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, enabling high power boost applications.
A 4.5V to 38V 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 LTC3787 can operate from
an input supply as low as 2.5V after start-up. The operat-
ing frequency can be set for a 50kHz to 900kHz range or
synchronized to an external clock using the internal PLL.
PolyPhase operation allows the LTC3787 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.
2-Phase 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 38V (40V Abs Max) and
Operates Down to 2.5V 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: 135μA
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Power Good Output Voltage Monitor
Low Shutdown Current, I
Q
< 8μA
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
n
n
n
n
Industrial
Automotive
Medical
Military
TYPICAL APPLICATION
12V to 24V/10A 2-Phase Synchronous Boost Converter
V
IN
4.5V TO 24V START-UP VOLTAGE
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
V
IN
Efficiency and Power Loss
vs Output Current
100
90
10000
4mΩ
4.7μF
TG1 VBIAS INTV
CC
4.7μF
TG2
4mΩ
47μF
80
EFFICIENCY (%)
70
60
50
40
30
1000
POWER LOSS (mW)
100
3.3μH
0.1μF
BOOST1
SW1
BOOST2
SW2
3.3μH
0.1μF
V
OUT
24V AT 10A
10
232k
LTC3787
BG1
BG2
SENSE1
+
SENSE1
–
SENSE2
+
VFB
SENSE2
–
FREQ
PGND
PLLIN/MODE
ITH SS SGND
12.1k
15nF
8.66k
100pF
0.1μF
3787 TA01a
V
IN
= 12V
1
V
OUT
= 24V
10
Burst Mode OPERATION
FIGURE 10 CIRCUIT
0
0.1
0.1
1
10
0.00001 0.0001 0.001 0.01
OUTPUT CURRENT (A)
20
220μF
3787 TA01b
BURST EFFICIENCY
BURST LOSS
3787fc
1
LTC3787
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 3)
VBIAS ........................................................ –0.3V to 40V
BOOST1 and BOOST2 ................................ –0.3V to 76V
SW1 and SW2............................................ –0.3V to 70V
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 6V
SENSE1
+
, SENSE1
–
, SENSE2
+
, SENSE2
–
... –0.3V to 40V
(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
PIN CONFIGURATION
TOP VIEW
SENSE1
–
ILIM
SENSE1
+
SENSE1
–
FREQ
PHASMD
CLKOUT
PLLIN/MODE
SGND
RUN
1
2
3
4
5
6
7
8
9
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 NC
FREQ 1
PHASMD 2
CLKOUT 3
PLLIN/MODE 4
SGND 5
RUN 6
SS 7
SENSE2
–
8
9 10 11 12 13 14
SENSE2
+
VFB
ITH
NC
SW2
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
–
11
SENSE2
+
12
VFB 13
ITH 14
GN PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 90°C/W
UFD PACKAGE
28-LEAD (4mm 5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE CONNECTED TO GND
ORDER INFORMATION
LEAD FREE FINISH
LTC3787EUFD#PBF
LTC3787IUFD#PBF
LTC3787HUFD#PBF
LTC3787MPUFD#PBF
LTC3787EGN#PBF
LTC3787IGN#PBF
LTC3787HGN#PBF
LTC3787MPGN#PBF
TAPE AND REEL
LTC3787EUFD#TRPBF
LTC3787IUFD#TRPBF
LTC3787HUFD#TRPBF
LTC3787MPUFD#TRPBF
LTC3787EGN#TRPBF
LTC3787IGN#TRPBF
LTC3787HGN#TRPBF
LTC3787MPGN#TRPBF
PART MARKING*
3787
3787
3787
3787
LTC3787GN
LTC3787GN
LTC3787GN
LTC3787GN
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/
3787fc
2
LTC3787
ELECTRICAL CHARACTERISTICS
SYMBOL
VBIAS
V
FB
I
FB
V
REFLNREG
V
LOADREG
PARAMETER
Chip Bias Voltage Operating Range
Regulated Feedback Voltage
Feedback Current
Reference Line Voltage Regulation
Output Voltage Load Regulation
(Note 4)
I
TH
= 1.2V (Note 4)
(Note 4)
VBIAS = 6V to 38V
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 2V
g
m
I
Q
Error Amplifier Transconductance
Input DC Supply Current
Pulse-Skipping or Forced Continuous Mode
Sleep Mode
Shutdown
INTV
CC
Undervoltage Lockout Thresholds
RUN Pin ON Threshold
RUN Pin Hysteresis
RUN Pin Hysteresis Current
RUN Pin Current
Soft-Start Charge Current
Maximum Current Sense Threshold
V
RUN
> 1.28V
V
RUN
< 1.28V
V
SS
= GND
V
FB
= 1.1V, I
LIM
= INTV
CC
V
FB
= 1.1V, I
LIM
= Float
V
FB
= 1.1V, I
LIM
= GND
V
FB
= 1.1V, I
LIM
= INTV
CC
V
FB
= 1.1V, I
LIM
= Float
V
FB
= 1.1V, I
LIM
= GND
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
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