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 to be used
in high power boost applications.
A constant-frequency current mode architecture allows a
phase-lockable frequency of up to 850kHz. OPTI-LOOP
®
compensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
The LTC3788 features a precision 1.2V reference and dual
power good output indicators. A 4.5V to 38V input supply
range encompasses a wide range of system architectures
and battery chemistries.
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.
For a leaded 28-lead SSOP package with a fixed current
limit and one PGOOD output, without phase modulation
or a clock output, see the LTC3788-1 data sheet.
L,
LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP, PolyPhase and the Linear logo
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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Synchronous Operation for Highest Efficiency and
Reduced Heat Dissipation
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% 1.2V Reference Voltage
R
SENSE
or Inductor DCR Current Sensing
100% Duty Cycle Capability for Synchronous MOSFET
Low Quiescent Current: 125µA
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Selectable Current Limit
Adjustable Output Voltage Soft-Start
Power Good Output Voltage Monitors
Low Shutdown Current I
Q
: < 8μA
Internal LDO Powers Gate Drive from VBIAS or EXTV
CC
Thermally Enhanced Low Profile 32-Pin 5mm × 5mm
QFN Package
applicaTions
n
n
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Industrial
Automotive
Medical
Military
Typical applicaTion
3m
4.7µF
TG1 VBIAS INTV
CC
V
OUT
12V AT 5A
1.25µH
0.1µF
BOOST1
SW1
BG1
SENSE1
+
SENSE1
–
LTC3788
V
IN
4.5V TO 12V START-UP VOLTAGE
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
V
IN
4.7µF
TG2
4m
220µF
100
Efficiency and Power Loss
vs Output Current
10000
90
BOOST2
SW2
BG2
SENSE2
+
SENSE2
–
PGND
3.3µH
0.1µF
V
OUT
24V AT 3A
EFFICIENCY (%)
80
70
60
50
40
30
1000
POWER LOSS (mW)
100
10
110k
VFB1
VFB2
232k
220µF
12.1k
15nF
2.7k
FREQ
PLLIN/MODE
ITH1 SS1 SGND SS2 ITH2
100pF
0.1µF
220pF
V
IN
= 12V
1
V
OUT
= 24V
10
Burst Mode OPERATION
FIGURE 9 CIRCUIT
0
0.1
0.00001 0.0001 0.001 0.01
0.1
1
10
OUTPUT CURRENT (A)
20
220µF
3788 TA01b
15nF
8.66k
12.1k
3788 TA01a
0.1µF
3788fc
1
LTC3788
absoluTe MaxiMuM raTings
(Notes 1, 3)
pin conFiguraTion
TOP VIEW
SENSE1
+
PGOOD1
VBIAS ........................................................ –0.3V to 40V
BOOST1, BOOST2 ...................................... –0.3V to 76V
SW1, SW2.................................................. –0.3V to 70V
RUN1, RUN2 ................................................ –0.3V to 8V
Maximum Current Sourced into Pin
from Source > 8V .............................................100µA
PGOOD1, PGOOD2, 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
I
LIM
, SS1, SS2, ITH1, ITH2, FREQ,
PHASMD, VFB1, VFB2...........................–0.3V to INTV
CC
Operating Junction Temperature Range ....–40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
VFB1
ITH1
SW1
SW2
ILIM
SS1
32 31 30 29 28 27 26 25
SENSE1
–
1
TG1
24 BOOST1
23 BG1
22 VBIAS
21 PGND
20 EXTV
CC
19 INTV
CC
18 BG2
17 BOOST2
TG2
FREQ 2
PHASMD 3
CLKOUT 4
PLLIN/MODE 5
SGND 6
RUN1 7
RUN2 8
9 10 11 12 13 14 15 16
VFB2
ITH2
SS2
SENSE2
–
SENSE2
+
PGOOD2
33
GND
UH PACKAGE
32-LEAD (5mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3788EUH#PBF
LTC3788IUH#PBF
TAPE AND REEL
LTC3788EUH#TRPBF
LTC3788IUH#TRPBF
PART MARKING*
3788
3788
PACKAGE DESCRIPTION
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
elecTrical characTerisTics
SYMBOL
VBIAS
V
FB1,2
I
FB1,2
V
REFLNREG
PARAMETER
Chip Bias Voltage Operating Range
Regulated Feedback Voltage
Feedback Current
Reference Line Voltage Regulation
Main Control Loop
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
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