LTC3788-1
2-Phase, Dual Output
Synchronous Boost Controller
FEATURES
DESCRIPTION
The LTC®3788-1 is a high performance 2-phase dual
synchronous boost converter controller that drives all
N-channel power MOSFETs. Synchronous rectification
increases efficiency, reduces power losses and eases
thermal requirements, allowing the LTC3788-1 to be used
in high power boost applications.
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Synchronous Operation for Highest Efficiency and
Reduced Heat Dissipation
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Wide Input Range: 4.5V to 38V (40V Abs Max) and
Operates Down to 2.5V After Start-Up
Output Voltages Up to 60V
±±1 ±.2V Reference Voltage
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R
or Inductor DCR Current Sensing
SENSE
A constant-frequency current mode architecture allows
a phase-lockable frequency of up to 850kHz. OPTI-LOOP
compensationallowsthetransientresponsetobeoptimized
over a wide range of output capacitance and ESR values.
The LTC3788-1 features a precision 1.2V reference and a
power good output indicator. A 4.5V to 38V input supply
range encompasses a wide range of system architectures
and battery chemistries.
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±001 Duty Cycle Capability for Synchronous MOSFET
Low Quiescent Current: 125μA
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Adjustable Output Voltage Soft-Start
Power Good Output Voltage Monitor
Low Shutdown Current I : <8ꢀA
Internal LDO Powers Gate Drive from VBIAS or EXTV
Available in a Narrow SSOP Package
Q
CC
Independent SS pins for each controller ramp the output
voltages during start-up. The PLLIN/MODE pin selects
among Burst Mode operation, pulse-skipping mode or
continuous inductor current mode at light loads.
APPLICATIONS
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Industrial
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Automotive
Foraleadless32-pinQFNpackagewithadditionalfeatures
of adjustable current limit, clock out, phase modulation
and two PGOOD outputs, see the LTC3788 data sheet.
L, LT, LTC, LTM, Linear Technology, OPTI-LOOP, Burst Mode and the Linear logo are registered
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Medical
Military
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trademarks and No R
and ThinSOT are trademarks of Linear Technology Corporation.
SENSE
All other trademarks are the property of their respective owners. Protected by U. S. Patents,
including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
V
4.5V TO 12V START-UP VOLTAGE
IN
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
TYPICAL APPLICATION
V
IN
Efficiency and Power Loss
vs Load Current
4.7μF
TG2
4.7μF
220μF
3mΩ
4mΩ
100
90
10000
1000
100
10
TG1 VBIAS INTV
BOOST1
CC
3.3μH
1.25μH
BOOST2
SW2
V
V
OUT
12V AT 5A
OUT
24V AT 3A
0.1μF
80
0.1μF
SW1
70
LTC3788-1
BG1
BG2
60
50
+
+
SENSE1
SENSE2
–
40
30
20
10
0
–
SENSE1
SENSE2
RUN1
PGND
V
V
= 12V
110k
IN
OUT
1
RUN2
VFB2
EXTV
CC
= 24V
VFB1
232k
Burst Mode OPERATION
FIGURE 9 CIRCUIT
PGOOD1
FREQ
PLLIN/MODE
0.1
0.00001 0.0001 0.001 0.01
0.1
1
10
OUTPUT CURRENT (A)
ITH1 SS1 SGND SS2 ITH2
37881 TA01b
15nF
220μF
220μF
15nF
2.7k
100pF
220pF
12.1k
8.66k
12.1k
0.1μF
0.1μF
37881 TA01a
37881f
1