LTC3499_15 Datasheet, PDF (1/16 Pages) Linear Technology – 750mA Synchronous Step-Up DC/DC Converters with Reverse-Battery Protection

LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
n _{Reverse-Battery Protection for DC/DC Converter}
and Load
n _{High Efficiency: Up to 94%}
n _{Generates 5V at 175mA from a 1.8V Input}
n _{Operates from 1.8V to 5.5V Input Supply}
n _{2V to 6V Adjustable Output Voltage}
n _{Inrush Current Controlled During Start-Up}
n _{Output Disconnnect in Shutdown}
n _{Low Noise 1.2MHz PWM Operation}
n _{Tiny External Components}
n _{Automatic Burst Mode}^® _{Operation (LTC3499)}
n _{Continuous Switching at Light Loads (LTC3499B)}
n _{Overvoltage Protection}
n _{8-Lead (3mm × 3mm × 0.75mm) DFN}
and MSOP Packages
APPLICATIONS
n _{Medical Equipment}
n _{Digital Cameras}
n _{MP3 Players}
n _{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.
DESCRIPTION
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.
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 de-
vices 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
V_IN
1.8V TO 3.2V ₊
100k
330pF
4.7µH
2.2µF
V_IN
SW
LTC3499
ON OFF SHDN
V_OUT
VC
FB
SS
GND
0.01µF
1M
324k
V_OUT
5V
175mA
10µF
3499 TA01
Battery Current vs V_IN
1.0
SHDN = 0V
V_OUT = 0V
0.5
0
–0.5
–1.0
–6
–4 –2
0
2
V_IN AND SW VOLTAGE (V)
4
6
3499 TA01b
3499fc
1