reduces power losses and eases thermal requirements,
allowing the LTC3786 to be used in 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 LTC3786 can operate from
an input supply as low as 2.5V after start-up. The 55µA
no-load quiescent current extends operating run time in
battery-powered systems.
The operating frequency can be set for a 50kHz to 900kHz
range or synchronized to an external clock using the
internal PLL. The LTC3786 also features a precision 1.2V
reference and a power good output indicator. The SS pin
ramps the output voltage during start-up. The PLLIN/MODE
pin selects among Burst Mode
®
operation, pulse-skipping
mode or continuous inductor current mode at light loads.
All registered trademarks and trademarks are the property of their respective owners.
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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 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: 55µA
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 5.4V LDO for Gate Drive Supply
Thermally Enhanced 16-Pin 3mm
×
3mm QFN and
MSOP Packages
APPLICATIONS
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Industrial and Automotive Power Supplies
Automotive Start-Stop Systems
Medical Devices
High Voltage Battery-Powered Systems
TYPICAL APPLICATION
12V to 24V/5A Synchronous Boost Converter
V
IN
4.5V TO 24V
VBIAS
SENSE
+
LTC3786
SENSE
PGOOD
PLLIN/MODE
RUN
FREQ
TG
SS
8.66k
220pF
12.1k
232k
ITH
–
Efficiency and Power Loss
vs Load Current
100
10000
BURST
EFFICIENCY
90
80
EFFICIENCY (%)
70
60
50
40
30
V
IN
= 12V
1
V
OUT
= 24V
Burst Mode OPERATION
10
FIGURE 8 CIRCUIT
0
0.1
0.1
1
10
0.00001 0.0001 0.001 0.01
OUTPUT CURRENT (A)
20
3786 TA01a
4m
220µF
3.3µH
BURST
LOSS
1000
POWER LOSS (mW)
100
0.1µF
15nF
SW
BOOST
BG
0.1µF
220µF
V
OUT
24V
5A
10
VFB
INTV
CC
GND
4.7µF
3786 TA01b
3786fc
For more information
www.linear.com/LTC3786
1
LTC3786
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 3)
VBIAS ........................................................ –0.3V to 40V
BOOST ........................................................–0.3V to 71V
SW ............................................................. –0.3V to 65V
RUN ............................................................. –0.3V to 8V
Maximum Current Sourced into Pin
from Source >8V ..............................................100µA
PGOOD, PLLIN/MODE .................................. –0.3V to 6V
INTV
CC
, (BOOST – SW) ............................... –0.3V to 6V
SENSE
+
, SENSE
–
........................................ –0.3V to 40V
SENSE
+
– SENSE
–
..................................... –0.3V to 0.3V
SS, ITH, FREQ, VFB............................... –0.3V to INTV
CC
Operating Junction Temperature Range (Notes 2, 3)
LTC3786E, LTC3786I ..........................–40°C to 125°C
LTC3786H ...........................................–40°C to 150°C
Storage Temperature Range ....................–65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSE Package Only ............................................ 300°C
PIN CONFIGURATION
TOP VIEW
VFB
SENSE
+
SENSE
–
ITH
SS
PLLIN/MODE
FREQ
RUN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
PGOOD
SW
TG
BOOST
VBIAS
INTV
CC
BG
GND
SW 1
PGOOD 2
VFB 3
SENSE
+
16 15 14 13
12 BG
17
GND
11 GND
10 RUN
9
5
SENSE
–
6
ITH
7
SS
8
PLLIN/
MODE
FREQ
17
GND
4
MSE PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
UD PACKAGE
16-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 150°C,
θ
JA
= 68°C/W,
θ
JC
= 4.2°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3786EMSE#PBF
LTC3786IMSE#PBF
LTC3786HMSE#PBF
LTC3786EUD#PBF
LTC3786IUD#PBF
LTC3786HUD#PBF
TAPE AND REEL
LTC3786EMSE#TRPBF
LTC3786IMSE#TRPBF
LTC3786HMSE#TRPBF
LTC3786EUD#TRPBF
LTC3786IUD#TRPBF
LTC3786HUD#TRPBF
http://www.linear.com/product/LTC3786#orderinfo
PART MARKING*
3786
3786
3786
LFXW
LFXW
LFXW
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–40°C to 125°C
–40°C to 125°C
–40°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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
INTV
CC
TOP VIEW
BOOST
VBIAS
TG
2
3786fc
For more information
www.linear.com/LTC3786
LTC3786
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
I
TH
= 1.2V (Note 4)
(Note 4)
V
BIAS
= 6V to 38V
(Note 4)
Measured in Servo Loop;
∆I
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
∆I
TH
Voltage = 1.2V to 2V
I
TH
= 1.2V
l
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
BIAS
= 12V, unless otherwise noted (Note 2).
