LTC3458
1.4A, 1.5MHz Synchronous
Step-Up DC/DC Converter
with Output Disconnect
DESCRIPTIO
The LTC
®
3458 is a high efficiency, current mode, fixed
frequency, step up DC/DC converter with true output
disconnect and inrush current limiting. The LTC3458 is
rated for a 7.5V output and includes a 0.3Ω N-channel
MOSFET switch and a 0.4Ω P-channel MOSFET synchro-
nous rectifier. The LTC3458 is well suited for battery
powered applications and includes programmable output
voltage, switching frequency and loop compensation. The
oscillator frequency can be set up to 1.5MHz or synchro-
nized to an external clock.
Quiescent current is only 15μA during Burst Mode opera-
tion maximizing battery life in portable applications. The
Burst Mode current threshold, peak current limit, and soft-
start are externally programmable. Other features include
<1μA shutdown current, antiringing control, and thermal
limit. The LTC3458 is available in a low profile (0.75mm),
3mm
×
4mm 12-pin DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Burst Mode is a registered trademark of Linear Technology Corporation.
FEATURES
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■
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High Efficiency: Up to 93%
Inrush Current Limiting and Output Disconnect
Programmable Output Voltages up to 7.5V
1.5V to 6V Input Range
Programmable/Synchronizable Fixed Frequency
Operation up to 1.5MHz
Programmable Automatic Burst Mode
®
Operation
Current Mode Control with Programmable Soft-Start
Period and Peak Current Limit
700mA at 7V from 5V Input
0.3Ω N-Channel and 0.4Ω P-Channel 1.4A Switches
at 5V
OUT
Ultralow Quiescent Currents: 15μA Sleep, <1μA in
Shutdown
3mm
×
4mm Thermally Enhanced DFN Package
Point-of-Load Regulators
USB V
BUS
Power
LCD Bias
OLED Displays
APPLICATIO S
■
■
■
■
TYPICAL APPLICATIO
COEV
10μH
DQ7545
USB to 7V at 1MHz
USB to 7V
OUT
100
V
IN
2.2μF
LTC3458
GND/PGND
SHDN
SYNC
R
T
I
LIM
200k
124k
V
OUT
10pF
ON OFF
FB
COMP
0.01μF
SS
0.01μF
BURST
133k
560pF
3458 TA01a
SW
V
OUT
7V
500mA
1.5M
USB
4.35V to 5.25V
EFFICIENCY
316k
33k
10pF
22μF
X5R
75
70
0.1
0.1
1000
3458 TA01b
U
U
U
1000
95
90
85
5.25V
IN
POWER LOSS (mW)
4.35V
IN
10
POWER LOSS
80
1
10
100
LOAD CURRENT (mA)
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LTC3458
ABSOLUTE
AXI U RATI GS
(Note 1)
V
IN
, SS, SYNC Voltages ................................. –0.3 to 7V
BURST, SHDN, V
OUT
Voltages ....................... –0.3 to 8V
Operating Temperature Range
(Notes 2, 3) .........................................–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
SW Voltage
DC ........................................................... –0.3V to 8V
Pulsed <100ns ...................................... –0.3V to 10V
ORDER INFORMATION
LEAD FREE FINISH
LTC3458EDE#PBF
TAPE AND REEL
LTC3458EDE#TRPBF
PART MARKING
3458
PACKAGE DESCRIPTION
12-Lead (4mm x 3mm) Plastic DFN
TEMPERATURE RANGE
–40ºC to 85ºC
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC for information on nonstandard 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/
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, V
OUT
= 5V, R
T
= 200k, unless otherwise noted.
PARAMETER
Minimum V
IN
Operating Voltage
Output Voltage Adjust Range
Feedback Voltage
Undervoltage (Exit Burst Mode Operation)
Feedback Input Current
Quiescent Current - Burst Mode Operation
Quiescent Current - Shutdown
Quiescent Current - Active
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
Fixed NMOS Current Limit
Maximum Duty Cycle
Minimum Duty Cycle
Frequency Accuracy
Error Amplifier Transconductance
Error Amplifier Source Current
R
T
= 200k
V
OUT
= 5V
V
OUT
= 5V
R
ILIM
= 124k
V
IN
= 3.3V, f
OSC
= 1MHz
●
●
●
●
ELECTRICAL CHARACTERISTICS
2
U
W W
W
PIN CONFIGURATION
TOP VIEW
SW
V
IN
SYNC
SHDN
I
LIM
R
T
1
2
3
13
4
5
6
9
8
7
GND
COMP
FB
12 V
OUT
11 BURST
10 SS
DE12 PACKAGE
12-LEAD (4mm
×
3mm) PLASTIC DFN
EXPOSED PAD IS PGND (PIN 13),
MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 45°C/W
CONDITIONS
T
A
= 0°C to 85°C
T
A
= –40°C to 0°C
●
MIN
TYP
1.4
1.4
MAX
1.5
1.7
7.5
1.25
1.25
50
30
10
1
3
3
5
5
UNITS
V
V
V
V
V
V
nA
μA
μA
μA
μA
mA
μA
μA
Ω
Ω
A
%
2.0
1.21
1.20
1.23
–4%
1
15
5
0.5
1
1
0°C to 85°C, V
OUT
= 3.3V
–40°C to 0°C
Below Feedback Voltage
V
FB
= 1.23V
V
IN
Current at 3.3V
V
OUT
Current at 5V
V
IN
Current at 3.3V
V
OUT
Current at 0V
V
IN
Current Switching
●
●
0.05
0.05
0.3
0.4
1.4
80
0.85
1.6
90
0
1
100
7
1.15
%
MHz
μA/V
μA
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LTC3458
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, V
OUT
= 5V, R
T
= 200k, unless otherwise noted.
