LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
DESCRIPTION
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The LTC®3499/LTC3499B are synchronous, fixed frequency
step-up DC/DC power converters with integrated reverse
battery protection that protect and disconnect the devices
and load when the battery polarity is reversed while
delivering high efficiency in a small (3mm × 3mm) DFN
package. True output disconnect eliminates inrush current
and allows zero load current in shutdown.
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Reverse-Battery Protection for DC/DC Converter
and Load
High Efficiency: Up to 94%
Generates 5V at 175mA from a 1.8V Input
Operates from 1.8V to 5.5V Input Supply
2V to 6V Adjustable Output Voltage
Inrush Current Controlled During Start-Up
Output Disconnnect in Shutdown
Low Noise 1.2MHz PWM Operation
Tiny External Components
Automatic Burst Mode® Operation (LTC3499)
Continuous Switching at Light Loads (LTC3499B)
Overvoltage Protection
8-Lead (3mm × 3mm × 0.75mm) DFN
and MSOP Packages
APPLICATIONS
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Medical Equipment
Digital Cameras
MP3 Players
Handheld Instruments
L, LT, LTC and LTM 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.
The devices feature an input voltage range of 1.8V to 5.5V
enabling operation from two alkaline or NiMH batteries. The
switching frequency is internally set at 1.2MHz allowing
the use of tiny surface mount inductors and capacitors.
A minimal number of external components are required
to generate output voltages ranging from 2V to 6V. The
LTC3499 features automatic Burst Mode operation to
increase efficiency at light loads, while the LTC3499B
features continuous switching at light loads.
The soft-start time is externally programmable through a
small capacitor. Anti-ring circuitry reduces EMI emissions
by damping the inductor in discontinuous mode. The
devices feature <1μA shutdown supply current, integrated
overvoltage protection and are available in both 8-pin
(3mm × 3mm) DFN and 8-pin MSOP packages.
TYPICAL APPLICATION
Two AA Cells to 5V Synchronous Boost Converter
4.7μH
+
1.0
SHDN = 0V
VOUT = 0V
2.2μF
VIN
SW
LTC3499
ON OFF
VOUT
SHDN
1M
VC
100k
330pF
VOUT
5V
175mA
10μF
FB
SS
GND
324k
BATTERY CURRENT (μA)
VIN
1.8V TO 3.2V
Battery Current vs VIN
0.5
0
–0.5
0.01μF
3499 TA01
–1.0
–6
–4
–2
0
2
4
VIN AND SW VOLTAGE (V)
6
3499 TA01b
3499fb
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