reduces quiescent current to 25µA, ensuring high efficiency
across the entire load range. An internal soft-start limits
inrush current during start-up.
Other features include a <1µA shutdown current and ro-
bust protection under short-circuit, thermal overload, and
output overvoltage conditions. The LTC3122 is offered in
both a low profile 12-lead (3mm × 4mm × 0.75 mm) DFN
package and a 12-lead thermally enhanced MSOP package.
n
n
n
n
n
V
IN
Range: 1.8V to 5.5V, 500mV After Start-Up
Output Voltage Range: 2.2V to 15V
800mA Output Current for V
IN
= 5V and V
OUT
= 12V
Output Disconnects from Input When Shut Down
Synchronous Rectification: Up to 95% Efficiency
Inrush Current Limit
Up to 3MHz Adjustable Switching Frequency
Synchronizable to External Clock
Selectable Burst Mode
®
Operation: 25µA I
Q
Output Overvoltage Protection
Soft-Start
<1µA I
Q
in Shutdown
12-Lead, 3mm × 4mm × 0.75mm Thermally
Enhanced DFN and MSOP Packages
applicaTions
n
n
n
n
RF Power
Piezo Actuators
Small DC Motors
12V Analog Rail From Battery, 5V, or Backup Capacitor
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Typical applicaTion
5V to 12V Synchronous Boost Converter with Output Disconnect
V
IN
5V
3.3µH
SW
V
IN
4.7µF
OFF ON
BURST PWM
SD
LTC3122
V
OUT
100nF
CAP
FB
V
C
SGND
4.7µF
PGND
210k
390pF
10pF
113k
1.02M
22µF
100
90
V
OUT
12V
800mA
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
3122 TA01a
Efficiency Curve
10
Burst Mode
OPERATION
1
POWER LOSS (W)
PWM
PWM/SYNC
RT
V
CC
PWM POWER LOSS
0.1
57.6k
0.1
10
1
100
LOAD CURRENT (mA)
0.01
1000
3122 TA01b
3122fa
For more information
www.linear.com/LTC3122
1
LTC3122
absoluTe MaxiMuM raTings
(Note 1)
V
IN
Voltage .................................................. –0.3V to 6V
V
OUT
Voltage ............................................ –0.3V to 18V
SW Voltage (Note 2) .................................. –0.3V to 18V
SW Voltage (Pulsed < 100ns) (Note 2)....... –0.3V to 19V
V
C
, RT Voltage .......................................... –0.3V to V
CC
CAP Voltage
V
OUT
< 5.7V ............................–0.3V to (V
OUT
+ 0.3V)
5.7V ≤ V
OUT
≤ 11.7V...... (V
OUT
– 6V) to (V
OUT
+ 0.3V)
V
OUT
> 11.7V .................................(V
OUT
– 6V) to 12V
All Other Pins ............................................... –0.3V to 6V
Operating Junction Temperature Range (Notes 3, 4)
LTC3122E/LTC3122I .......................... –40°C to 125°C
LTC3122H .......................................... –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
MSE Lead Temperature (Soldering, 10sec) ........... 300°C
pin conFiguraTion
TOP VIEW
SW
PGND
V
IN
PWM/SYNC
V
CC
RT
1
2
3
4
5
6
13
PGND
12 CAP
11 V
OUT
10 SGND
9
8
7
SD
FB
V
C
SW
PGND
V
IN
PWM/SYNC
V
CC
RT
1
2
3
4
5
6
TOP VIEW
12
11
10
9
8
7
CAP
V
OUT
SGND
SD
FB
V
C
13
PGND
DE PACKAGE
12-LEAD (4mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W (NOTE 5),
θ
JC
= 5°C/W
EXPOSED PAD (PIN 13) IS PGND,
MUST BE SOLDERED TO PCB FOR RATED THERMAL PERFORMANCE
MSE PACKAGE
12-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W (NOTE 5),
θ
JC
= 10°C/W
EXPOSED PAD (PIN 13) IS PGND,
MUST BE SOLDERED TO PCB FOR RATED THERMAL PERFORMANCE
orDer inForMaTion
LEAD FREE FINISH
LTC3122EDE#PBF
LTC3122IDE#PBF
LTC3122EMSE#PBF
LTC3122IMSE#PBF
LTC3122HMSE#PBF
TAPE AND REEL
LTC3122EDE#TRPBF
LTC3122IDE#TRPBF
LTC3122EMSE#TRPBF
LTC3122IMSE#TRPBF
LTC3122HMSE#TRPBF
PART MARKING*
3122
3122
3122
3122
3122
PACKAGE DESCRIPTION
12-Lead (4mm × 3mm) Plastic DFN
12-Lead (4mm × 3mm) Plastic DFN
12-Lead Plastic MSOP
12-Lead Plastic MSOP
12-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°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.
