LTC3541EDD-3 Просмотр технического описания (PDF) - Linear Technology

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LTC3541EDD-3

High Efficiency Buck + VLDO Regulator

Linear Technology 

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OPERATIO

Transitioning from linear regulator mode to VLDO mode,

accomplished by bringing ENBUCK from a logic low to a

logic high while ENVLDO is a logic high or as occurs during

the auto start-up sequence, is designed to be as seam-

less and transient free as possible. The precise transient

response of LVOUT due to this transition is a function of

COUT and the load current. Waveforms given in the Typical

Performance Characteristics section show typical transient

responses using the minimum COUT of 2.2µF and load

currents of 1mA and 30mA respectively. Generally, the

amplitude of any transients present will decrease as COUT

is increased. To ensure reliable operation and adherence

to the load regulation limits presented in the Electrical

Characterstics table, the load current must not exceed

the linear regulator IOUT limit of 30mA within 20ms after

ENBUCK has transitioned to a logic high. The 300mA IOUT

limit of VLDO applies thereafter. Further, for configurations

that do not use the LTC3541-3’s buck regulator to provide

the VLDO input voltage (LVIN), the user must ensure a

stable LVIN voltage is present no less than 1ms prior to

ENBUCK transitioning to a logic high.

LTC3541-3

In a similar manner, transitioning from VLDO mode to

linear regulator mode, accomplished by bringing ENBUCK

from a high low to a logic low while ENVLDO is a logic

high, is designed to be as seamless and transient free as

possible. Again, the precise transient response of LVOUT

due to this transition is a function of COUT and the load

current. Waveforms given in the Typical Performance

Characteristics section show typical transient responses

using the minimum COUT of 2.2µF and load currents of

1mA and 30mA respectively. Generally, the amplitude of

any transients present will decrease as COUT is increased.

To ensure reliable operation and adherence to the load

regulation limits presented in the Electrical Characterstics

table, the load current must not exceed the linear regulator

IOUT limit of 30mA 1ms prior to ENBUCK transitioning to

a logic low and thereafer. Further, for configurations that

do not use the LTC3541-3’s buck regulator to provide the

VLDO input voltage (LVIN), the user must continue to ensure

a stable LVIN voltage no less than 1ms after ENBUCK has

transitioned to a logic low.

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