LTC3458L
1.7A, 1.5MHz Synchronous
Step-Up DC/DC Converter
with Output Disconnect
DESCRIPTIO
The LTC
®
3458L is a high efficiency, current mode, fixed
frequency, step up DC/DC converter with true output
disconnect and inrush current limiting. The LTC3458L is
rated for up to 6V output and includes a 0.2Ω N-channel
MOSFET switch and a 0.3Ω P-channel MOSFET synchro-
nous rectifier. The LTC3458L 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 12µA 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 LTC3458L is available in a low profile (0.75mm),
4mm
×
3mm 12-pin DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 5481178, 6304066, 6580258, 5511131, 6498466
FEATURES
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High Efficiency: Up to 95%
Inrush Current Limiting and Output Disconnect
Programmable Output Voltages up to 6V
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
0.2Ω N-Channel and 0.3Ω P-Channel Switches
Ultralow Quiescent Currents: 12µA Sleep, <1µA in
Shutdown
12-Pin 4mm
×
3mm Thermally Enhanced DFN
Package
APPLICATIO S
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Point-of-Load Regulators
USB V
BUS
Power
Portable GPS
MP3 Players
TYPICAL APPLICATIO
7.4µH
Li-Ion to 5V at 1MHz
Li-Ion to 5V
OUT
Li Ion
3.1V TO 4.2V
V
IN
2.2µF
LTC3458L
GND/PGND
SHDN
SYNC
R
T
I
LIM
200k
84.5k
V
OUT
10pF
ON OFF
FB
COMP
0.01µF
SS
0.01µF
BURST
133k
560pF
3458L TA01a
SW
V
OUT
5V
750mA
1M
EFFICIENCY (%)
100
95
90
85
80
75
70
22µF
X5R
324k
33k
10pF
65
60
0.1
1
100
10
LOAD CURRENT (mA)
0.1
1000
3458L TA01b
U
U
U
1000
4.2V
IN
3.6 V
IN
POWER LOSS (mW)
3.1V
IN
3.6V
IN
100
10
POWER
LOSS
1
3458lf
1
LTC3458L
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
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
V
IN
, SS, SYNC Voltages ................................. –0.3 to 7V
BURST, SHDN, V
OUT
Voltages ....................... –0.3 to 7V
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 7V
Pulsed <100ns ........................................ –0.3V to 8V
ORDER PART
NUMBER
LTC3458LEDE
DE PART MARKING
3458L
DE 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
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
Error Amplifier Sink Current
SYNC Input High
SYNC Input Low
●
●
ELECTRICAL CHARACTERISTICS
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
6
1.25
1.25
50
30
10
1
3
3
5
5
UNITS
V
V
V
V
V
%
nA
µA
µA
µA
µA
mA
µA
µA
Ω
Ω
A
%
2
1.21
1.20
1.225
–4
1
12
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
0.2
0.3
V
OUT
= 5V
V
OUT
= 5V
R
ILIM
= 84.5k
V
IN
= 3.3V, f
OSC
= 1MHz
R
T
= 200k
●
●
●
●
1.7
80
0.85
2.1
90
0
1
60
7
7
1.15
1.5
0.35
2
U
%
MHz
µA/V
µA
µA
V
V
3458lf
W
U
U
W W
W
LTC3458L
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
SHDN Input High
SHDN Input Low
BURST Mode Peak Current (I
BURSTPEAK
)
BURST Threshold Voltage
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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
= 84.5k
CONDITIONS
●
●
ELECTRICAL CHARACTERISTICS
MIN
1.25
TYP
MAX
0.3
UNITS
V
V
A
V
0.55
1.10
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 3:
