Datasheet

LTM4624
8
4624fb
For more information www.linear.com/LTM4624
OPERATION
The LTM4624 is a standalone nonisolated switch mode
DC/DC power supply. It can deliver up to 4A DC (5A
peak) output current with few external input and output
capacitors. This module provides precisely regulated
output voltage adjustable between 0.6V to 5.5V via one
external resistor over a 4V to 14V input voltage range.
With an external bias supply, this module operates with
an input voltage down to 2.375V. The typical application
schematic is shown in Figure 20.
The LTM4624 contains an integrated constant on-time
valley current mode regulator, power MOSFETs, inductor,
and other supporting discrete components. The default
switching frequency is 1MHz. For noise-sensitive applica
-
tions, the switching frequency can be adjusted by external
resistors. See the Applications Information section.
With current mode control and internal feedback loop
compensation, the LTM4624 module has sufficient stabil
-
ity margins and good transient per
formance with a wide
range of
output capacitors, even with all ceramic output
capacitors.
Current mode control provides cycle-by-cycle fast cur-
rent limiting. Foldback current limiting is provided in an
over
current condition indicated by a drop in V
FB
reducing
inductor valley current to approximately 40% of the origi-
nal value. Internal output overvoltage and undervoltage
comparators pull the open-drain PGOOD output low if the
output
feedback
voltage exits a ±10% window around the
regulation point. Continuous operation is forced during
OV and UV conditions except during start-up when the
TRACK pin is ramping up to 0.6V
Pulling the RUN pin below 1.1V forces the controller into
its shutdown state, turning off both power MOSFETs
and most of the internal control circuitry. At light load
currents, discontinuous mode (DCM) operation can be
enabled to achieve higher efficiency compared to continu
-
ous mode (CCM) by pulling the MODE pin to SGND. The
TRACK/SS pin is used for power supply tracking and
soft-start programming. See the Applications Informa-
tion section.