LTC3775 查看數據表（PDF） - Linear Technology

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LTC3775

High Frequency Synchronous Step-Down Voltage Mode DC/DC Controller

Linear Technology 

FEATURES

n Wide VIN Range: 4.5V to 38V

n Line Feedforward Compensation

n Low Minimum On-Time: tON(MIN) < 30ns

n Powerful Onboard MOSFET Drivers

n Leading Edge Modulation Voltage Mode Control

n ±0.75%, 0.6V Reference Voltage Accuracy Over

Temperature

n VOUT Range: 0.6V to 0.8VIN

n Programmable, Cycle-by-Cycle Peak Current Limit

n Sense Resistor or RDS(ON) Current Sensing

n Programmable Soft-Start

n Synchronizable Fixed Frequency from 250kHz to 1MHz

n Selectable Pulse-Skipping or Forced Continuous

Modes of Operation

n Low Shutdown Current: 14μA Typical

n Thermally Enhanced 16-Lead MSOP and 3mm × 3mm

QFN Packages

APPLICATIONS

n Automotive Systems

n Telecom and Industrial Power Supplies

n Point of Load Applications

LTC3775

High Frequency

Synchronous Step-Down

Voltage Mode DC/DC

Controller

DESCRIPTION

The LTC®3775 is a high efficiency synchronous step-down

switching DC/DC controller that drives an all N-channel

power MOSFET stage from a 4.5V to 38V input supply

voltage. A patented line feedforward compensation circuit

and a high bandwidth error amplifier provide very fast line

and load transient response.

High step-down ratios are made possible by a low 30ns

minimum on-time, allowing extremely low duty cycles.

MOSFET RDS(ON) current sensing maximizes efficiency.

Alternatively, a sense resistor can be used for higher cur-

rent limit accuracy. Continuous monitoring of the voltages

across the top and bottom MOSFETs allows cycle-by-cycle

control of the inductor current, configurable by external

resistors.

The soft-start function controls the duty cycle during

start-up, providing a smooth output voltage ramp up. The

operating frequency is user programmable from 250kHz

to 1MHz and can be synchronized to an external clock.

L, LT, LTC, LTM, Linear Technology, the Linear logo are registered trademarks, No RSENSE

and UltraFast are trademarks of Linear Technology Corporation. All other trademarks are the

property of their respective owners. Protected by U.S. Patents, including 5408150, 5481178,

5705919, 6580258, 5847554, 5055767.

TYPICAL APPLICATION

VIN

330μF 5V TO 28V

35V

3.16k

57.6k

4.7μF

0.01μF

39.2k

330pF

ILIMT VIN

TG

ILIMB

SENSE

LTC3775

INTVCC BOOST

SW

SS

BG

FREQ

PGND

FB

0.1μF

0.36μH

VOUT

1.2V

470μF 15A

2.5V

×2

3.9nF

10k 10k

4.7k

COMP

SGND

3775 TA01a

Efficiency and Power Loss vs Load Current

100

5

90

VIN = 12V

VOUT = 1.2V

80 CONTINUOUS MODE

4

SW FREQ = 500kHz

70

60

3

EFFICIENCY

50

40

2

30

20

1

POWER LOSS

10

0

0.01

0.1

1

10

LOAD CURRENT (A)

0

100

3775 TA01b

3775fa

1

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