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/
2
3122fa
For more information
www.linear.com/LTC3122
LTC3122
elecTrical characTerisTics
PARAMETER
Minimum Start-Up Voltage
Input Voltage Range
Output Voltage Adjust Range
Feedback Voltage
Feedback Input Current
Quiescent Current, Shutdown
Quiescent Current, Active
Quiescent Current, Burst
N-channel MOSFET Switch Leakage Current
P-channel MOSFET Switch Leakage Current
N-channel MOSFET Switch On-Resistance
P-channel MOSFET Switch On-Resistance
N-channel MOSFET Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Switching Frequency
SYNC Frequency Range
PWM/SYNC Input High
PWM/SYNC Input Low
PWM/SYNC Input Current
CAP Clamp Voltage
V
CC
Regulation Voltage
Error Amplifier Transconductance
Error Amplifier Output Current
Soft-Start Time
SD
Input High
SD
Input Low
SD
Input Current
V
SD
= 5.5V
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 3). V
IN
= 3.6V, V
OUT
= 12V, RT = 57.6k unless otherwise noted.
CONDITIONS
V
OUT
= 0V
After V
OUT
≥ 2.2V
l
l
l
l
MIN.
0.5
2.2
1.178
TYP
1.7
MAX
1.8
5.5
15
UNITS
V
V
V
V
nA
µA
µA
µA
µA
µA
µA
Ω
Ω
1.202
1
0.01
500
25
10
1.225
50
1
700
40
20
30
70
V
FB
= 1.4V
V
SD
= 0V, V
OUT
= 0V, Not Including Switch Leakage
V
C
= 0V, Measured On V
IN
, Non-Switching
Measured on V
IN
, V
FB
> 1.4V
Measured on V
OUT
, V
FB
> 1.4V
V
SW
= 15V, V
OUT
= 15V, V
C
= 0V
V
SW
= 0V, V
OUT
= 15V, V
SD
= 0V
l
l
0.1
0.1
0.121
0.188
2.5
90
0.85
0.1
0.9 •V
CC
3.5
94
4.5
0
A
%
%
MHz
MHz
V
V
µA
V
V
µS
µA
ms
V
V
FB
= 1.0V
V
FB
= 1.4V
l
l
l
l
l
l
1
1.15
3
0.1•V
CC
V
PWM/SYNC
= 5.5V
V
OUT
> 6.1V, Referenced to V
OUT
V
IN
< 2.8V, V
OUT
> 5V
l
0.01
–5.2
4
70
–5.6
4.25
95
±25
10
1.6
1
–6.0
4.5
120
0.25
1
2
V
µA
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:
Voltage transients on the SW pin beyond the DC limit specified in
the Absolute Maximum Ratings are non-disruptive to normal operations
when using good layout practices, as shown on the demo board or
described in the data sheet or application notes.
Note 3:
The LTC3122 is tested under pulsed load conditions such that
T
A
≈ T
J
. The LTC3122E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3122I is guaranteed
to meet specifications over the full –40°C to 125°C operating junction
temperature range. The LTC3122H is guaranteed to meet specifications
over the full –40°C to 150°C operating junction range. 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
is the thermal impedance of the package.
Note 4:
The LTC3122 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 150°C when overtemperature shutdown is active.
Continuous operation above the specified maximum operating junction
temperature may result in device degradation or failure.
Note 5:
Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal impedance much higher than
the rated package specifications.
3122fa
For more information
www.linear.com/LTC3122
3
LTC3122
Configured as front page application unless otherwise specified.
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