC
= 1V, ΔI
VC
= ±2μA
V
FB
= V
REF
I
VC
= 0
I
VC
= 0
V
VC
= 0.7V – 1V, V
FB
= V
REF
– 100mV
V
VC
= 0.7V – 1V, V
FB
= V
REF
+ 100mV
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0.3
6
V
SS
= 0.1V – 2.8V
80
mV
μA
ΔV
SENSE
= 0V
177
288
533
2
240
392
715
kHz
kHz
kHz
V
kHz
kHz
kHz
V
%
%
%
%
Synchronization Pulse Threshold on SYNC Pin
Synchronization Frequency Range
(Note: Operation Switching Frequency Equals
Half of the Synchronization Frequency)
V
RSET
Maximum Duty Cycle
Duty Cycle Limit
DCL Pin Input Current
–0.3
μA
3782fg
3
LT3782
The
●
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 13V, R
SET
= 80k, no load on any outputs, unless otherwise noted.
PARAMETER
Gate Driver
V
GBIAS
BGATE1, BGATE2 High Voltage
BGATE1, BGATE2 Source Current (Peak)
BGATE1, BGATE2 Low Voltage
BGATE1, BGATE2 Sink Current (Peak)
SGATE1, SGATE2 High Voltage
SGATE1, SGATE2 Low Voltage
SGATE1, SGATE2 Peak Current
Delay of BGATE High
I
GBIAS
< 70mA
13V ≤ V
CC
≤ 24V, I
BGATE
= –100mA
V
CC
= 8V, I
BGATE
= –100mA
Capacitive Load >22μF
Capacitive Load >50μF
8V ≤ V
CC
≤ 24V, I
BGATE
= 100mA
Capacitive Load >22μF
Capacitive Load >50μF
8V ≤ V
CC
≤ 24V, I
SGATE
= –20mA
8V ≤ V
CC
≤ 24V, I
SGATE
= 20mA
500pF Load
DELAY Pin and R
SET
Pin Shorted
V
DELAY
= 1V
V
DELAY
= 0.5V
V
DELAY
= 0.25V
V
DELAY
= 0.25V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
10.2
7.8
3.8
TYP
11
9.2
5
3
4
0.5
3
4
MAX
11.7
10.5
UNITS
V
V
V
A
A
0.7
V
A
A
4.5
5.5
0.5
100
100
150
250
500
–0.1
6.7
0.7
V
V
mA
ns
ns
ns
ns
Delay Pin Input Current
–0.3
μA
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 LT3782E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3782I is guaranteed to
meet performance specifications over the full –40°C to 125°C operating
junction temperature range.
Note 3:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
3782fg
4
LT3782
TYPICAL PERFORMANCE CHARACTERISTICS
V
GBIAS
vs I
GBIAS
11.0
10.9
10.8
10.7
V
GBIAS
(V)
T
A
= 25°C unless otherwise noted.
ΔV
REF
vs V
CC
, ΔFrequency vs V
CC
(R
SET
= 80k)
3
2
1
ΔV
REF
(mV)
I
CC
vs V
CC
20
18
16
14
12
10
8
ΔV
REF
6
4
ΔFrequency
2
0
–2
–4
6
9
12
15
18
V
CC
(V)
3782 G03
ΔFREQUENCY (kHz)
10.5
10.4
10.3
10.2
10.1
10.0
0
50
I
GBIAS
(mA)
3782 G01
I
CC
(mA)
10.6
12
10
8
6
4
2
0
–1
–2
–3
–4
–5
100
0
6
8 10 12 14 16 18 20 22 24 26 28 30
V
CC
(V)
3782 G02
21
24
27
30
Switching Frequency vs R
FREQ
600
Reference Voltage
vs Temperature
2.446
2.444
REFERENCE VOLTAGE (V)
V
GBIAS
vs I
GBIAS
at Start-Up
(Charging 2μF)
14
12
10
V
GBIAS
800
700
600
500
400
300
I
GBIAS
2
200
100
0
250μ
500μ
TIME (s)
750μ
0
1m
3782 G06
500
FREQUENCY (kHz)
2.442
V
GBIAS
(V)
400
8
6
4
I
GBIAS
(mA)
2.440
2.438
2.436
2.434
0
25
75
100
125
50
JUNCTION TEMPERATURE (°C)
150
3782 G05
300
200
0
–2
100
0
20 40 60 80 100 120 140 160 180 200
R
FREQ
(kΩ)
3782 G04
SGATE (Low) to BGATE (High)
Delay vs V
DELAY
(R
SET
= 80k)
1000
900
800
105
Switching Frequency
vs Duty Cycle
120
110
MAXIMUM DUTY CYCLE (%)
Maximum Duty Cycle Limit vs
V
DCL
(R
SET
= 80k)
100
100
90
80
70
60
50
DUTY CYCLE (%)
700
DELAY (ns)
600
500
400
300
200
100
0
0
0.5
1.5
1.0
V
DELAY
(V)
2.0
2.5
3782 G07
95
90
85
80
100
40
200
400
500
300
SWITCHING FREQUENCY (kHz)
600
3782 G08
0
0.3
0.6
0.9
1.5
V
DCL
(V)
1.2
1.8
2.1
2.4
3782 G09
3782fg
5
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