LTC3125_15 Datasheet, PDF (1/18 Pages) Linear Technology – 1.2A Synchronous Step-Up DC/DC Converter with Input Current Limit

LTC3125
1.2A Synchronous Step-Up
DC/DC Converter with
Input Current Limit
FEATURES
n _{Programmable Average Input Current Limit}
n _{5% Input Current Accuracy}
n _{200mA to 1000mA Program Range}
n _{VIN: 1.8V to 5.5V, VOUT: 2V to 5.25V}
n _{Supports High Current GSM/GPRS Load Burst}
n _{VIN > VOUT Operation}
n _{1.6MHz Fixed Frequency Operation}
n _{Internal Current Sense Resistor}
n _{1.2A Peak Current Limit}
n _{Up to 93% Efficiency}
n _{Output Disconnect in Shutdown}
n _Soft-Start
n _{Low Quiescent Current Burst Mode}^® _Operation
n _{Available in 2mm × 3mm × 0.75mm DFN Package}
APPLICATIONS
n _{GSM/GPRS PCMCIA/CompactFlash PC Card Modems}
n _{Wireless Emergency Locators}
n _{Portable Radios}
n _{Supercap Chargers}
DESCRIPTION
The LTC^®3125 is a high efficiency, synchronous step-up
DC/DC converter with an accurate programmable average
input current limit. The resistor programmable average
input current limit is 5% accurate at 500mA and is suitable
for a wide variety of applications. In mobile computing,
GSM and GPRS cards demand high current pulses well
beyond the capability of the PC Card and CompactFlash
slots. The LTC3125 in concert with a reservoir capacitor,
keeps the slot power safely within its capabilities providing
a high performance and simple solution.
Synchronous rectification produces high efficiency while
the 1.6MHz switching frequency minimizes the solution
footprint. The current mode PWM design is internally com-
pensated. Output disconnect allows the load to discharge in
shutdown, while also providing inrush current limiting.
Other features include a <1μA shutdown current, short-
circuit and thermal overload protection. The LTC3125 is
offered in a low profile 0.75mm × 2mm × 3mm package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
PCMCIA/CompactFlash (3.3V/500mA Max),
4V GSM Pulsed Load
2.2μH
V_IN
3.3V
500mA
10μF
CER
OFF ON
CS
SW
V_IN
V_OUT
LTC3125
SHDN
44.2k
PROG
FB
GND
1.24M
536k
V_OUT
4V
2A PULSED LOAD
2200μF
s2
TANT
3125 TA01a
Efficiency vs Load Current
100
90
80
70
60
50
40
30
20
10
0
0.001
1
0.1
0.01
V_OUT = 4V
V_IN = 3.3V
V_IN = 2.4V
0.001
0.01
0.1
1
LOAD CURRENT (A)
3125 TA01b
3125fa
1