LTC3541_15 Datasheet, PDF(8/20 Page) Linear Technology – High Efficiency Buck VLDO Regulator

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LTC3541_15 Datasheet, PDF (8/20 Pages) Linear Technology – High Efficiency Buck VLDO Regulator

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LTC3541

FU CTIO AL BLOCK DIAGRA

VIN(MIN) â¥ LVOUT + 1.4V

VIN

2.2ÂµH

IOUT(BUCK) = 500mA

10ÂµF

500mA BUCK

VIN

REF

GND

PGND

ENBUCK

ENVLDO

MODE

CONTROL

LOGIC

VLDO/LINEAR REG

REF

REF +

LFB â

CNTRL

GND

PGND

22pF

BUCKFB

LVIN

VIN

LVIN

LVOUT(MAX) < VIN â 1.4V

IOUT = 300mA (VLDO REG)

IOUT = 30mA (LINEAR REG)

LVOUT

2.2ÂµF

LFB

3541 F01

Figure 1. LTC3541 Functional Block Diagram

OPERATIO

The LTC3541 contains a high efficiency synchronous

buck converter, a very low dropout regulator (VLDO) and

a linear regulator. It can be used to provide up to two

output voltages from a single input voltage making the

LTC3541 ideal for applications with limited board space.

The combination and configuration of these major blocks

within the LTC3541 is determined by way of the control

pins ENBUCK and ENVLDO as defined in Table 1.

With the ENBUCK pin driven to a logic high and ENVLDO

driven to a logic low, the LTC3541 enables the buck con-

verter to efficiently reduce the voltage provided at the VIN

input pin to an output voltage which is set by an external

feedback resistor network. The buck regulator can be con-

figured for Pulse-Skip or Burst Mode operation by driving

the MODE pin to a logic high or logic low respectively. The

buck regulator is capable of providing a maximum output

current of 500mA, which must be taken into consideration

when using the buck regulator to provide the power for

both the VLDO and for external loads.

With the ENBUCK pin driven to a logic low and ENVLDO

driven to a logic high, the LTC3541 enables the linear

regulator, providing a low noise regulated output voltage

at the LVOUT pin while drawing minimal quiescent current

from the VIN input pin. This feature allows output voltage

LVOUT to be brought into regulation without the presence

of the LVIN voltage.

With the ENBUCK and ENVLDO pins both driven to a

logic high, the LTC3541 enables the high efficiency buck

converter and VLDO regulator, providing dual output opera-

tion from a single input voltage. When configured in this

manner, the LTC3541âs auto start-up sequencing feature

will bring the buck output into regulation in a controlled

manner prior to enabling the VLDO regulator without the

3541fa

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