LTC3541-1 Datasheet, PDF(8/20 Page) Linear Technology – High Efficiency Buck + VLDO Regulator

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LTC3541-1 Datasheet, PDF (8/20 Pages) Linear Technology – High Efficiency Buck + VLDO Regulator

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LTC3541-1

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

35411 F01

Figure 1. LTC3541-1 Functional Block Diagram

OPERATIO

The LTC3541-1 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

LTC3541-1 ideal for applications with limited board space.

The combination and configuration of these major blocks

within the LTC3541-1 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 LTC3541-1 enables the buck

converter 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 configured for Pulse-Skip or Burst Mode opera-

tion 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 LTC3541-1 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 LTC3541-1 enables the high efficiency

buck converter and VLDO regulator, providing dual output

operation from a single input voltage. When configured

in this manner, the LTC3541-1âs auto start-up sequencing

feature will bring the VLDO/linear regulator output into

regulation in a controlled manner prior to enabling the

35411fa

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