POWER LOSS (mW)
LTC3788-1
2-Phase, Dual Output
Synchronous Boost Controller
FEATURES DESCRIPTION
n
Synchronous Operation for Highest Efficiency and The LTC 3788-1 is a high performance 2-phase dual
Reduced Heat Dissipation synchronous boost converter controller that drives all
n
Wide Input Range: 4.5V to 38V (40V Abs Max) and N-channel power MOSFETs. Synchronous rectification
Operates Down to 2.5V After Start-Up increases efficiency, reduces power losses and eases
n
Output Voltages Up to 60V thermal requirements, allowing the LTC3788-1 to be used
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1% 1.2V Reference Voltage in high power boost applications.
n
R or Inductor DCR Current Sensing
SENSE
A constant-frequency current mode architecture allows
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100% Duty Cycle Capability for Synchronous MOSFET
a phase-lockable frequency of up to 850kHz. OPTI-LOOP
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Low Quiescent Current: 125A
compensation allows the transient response to be opti-
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Phase-Lockable Frequency (75kHz to 850kHz)
mized over a wide range of output capacitance and ESR
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Programmable Fixed Frequency (50kHz to 900kHz)
values. The LTC3788-1 features a precision 1.2V refer-
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Adjustable Output Voltage Soft-Start
ence and a power good output indicator. A 4.5V to 38V
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Power Good Output Voltage Monitor
input supply range encompasses a wide range of system
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Low Shutdown Current I : <8A
Q
architectures and battery chemistries.
n
Internal LDO Powers Gate Drive from VBIAS or EXTV
CC
n Independent SS pins for each controller ramp the output
Available in a Narrow SSOP Package
voltages during start-up. The PLLIN/MODE pin selects
among Burst Mode operation, pulse-skipping mode or
APPLICATIONS
continuous inductor current mode at light loads.
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Industrial
For a leadless 32-pin QFN package with additional features
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Automotive
of adjustable current limit, clock out, phase modulation
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Medical
and two PGOOD outputs, see the LTC3788 data sheet.
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Military
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. patents, including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
TYPICAL APPLICATION
V 4.5V TO 12V START-UP VOLTAGE
IN
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
V
IN
Efficiency and Power Loss
4.7F vs Load Current
4.7F 220F
3m 4m
100 10000
TG1 VBIAS INTV TG2
CC
90
3.3H
1.25H BOOST1
BOOST2
V V
OUT OUT
80 1000
0.1F 0.1F
12V AT 5A 24V AT 3A
SW1 SW2
70
LTC3788-1
BG1 BG2
60 100
+ 50
+
SENSE1 SENSE2
40 10
SENSE1 SENSE2
30
PGND
V = 12V
IN
20 1
110k 232k V = 24V
OUT
VFB2 10 Burst Mode OPERATION
VFB1
FIGURE 9 CIRCUIT
FREQ 0 0.1
0.00001 0.0001 0.001 0.01 0.1 1 10
PLLIN/MODE
OUTPUT CURRENT (A)
ITH1 SS1 SGND SS2 ITH2
37881 TA01b
220F 15nF 15nF 220F
100pF
220pF
12.1k 2.7k 8.66k 12.1k
0.1F 0.1F
37881 TA01a
Rev D
1
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EFFICIENCY (%)LTC3788-1
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Notes 1, 3)
TOP VIEW
VBIAS ........................................................ 0.3V to 40V
1 SS1
ITH1 28
BOOST1, BOOST2 ...................................... 0.3V to 76V
2 PGOOD1
VFB1 27
SW1, SW2 .................................................. 0.3V to 70V
+
3 SW1
SENSE1 26
RUN1, RUN2 ................................................ 0.3V to 8V
4 TG1
SENSE1 25
Maximum Current Sourced into Pin
5 BOOST1
FREQ 24
from Source > 8V .............................................100A
6 BG1
PLLIN/MODE 23
PGOOD1, PLLIN/MODE ............................... 0.3V to 6V
7 VBIAS
SGND 22
INTV , (BOOST1-SW1, BOOST2-SW2) ...... 0.3V to 6V
CC
8 PGND
RUN1 21
EXTV ........................................................ 0.3V to 6V
CC 9 EXTV
RUN2 20
CC
+
SENSE1 , SENSE1 ,
10 INTV
SENSE2 19
CC
+
+
SENSE2 , SENSE2 .................................... 0.3V to 40V 11 BG2
SENSE2 18
+
12 BOOST2
SENSE1 SENSE1 , VFB2 17
+
13 TG2
ITH2 16
SENSE2 SENSE2 ................................. 0.3V to 0.3V
14 SW2
SS2 15
SS1, SS2, ITH1, ITH2, FREQ,
VFB1, VFB2 ...........................................0.3V to INTV
CC GN PACKAGE
28-LEAD PLASTIC SSOP
Operating Junction Temperature Range ....40C to 125C
T = 125C, = 80C/W
JMAX JA
Storage Temperature Range .................. 65C to 125C
Lead Temperature (Soldering, 10 seconds) ...........300C
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3788EGN-1#PBF LTC3788EGN-1#TRPBF LTC3788GN-1 28-Lead Plastic SSOP 40C to 125C
LTC3788IGN-1#PBF LTC3788IGN-1#TRPBF LTC3788GN-1 28-Lead Plastic SSOP 40C to 125C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T = 25C, VBIAS = 12V, unless otherwise noted (Note 2).
A
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
VBIAS Chip Bias Voltage Operating Range 4.5 38 V
VFB1,2 Regulated Feedback Voltage I = 1.2V (Note 4) l 1.188 1.200 1.212 V
TH
IFB1,2 Feedback Current (Note 4) 5 50 nA
V Reference Line Voltage Regulation V = 6V to 38V 0.002 0.02 %/V
REFLNREG IN
Rev D
2
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