PARAMETER
Error Amplifier Sink Current
SYNC Input High
SYNC Input Low
SHDN Input High
SHDN Input Low
BURST Mode Peak Current
BURST Threshold Voltage
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:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
R
ILIM
= 124k
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
1.5
TYP
7
MAX
UNITS
μA
V
0.35
1.25
0.3
0.4
1.10
V
V
V
A
V
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 3:
The LTC3458 is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
TYPICAL PERFOR A CE CHARACTERISTICS
I
LIMIT
, I
BURST
, T
ZERO
Currents
2000
1800
1600
1400
I
LIMIT
1,7
1.8
R
ILIMIT
= 124k
CURRENT (mA)
1000
800
600
400
200
0
–200
2.0
I
ZERO
I
BURST PEAK
CURRENT (A)
1200
CURRENT (μA)
V
OUT
= 7V
L = 10μH
R
ILIM
= 124k
2.5
3.0
3.5 4.0
V
IN
(V)
4.5
Typical Burst Mode Threshold and
Hysteresis vs R
BURST
160
140
200
120
OUT OF
BURST
250
CURRENT (mA)
RT (kΩ)
100
80
60
40
20
0
50
INTO
BURST
CURRENT (mA)
100
150
200
R
BURST
(kΩ)
U W
5.0
5.5
3458 G01
(T
A
= 25°C unless otherwise specified)
Burst Mode Quiescent Current
20
V
IN
= 3.3V
V
OUT
= 5V
15
I
VIN
10
Current Limit Accuracy
1.6
1.5
5
I
VOUT
0
–40
1.4
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
–15
35
10
TEMPERATURE (°C)
60
85
3458 G03
3458 G02
Maximum Load Current in Burst
600
R
ILIM
= 124k
3.3V
OUT
5V
OUT
7.5V
OUT
550
500
450
150
400
350
300
250
50
200
150
Oscillator Programming Resistor
100
250
300
3458 G04
0
1.5
2.0
2.5
3.0
3.5
V
IN
(V)
4.0
4.5
5.0 5.5
3458 G05
100
400
600
1000 1200
1400
800
OSCILLATOR FREQUENCY (kHz)
3458 G06
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LTC3458
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency Accuracy
1.05
95
RT = 200k
93
EFFICIENCY (%)
1.03
FREQUENCY (MHz)
1.01
91
R
DS(ON)
(Ω)
0.99
0.97
0.95
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
Maximum Load Current
1200
1000
MAX LOAD CURRENT (mA)
1.8 to 5.5V
IN
at 700kHz
R
ILIM
= 124k
5V
OUT
0.9
VOLTAGE (V)
0.8
VOLTAGE (V)
800
600
3.3V
OUT
7.5V
OUT
400
200
0
1.5 2.0
2.5
3.0 3.5 4.0
V
IN
(V)
4.5
VOLTAGE (V)
4
U W
75
90
3458 G07
(T
A
= 25°C unless otherwise specified)
N-Channel and P-Channel R
DS(ON)
0.5
V
IN
= 3.3V
V
OUT
= 5V
0.4
P-CHANNEL
Efficiency vs Frequency
V
IN
= 3.3V
V
OUT
= 5V at 100mA
0.3
N-CHANNEL
89
0.2
87
0.1
85
500
700
1100
1300
900
FREQUENCY (kHz)
1500
3458 G08
0
–40
–15
35
10
TEMPERATURE (°C)
60
85
3458 G09
SHDN Pin Threshold and
Hysteresis
1.0
1.5
1.4
1.3
OPERATING
1.2
1.1
1.0
0.6
0.9
SYNC Pin Threshold
0.7
SHUTDOWN
5.0
5.5
0.5
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
0.8
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3458 G12
3458 G10
3458 G11
FB Voltage
1.25
1.24
1.23
1.22
1.21
1.20
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3458 G13
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LTC3458
TYPICAL PERFOR A CE CHARACTERISTICS
Fixed Frequency (FF)
Discontinuous Current
Fixed Frequency (FF)
Continuous Current
SW
2V/DIV
SW
2V/DIV
I
L
100mA/DIV
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
200ns/DIV
Over-Current with 1.5A I
LIMIT
V
OUT
100mV/DIV
SW
2V/DIV
SW
5V/DIV
I
L
0.5A/DIV
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
R
ILIM
= 133k
Burst Mode Operation Close-Up
V
OUT
100mV/DIV
SW
5V/DIV
I
L
200mA/DIV
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
C
OUT
= 22μF
C
FF
= 22pF
2μs/DIV
U W
1μs/DIV
I
L
200mA/DIV
0mA
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
200ns/DIV
0mA
Burst Mode Operation
I
L
200mA/DIV
0mA
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
C
OUT
= 22μF
C
FF
= 22pF
50μs/DIV
0mA
Soft-Start into 50Ω Load
V
OUT
2V/DIV
V
IN
2V/DIV
SS
200mV/DIV
I
L
200mA/DIV
0mA
V
IN
= 3.3V
V
OUT
= 7V
L = 10μH
5ms/DIV
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