The LT?1121/LT1121-3.3/LT1121-5 are micropower low
dropout regulators with shutdown. These devices are capable
of supplying 150mA of output current with a dropout
voltage of 0.4V. Designed for use in battery-powered systems,
the low quiescent current, 30μA operating and 16μA
in shutdown, makes them an ideal choice. The quiescent
current is well-controlled; it does not rise in dropout as it
does with many other low dropout PNP regulators.
Other features of the LT1121/LT1121-3.3/LT1121-5 include
the ability to operate with very small output capacitors. They
are stable with only 0.33μF on the output while most older
devices require between 1μF and 100μF for stability. Small
ceramic capacitors can be used, enhancing manufacturability.
Also the input may be connected to ground or a
reverse voltage without reverse current fl ow from output
to input. This makes the LT1121 series ideal for backup
power situations where the output is held high and the
input is at ground or reversed. Under these conditions only
16μA will fl ow from the output pin to ground.