LT1500/LT1501
Adaptive-Frequency
Current Mode Switching Regulators
FEATURES
s Low Noise Adaptive-Frequency Current Mode
Operation Avoids Low Frequency Noise at
Most Load Currents
s Can Be Externally Synchronized (LT1500)
s Micropower Quiescent Current: 200µA
s Shutdown Current: 8µA Typ
s Internal Loop Compensation
s Low-Battery Comparator Active in Shutdown
s Minimum Input Voltage: 1.8V Typ
s Additional Negative Voltage Feedback Pin (LT1500)
s Up to 500kHz Switching Frequency
s Uses Low Profile, Low Cost Surface Mount Inductors
U
APPLICATIONS
s Portable Instrumentation
s Battery Operated Systems
s PDA’s
s Standby Power
DESCRIPTION
The LT®1500 is an adaptive-frequency current mode step-
up switching regulator with an internal power switch that
is rated up to 700mA. In contrast to pulse skipping
switching regulators, the LT1500 uses a current mode
topology that provides lower noise operation and im-
proved efficiency. Only at very light loads is Burst ModeTM
activated to give high efficiency and micropower opera-
tion. High switching frequency (up to 500kHz) allows very
small inductors to be used, along with ceramic capacitors
if desired.
The LT1500 operates with input voltages from 1.8V to 15V
and has only 200µA operating current dropping to 8µA in
shutdown. A low-battery comparator is included which
stays alive in shutdown. A second output feedback pin
with negative polarity allows negative output voltages to
be regulated when the switcher is connected up as a Cuk
or a flyback converter.
Two package types are available. The LT1500 comes in a
14-pin SO package, with two options available for fixed
output (3.3V or 5V) or adjustable operation. A reduced
feature part, the LT1501, comes in the smaller 8-pin SO
package with internal frequency compensation. It is also
available in adjustable and fixed output voltage versions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
2-Cell to 5V Converter
D1
22µH† MBR0520L
5V, 200mA
2 EACH
NiCd OR
ALKALINE
CELLS
301k
1%
+ 33µF*
6V
VIN ISENSE
SHDN
LT1501-5
LBI
SW
OUT
301k
1% LBO GND
1nF
+ 220µF**
10V
TANT
* AVX, TPSC107M006R0150
** AVX, TPSD107M010 R0100
† SUMIDA CD73-220, CD54-220
OR CD43-220. SELECT ACCORDING
TO MAXIMUM LOAD CURRENT
LOW-BATTERY FLAG
(USE EXTERNAL PULL-UP)
LT1500/01 • TA01
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