LTC3416 데이터 시트보기 (PDF) - Linear Technology

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LTC3416

4A, 4MHz, Monolithic Synchronous Step-Down Regulator with Tracking

Linear Technology 

LTC3416

W

FU CTIO AL DIAGRA

EXPOSED

SVIN SGND PAD

ITH

16

5

21

18

TRACK

3

VOLTAGE

REFERENCE

+

SLOPE

COMPENSATION

RECOVERY

PMOS CURRENT

COMPARATOR

PVIN

7 14

–

ERROR

VFB

AMPLIFIER

19

0.74V +

–

+

0.86V –

RUN/SS

4 RUN

PGOOD

17

OSCILLATOR

SLOPE

COMPENSATION

LOGIC

NMOS CURRENT

COMPARATOR

8

9

SW

12

13

1

10

PGND

11

2

20

RT

3416 FD

U

OPERATIO

Main Control Loop

The LTC3416 is a monolithic, constant frequency, current

mode step-down DC/DC converter. During normal opera-

tion, the internal top power switch (P-channel MOSFET) is

turned on at the beginning of each clock cycle. Current in

the inductor increases until the current comparator trips

and turns off the top power MOSFET. The peak inductor

current at which the current comparator shuts off the top

power switch is controlled by the voltage on the ITH pin.

The error amplifier adjusts the voltage on the ITH pin by

comparing the feedback signal from a resistor divider on

the VFB pin with an internal 0.8V reference. When the load

current increases, it causes a reduction in the feedback

voltage relative to the reference. The error amplifier raises

6

the ITH voltage until the average inductor current matches

the new load current. When the top power MOSFET shuts

off, the synchronous power switch (N-channel MOSFET)

turns on until either the bottom current limit is reached or

the beginning of the next clock cycle. The bottom current

limit is set at –5A.

The operating frequency is externally set by an external

resistor connected between the RT pin and ground. The

practical switching frequency can range from 300kHz to

4MHz.

Overvoltage and undervoltage comparators will pull the

PGOOD output low if the output voltage comes out of

regulation by ±7.5%. In an overvoltage condition, the top

3416f

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