The LT ®
1959 is a 500kHz monolithic buck mode switching
regulator functionally identical to the LT1506 but optimized
for lower output voltage applications. It will operate down
to 1.21V output compared to 2.42V for the LT1506. A 4.5A
switch is included on the die along with all the necessary
oscillator, control and logic circuitry. High switching frequency allows a considerable reduction in the size of external components. The topology is current mode for fast
transient response and good loop stability.
A special high speed bipolar process and new design techniques achieve high efficiency at high switching frequency.
Efficiency is maintained over a wide output current range
by keeping quiescent supply current to 3.8mA and by utilizing a supply boost capacitor to saturate the power switch.
The LT1959 fits into standard 7-pin DD and fused lead
SO-8 packages. Full cycle-by-cycle short-circuit protection
and thermal shutdown are provided. Standard surface
mount external parts are used, including the inductor and
capacitors. There is the optional function of shutdown or
synchronization. A shutdown signal reduces supply current
to 15μA. Synchronization allows an external logic level signal to increase the internal oscillator from 580kHz to 1MHz.
