LTC3548 datasheet(6/16 Pages) LINER

6 / 16 page

LTC3548

3548fc

BLOCK DIAGRAM

The LTC3548 uses a constant-frequency, current mode

architecture. The operating frequency is set at 2.25MHz

and can be synchronized to an external oscillator. Both

channels share the same clock and run in-phase. To suit a

variety of applications, the selectable Mode pin allows the

user to choose between low noise and high efﬁciency.

The output voltage is set by an external divider returned

to the VFB pins. An error ampliﬁer compares the divided

output voltage with a reference voltage of 0.6V and adjusts

the peak inductor current accordingly. An undervoltage

comparator will pull the POR output low if the output

voltage is not above –8.5% of the reference voltage. The

POR output will go high after 262,144 clock cycles (about

117ms) of achieving regulation.

–

UVDET

OVDET

0.6V

0.65V

0.55V

–

0.35V

ITH

SWITCHING

LOGIC

AND

BLANKING

CIRCUIT

LATCH

BURST

ICOMP

IRCMP

ANTI

SHOOT-

THRU

BURST

CLAMP

SLOPE

COMP

SLEEP

POR

COUNTER

0.6V REF

OSC

REGULATOR 2 (IDENTICAL TO REGULATOR 1)

PGOOD1

PGOOD2

SHUTDOWN

VIN

REGULATOR 1

SW1

GND

POR

GND

SW2

5Ω

MODE/SYNC

VFB1

RUN1

RUN2

VFB2

3548 BD

Main Control Loop

During normal operation, the top power switch (P-channel

MOSFET) is turned on at the beginning of a clock cycle

when the VFB voltage is below the the reference voltage.

The current into the inductor and the load increases until

the current limit is reached. The switch turns off and

energy stored in the inductor ﬂows through the bottom

switch (N-channel MOSFET) into the load until the next

clock cycle.

The peak inductor current is controlled by the internally

compensated ITH voltage, which is the output of the

error ampliﬁer.This ampliﬁer compares the VFB pin to

the 0.6V reference. When the load current increases,

the VFB voltage decreases slightly below the reference.

OPERATION

LTC3548 Datasheet(PDF) 6 Page - Linear Technology

LTC3548 Datasheet(HTML) 6 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL