Document
U U
FEATURES
■ 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 5VOUT ■ Ultralow Quiescent Currents: 15μA Sleep, <1μA in
Shutdown ■ 3mm × 4mm Thermally Enhanced DFN Package
U APPLICATIO S
■ Point-of-Load Regulators ■ USB VBUS Power ■ LCD Bias ■ OLED Displays
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 synchronous 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 synchronized to an external clock.
Quiescent current is only 15μA during Burst Mode operation maximizing battery life in portable applications. The Burst Mode current threshold, peak current limit, and softstart 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.
TYPICAL APPLICATIO
USB to 7V at 1MHz
COEV 10μH DQ7545
USB 4.35V to 5.25V
2.2μF
VIN
SW
LTC3458
GND/PGND
VOUT
ON OFF
SHDN
FB
SYNC
RT
ILIM 200k 124k
COMP
0.01μF
SS
BURST
0.01μF
133k
10pF
1.5M
VOUT 7V
500mA
33k 10pF 560pF
316k 22μF X5R
3458 TA01a
EFFICIENCY
POWER LOSS (mW)
USB to 7VOUT
100
1000
95
5.25VIN
90 4.35VIN
85
10
POWER LOSS 80
75
70 0.1
1
10
100
LOAD CURRENT (mA)
0.1 1000
3458 TA01b
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LTC3458
U WW W
ABSOLUTE AXI U RATI GS
(Note 1)
VIN, SS, SYNC Voltages ................................. –0.3 to 7V BURST, SHDN, VOUT 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
PIN CONFIGURATION
TOP VIEW
SW 1
12 VOUT
VIN 2
11 BURST
SYNC 3
10 SS
13
SHDN 4
9 GND
ILIM 5 RT 6
8 COMP 7 FB
DE12 PACKAGE 12-LEAD (4mm × 3mm) PLASTIC DFN
EXPOSED PAD IS PGND (PIN 13), MUST BE SOLDERED TO PCB TJMAX = 125°C, θJA = 45°C/W
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL
PART MARKING PACKAGE DESCRIPTION
LTC3458EDE#PBF LTC3458EDE#TRPBF
3458
12-Lead (4mm x 3mm) Plastic DFN
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/
TEMPERATURE RANGE –40ºC to 85ºC
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, VOUT = 5V, RT = 200k, unless otherwise noted.
PARAMETER Minimum VIN 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
CONDITIONS TA = 0°C to 85°C TA = –40°C to 0°C
0°C to 85°C, VOUT = 3.3V –40°C to 0°C Below Feedback Voltage VFB = 1.23V VIN Current at 3.3V VOUT Current at 5V VIN Current at 3.3V VOUT Current at 0V VIN Current Switching
VOUT = 5V VOUT = 5V RILIM = 124k VIN = 3.3V, fOSC = 1MHz
RT = 200k
MIN TYP MAX UNITS
1.4
1.5
V
1.4
1.7
V
● 2.0
7.5
V
1.21 1.23 1.25
V
1.20
1.25
V
–4%
V
1
50
nA
15
30
μA
5
10
μA
0.5
1
μA
1
3
μA
1
3
mA
●
0.05
5
μA
●
0.05
5
μA
0.3
Ω
0.4
Ω
● 1.4
1.6
A
● 80
90
%
●
0
%
● 0.85
1
1.15
MHz
100
μA/V
7
μA
3458fa
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LTC3458
ELECTRICAL CHARACTERISTICS The ● denotes the specificat.