The LTC3458LE 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
BURSTPEAK
, I
ZERO
Currents
2200
2000
1800
1600
2.15
I
LIMIT
2.25
R
ILIMIT
= 84.5k
CURRENT (mA)
1200
1000
800
600
400
200
0
–200
2.0
2.5
3.0
3.5 4.0
V
IN
(V)
I
ZERO
I
BURSTPEAK
CURRENT (µA)
CURRENT (A)
1400
V
OUT
= 5V
L = 7.4µH
R
LIM
= 84.5k
4.5
Typical Burst Mode Threshold and
Hysteresis vs R
BURST
160
140
120
OUT OF
BURST
300
250
CURRENT (mA)
RT (kΩ)
100
80
60
40
INTO
BURST
CURRENT (mA)
20
0
50
100
150
200
R
BURST
(kΩ)
250
300
3458L G04
U W
5.0
3458L 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
2.05
1.95
5
I
VOUT
0
–40
5.5
1.85
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
–15
35
10
TEMPERATURE (°C)
60
85
3458L G03
3458L G02
Maximum Load Current in Burst
600
R
ILIM
= 84.5k
3.3V
OUT
200
150
100
50
0
1.5
5V
OUT
550
500
450
400
350
300
250
200
150
2.0
2.5
3.0
V
IN
(V)
3.5
4.0
4.5
3458L G05
Oscillator Programming Resistor
100
400
600
1000 1200
1400
800
OSCILLATOR FREQUENCY (kHz)
3458L G06
3458lf
3
LTC3458L
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency Accuracy
1.05
95
RT = 200k
93
1.03
FREQUENCY (MHz)
EFFICIENCY (%)
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
1600
1400
1.8 to 5.5V
IN
at 1MHz
R
ILIM
= 84.5k
5V
OUT
0.9
1.0
MAX LOAD CURRENT (mA)
1200
VOLTAGE (V)
0.8
VOLTAGE (V)
1000
800
600
400
3.3V
OUT
200
0
1.5 2.0
2.5
3.0 3.5 4.0
V
IN
(V)
4.5
5.0
5.5
0.5
–45 –30 –15
VOLTAGE (V)
4
U W
75
90
3458L G07
3458L G10
(T
A
= 25°C unless otherwise specified)
N-Channel and P-Channel R
DS(ON)
0.5
V
IN
= 3.3V
V
OUT
= 5V
0.3
P-CHANNEL
Efficiency vs Frequency
0.2
N-CHANNEL
89
0.1
87
V
IN
= 3.3V
V
OUT
= 5V at 200mA
L = 7.4µH
700
1100
1300
900
FREQUENCY (kHz)
1500
3458L G08
85
500
0
–40
–15
35
10
TEMPERATURE (°C)
60
85
3458L G09
SHDN Pin Threshold and
Hysteresis
1.5
1.4
1.3
OPERATING
1.2
1.1
1.0
0.6
0.9
SYNC Pin Threshold
0.7
SHUTDOWN
0 15 30 45 60
TEMPERATURE (°C)
75
90
0.8
–45 –30 –15
0 15 30 45 60
TEMPERATURE (°C)
75
90
3458L G11
3458L G12
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
3458L G13
3458lf
LTC3458L
TYPICAL PERFOR A CE CHARACTERISTICS
Fixed Frequency (FF)
Discontinuous Current
SW
1V/DIV
I
L
200mA/DIV
I
L
100mA/DIV
GND
0mA
V
IN
= 3.3V
V
OUT
= 5V
L = 7.4µH
500ns/DIV
V
IN
= 3.3V
V
OUT
= 5V
L = 7.4µH
500ns/DIV
0mA
Over-Current with 2A I
LIMIT
V
OUT
100mV/DIV
I
L
0.5A/DIV
SW
2V/DIV
0mA
V
IN
= 2.25V
V
OUT
= 5V
L = 7.4µH
R
ILIM
= 84.5k
1µs/DIV
I
L
200mA/DIV
V
IN
= 3.3V
V
OUT
= 5V
L = 7.4µH
C
OUT
= 22µF
C
FF
= 22pF
R
ILIM
= 84.5k
50µs/DIV
3458L G17
Burst Mode Operation Close-Up
V
OUT
100mV/DIV
SW
5V/DIV
I
L
200mA/DIV
V
IN
= 3.3V
3458L G18
2µs/DIV
V
OUT
= 5V
L = 7.4µH
C
OUT
= 22µF
C
FF
= 22pF*
R
ILIM
= 84.5k
*C
FF
: FEED FORWARD CAPACITOR CONECTED BETWEEN V
OUT
AND FB.
U W
(T
A
= 25°C unless otherwise specified)
Fixed Frequency (FF)
Continuous Current
SW
1V/DIV
3458L G14
3458L G15
Burst Mode Operation
SW
5V/DIV
0mA
3458L G16
Soft-Start into 20Ω Load
V
OUT
2V/DIV
V
IN
2V/DIV
0mA
SS
200mV/DIV
I
L
200mA/DIV
V
IN
= 3.3V
V
OUT
= 5V
L = 7.4µH
C
SS
= 0.1µF
2ms/DIV
3458L G19
3458lf
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