output synchronous boost converter controller that drives
two N-channel power MOSFET stages out-of-phase.
Multiphase operation reduces input and output capacitor
requirements and allows the use of smaller inductors than
the single-phase equivalent. Synchronous rectification in-
creases efficiency, reduces power losses and eases thermal
requirements, simplifying high power boost applications.
A 4.5V to 60V input supply range encompasses a wide
range of system architectures and battery chemistries.
When biased from the output of the boost converter or
another auxiliary supply, the LTC3784 can operate from an
input supply as low as 2.3V after start-up. The operating
frequency can be set within a 50kHz to 900kHz range or
synchronized to an external clock using the internal PLL.
PolyPhase operation allows the LTC3784 to be configured
for 2-, 3-, 4-, 6- and 12-phase operation.
The SS pin ramps the output voltage during start-up. The
PLLIN/MODE pin selects Burst Mode
®
operation, pulse-
skipping mode or forced continuous mode at light loads.
L,
LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase
are registered trademarks and No R
SENSE
and ThinSOT are trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by
U. S. Patents, including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
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PolyPhase
®
Operation Reduces Required Input and
Output Capacitance and Power Supply Induced Noise
Synchronous Operation for Highest Efficiency and
Reduced Heat Dissipation
Wide V
IN
Range: 4.5V to 60V (65V Abs Max);
Operates Down to 2.3V After Start-Up
Output Voltage Up to 60V
±1% 1.200V Reference Voltage
R
SENSE
or Inductor DCR Current Sensing
100% Duty Cycle Capability for Synchronous MOSFET
Low Quiescent Current: 28μA
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Power Good Output Voltage Monitor
Low Shutdown Current, I
Q
< 4µA
Internal LDO Powers Gate Drive from VBIAS or EXTV
CC
Thermally Enhanced Low Profile 28-Pin 4mm × 5mm
QFN Package and Narrow SSOP Package
applicaTions
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Industrial
Automotive
Medical
Military
Typical applicaTion
240W, 12V to 24V/10A 2-Phase Synchronous Boost Converter
4m
47µF
SENSE1
+
SENSE1
–
BG1
BOOST1
VBIAS
SW1
LTC3784
TG1
INTV
CC
0.1µF
V
OUT
24V AT 10A
220µF
3.3µH
Efficiency and Power Loss
vs Output Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
BURST EFFICIENCY
BURST LOSS
V
IN
= 12V
V
OUT
= 24V
Burst Mode OPERATION
FIGURE 10 CIRCUIT
1
10
3784 TA01b
V
IN
4.5V TO 60V
DOWN TO 2.3V AFTER
STARTUP IF VBIAS IS
POWERED FROM V
OUT
10000
1000
POWER LOSS (mW)
4.7µF
4m
3.3µH
SENSE2
+
SENSE2
–
BG2
BOOST2
FREQ
SW2
OVMODE
TG2
PLLIN/MODE
ITH
VFB
SS
SGND PGND
100pF
0.1µF
0.1µF
V
OUT
FOLLOWS V
IN
FOR V
IN
> 24V
100
10
1
15nF
8.66k
232k
12.1k
3784 TA01a
0
0.1
0.00001 0.0001 0.001 0.01
OUTPUT CURRENT (A)
0.1
3784fb
For more information
www.linear.com/LTC3784
1
LTC3784
absoluTe MaxiMuM raTings
(Notes 1, 3)
VBIAS ........................................................ –0.3V to 65V
BOOST1 and BOOST2 .................................–0.3V to 71V
SW1 and SW2............................................... –5V to 65V
RUN ............................................................. –0.3V to 8V
Maximum Current Sourced into Pin
From Source >8V ..............................................100µA
PGOOD, PLLIN/MODE ................................. –0.3V to 6V
INTV
CC
, (BOOST1 - SW1), (BOOST2 - SW2) ...–0.3V to 6V
EXTV
CC
...................................................... –0.3V to 14V
SENSE1
+
, SENSE1
–
, SENSE2
+
, SENSE2
–
... –0.3V to 65V
(SENSE1
+
- SENSE1
–
), (SENSE2
+
- SENSE2
–
) ...–0.3V to 0.3V
ILIM, SS, ITH, FREQ, PHASMD, VFB ..... –0.3V to INTV
CC
Operating Junction Temperature
Range (Note 2)........................................–55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) SSOP ........ 300°C
pin conFiguraTion
TOP VIEW
SENSE1
–
ILIM
SENSE1
+
SENSE1
–
FREQ
PHASMD
CLKOUT
PLLIN/MODE
SGND
RUN
SENSE2
–
1
2
3
4
5
6
7
8
9
11
28 PGOOD
27 SW1
26 TG1
25 BOOST1
24 BG1
23 VBIAS
22 PGND
21 EXTV
CC
20 INTV
CC
19 BG2
18 BOOST2
17 TG2
16 SW2
15 OVMODE
FREQ 1
PHASMD 2
CLKOUT 3
PLLIN/MODE 4
SGND 5
RUN 6
SS 7
SENSE2
–
8
9 10 11 12 13 14
VFB
ITH
OVMODE
SW2
SENSE2
+
TG2
29
GND
TOP VIEW
SENSE1
+
PGOOD
SW1
ILIM
TG1
22 BOOST1
21 BG1
20 VBIAS
19 PGND
18 EXTV
CC
17 INTV
CC
16 BG2
15 BOOST2
28 27 26 25 24 23
SS 10
SENSE2
+
12
VFB 13
ITH 14
GN PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 80°C/W
UFD PACKAGE
28-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE CONNECTED TO GND
orDer inForMaTion
LEAD FREE FINISH
LTC3784EUFD#PBF
LTC3784IUFD#PBF
LTC3784HUFD#PBF
LTC3784MPUFD#PBF
LTC3784EGN#PBF
LTC3784IGN#PBF
LTC3784HGN#PBF
LTC3784MPGN#PBF
TAPE AND REEL
LTC3784EUFD#TRPBF
LTC3784IUFD#TRPBF
LTC3784HUFD#TRPBF
LTC3784MPUFD#TRPBF
LTC3784EGN#TRPBF
LTC3784IGN#TRPBF
LTC3784HGN#TRPBF
LTC3784MPGN#TRPBF
PART MARKING*
3784
3784
3784
3784
LTC3784GN
LTC3784GN
LTC3784GN
LTC3784GN
PACKAGE DESCRIPTION
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead (4mm
×
5mm) Plastic QFN
28-Lead Plastic SSOP
28-Lead Plastic SSOP
28-Lead Plastic SSOP
28-Lead Plastic SSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
–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. *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/
3784fb
2
For more information
www.linear.com/LTC3784
LTC3784
elecTrical characTerisTics
SYMBOL
PARAMETER
Main Control Loop
VBIAS
Chip Bias Voltage Operating Range
SENSE Pins Common Mode Range (BOOST
Converter Input Supply Voltage V
IN
)
Regulated Feedback Voltage
V
FB
Feedback Current
Reference Line Voltage Regulation
Output Voltage Load Regulation
(Note 4)
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
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