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.
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 LTC3788-1 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.
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 leadless 32-pin QFN package with additional features
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
,
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.
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)
Adjustable Output Voltage Soft-Start
Power Good Output Voltage Monitor
Low Shutdown Current I
Q
: < 8μA
Internal LDO Powers Gate Drive from VBIAS or EXTV
CC
Available in a Narrow SSOP Package
APPLICATIONS
n
n
n
n
Industrial
Automotive
Medical
Military
TYPICAL APPLICATION
3mΩ
4.7μF
TG1 VBIAS INTV
CC
V
OUT
12V AT 5A
1.25μH
0.1μF
SW1
BG1
SENSE1
LTC3788-1
+
V
IN
4.5V TO 12V START-UP VOLTAGE
OPERATES THROUGH TRANSIENTS DOWN TO 2.5V
V
IN
4.7μF
TG2
4mΩ
220μF
100
Efficiency and Power Loss
vs Load Current
10000
90
BOOST1
BOOST2
SW2
BG2
3.3μH
0.1μF
V
OUT
24V AT 3A
EFFICIENCY (%)
80
70
60
50
40
30
1000
POWER LOSS (mW)
100
SENSE2
+
SENSE2
–
PGND
SENSE1
–
10
110k
VFB1
VFB2
FREQ
PLLIN/MODE
ITH1 SS1 SGND SS2 ITH2
220μF
12.1k
15nF
2.7k
100pF
0.1μF
220pF
0.1μF
15nF
8.66k
232k
V
IN
= 12V
1
V
OUT
= 24V
10
Burst Mode OPERATION
FIGURE 9 CIRCUIT
0.1
0
0.00001 0.0001 0.001 0.01
0.1
1
10
OUTPUT CURRENT (A)
20
220μF
37881 TA01b
12.1k
37881 TA01a
37881fa
1
LTC3788-1
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 3)
PIN CONFIGURATION
TOP VIEW
ITH1
VFB1
SENSE1
+
SENSE1
–
FREQ
PLLIN/MODE
SGND
RUN1
RUN2
SENSE2
+
1
2
3
4
5
6
7
8
9
28 SS1
27 PGOOD1
26 SW1
25 TG1
24 BOOST1
23 BG1
22 VBIAS
21 PGND
20 EXTV
CC
19 INTV
CC
18 BG2
17 BOOST2
16 TG2
15 SW2
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, 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
SS1, SS2, ITH1, ITH2, FREQ,
VFB1, VFB2 ........................................... –0.3V to INTV
CC
Operating Junction Temperature Range ... –40°C to 125°C
Storage Temperature Range................... –65°C to 125°C
Lead Temperature (Soldering, 10 seconds) .......... 300°C
SENSE2
–
10
11
VFB2 12
ITH2 13
SS2 14
GN PACKAGE
28-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 80°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3788EGN-1#PBF
LTC3788IGN-1#PBF
TAPE AND REEL
LTC3788EGN-1#TRPBF
LTC3788IGN-1#TRPBF
PART MARKING*
LTC3788GN-1
LTC3788GN-1
PACKAGE DESCRIPTION
28-Lead Plastic SSOP
28-Lead Plastic SSOP
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.
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
VFB1,2
IFB1,2
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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