CONDITIONS
MIN
4.5
1.188
1.200
±5
0.002
0.01
–0.01
2
0.8
55
8
l
l
l
TYP
MAX
38
1.212
±50
0.02
0.1
–0.1
UNITS
V
V
nA
%/V
%
%
mmho
mA
µA
µA
V
V
V
mV
µA
µA
Main Control Loop
g
m
I
Q
Error Amplifier Transconductance
Input DC Supply Current
(Note 5)
Pulse-Skipping or Forced Continuous Mode
RUN = 5V; V
FB
= 1.25V (No Load)
Sleep Mode
RUN = 5V; V
FB
= 1.25V (No Load)
Shutdown
RUN = 0V
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
SENSE Pins Common Mode Range (BOOST
Converter Input Supply Voltage V
IN
)
SENSE
+
Pin Current
SENSE
–
Pin Current
Top Gate Rise Time
Top Gate Fall Time
Bottom Gate Rise Time
Bottom Gate Fall Time
Top Gate Pull-Up Resistance
Top Gate Pull-Down Resistance
Bottom Gate Pull-Up Resistance
Bottom Gate Pull-Down Resistance
Top Gate Off to Bottom Gate On Switch-On
Delay Time
Bottom Gate Off to Top Gate On Switch-On
Delay Time
Maximum BG Duty Factor
Minimum BG On-Time
(Note 7)
C
LOAD
= 3300pF (Each Driver)
C
LOAD
= 3300pF (Each Driver)
V
FB
= 1.1V
V
FB
= 1.1V
C
LOAD
= 3300pF (Note 6)
C
LOAD
= 3300pF (Note 6)
C
LOAD
= 3300pF (Note 6)
C
LOAD
= 3300pF (Note 6)
V
RUN
> 1.28V
V
RUN
< 1.28V
V
SS
= 0V
V
FB
= 1.1V
l
80
20
4.3
1.38
UVLO
V
RUN
V
RUNHYS
I
RUNHYS
I
RUN
I
SS
V
SENSE(MAX)
V
SENSE(CM)
I
SENSE+
I
SENSE–
t
r(TG)
t
f(TG)
t
r(BG)
t
f(BG)
R
UP(TG)
R
DN(TG)
R
UP(BG)
R
DN(BG)
t
D(TG/BG)
t
D(BG/TG)
DF
MAXBG
t
ON(MIN)
V
INTVCC
Ramping Up
V
INTVCC
Ramping Down
V
RUN
Rising
3.6
1.18
4.1
3.8
1.28
100
4.5
0.5
7
68
2.5
10
75
13
82
38
µA
mV
V
µA
µA
ns
ns
ns
ns
200
20
20
20
20
1.2
1.2
1.2
1.2
80
80
96
110
300
±1
ns
ns
%
ns
3786fc
For more information
www.linear.com/LTC3786
3
LTC3786
ELECTRICAL CHARACTERISTICS
SYMBOL
V
INTVCC(VIN)
V
LDO
INT
f
PROG
f
LOW
f
HIGH
f
SYNC
PGOOD Output
V
PGL
I
PGOOD
V
PG
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative
Hysteresis
V
FB
Ramping Positive
Hysteresis
PGOOD Going High to Low
V
SW
= 12V; V
BOOST
– V
SW
= 4.5V;
FREQ = 0V, Forced Continuous or
Pulse-Skipping Mode
–12
8
–10
2.5
10
2.5
25
85
0.2
0.4
±1
–8
12
V
µA
%
%
%
%
µs
µA
PARAMETER
Internal V
CC
Voltage
INTV
CC
Load Regulation
Programmable Frequency
INTV
CC
Linear Regulator
6V < VBIAS < 38V
I
CC
= 0mA to 50mA
R
FREQ
= 25k
R
FREQ
= 60k
R
FREQ
= 100k
V
FREQ
= 0V
V
FREQ
= INTV
CC
PLLIN/MODE = External Clock
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
BIAS
= 12V, unless otherwise noted (Note 2).
CONDITIONS
MIN
5.2
TYP
5.4
0.5
105
400
760
350
535
MAX
5.6
2
UNITS
V
%
kHz
kHz
kHz
kHz
kHz
kHz
Oscillator and Phase-Locked Loop
335
320
485
75
465
380
585
850
Lowest Fixed Frequency
Highest Fixed Frequency
Synchronizable Frequency
t
PGOOD(DELAY)
I
BOOST
PGOOD Delay
BOOST Charge Pump Available
Output Current
BOOST Charge Pump
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3786 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3786E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3786I is guaranteed over the –40°C to 125°C operating junction
temperature range. The LTC3786H is guaranteed over the –40°C to 150°C
operating temperature range. High temperatures degrade operating
lifetimes; operating lifetime is derated for junction temperatures greater
than 125ºC. Note that the maximum ambient temperature consistent
with these specifications is determined by specific operating conditions
in conjunction with board layout, the rated package thermal impedance
and other environmental factors. The junction temperature (T
J
in °C) is
calculated from the ambient temperature (T
A
in °C) and power dissipation
(P
D
in Watts) according to the formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
= 68°C for the QFN package and
θ
JA
= 40°C for the MSOP
package.
Note 3:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 4:
The LTC3786 is tested in a feedback loop that servos V
FB
to the
output of the error amplifier while maintaining I
TH
at the midpoint of the
current limit range.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
see Minimum On-Time Considerations in the Applications
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