LTC3405A
1.5MHz, 300mA
Synchronous Step-Down
Regulator in ThinSOT
U FEATURES DESCRIPTIO ■ The LTC ®3405A is a high efficiency monolithic synchronous buck regulator using a constant frequency, current
mode architecture. Supply current during operation is
only 20µA and drops to 1.5V). In this mode, the efficiency is lower at
light loads, but becomes comparable to Burst Mode
operation when the output load exceeds 25mA. The advantage of pulse skipping mode is lower output ripple and
less interference to audio circuitry.
3405afa 6 LTC3405A U
OPERATIO (Refer to Functional Diagram)
When the converter is in Burst Mode operation, the peak
current of the inductor is set to approximately 100mA regardless of the output load. Each burst event can last from
a few cycles at light loads to almost continuously cycling
with short sleep intervals at moderate loads. In between
these burst events, the power MOSFETs and any unneeded
circuitry are turned off, reducing the quiescent current to
20µA. In this sleep state, the load current is being supplied
solely from the output capacitor. As the output voltage
droops, the EA amplifier’s output rises above the sleep
threshold signaling the BURST comparator to trip and turn
the top MOSFET on. This process repeats at a rate that is …