LTC3775EUD 查看數據表（PDF） - Linear Technology

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LTC3775EUD

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

Linear Technology 

LTC3775

ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating

junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 12V, VRUN = 5V, unless otherwise specified.

SYMBOL

PARAMETER

CONDITIONS

MIN TYP MAX UNITS

Oscillator

fOSC

fHIGH

fLOW

fSYNC

tON(MIN)

tOFF(MIN)

DCMAX

VMODE

VMODE(HYST)

RMODE/SYNC

Driver

Oscillator Frequency

Maximum Oscillator Frequency

Minimum Oscillator Frequency

External Sync Frequency Range

TG Minimum On-Time

TG Minimum Off-Time

Maximum TG Duty Cycle

MODE/SYNC Threshold

MODE/SYNC Hysteresis

MODE/SYNC Input Resistance to SGND

RSET = 39.2k

l 425

500

575

kHz

l 1000

kHz

l

250

kHz

With Reference to Free Running

–20

20

%

(Notes 6, 8) VMODE/SYNC = 0V

(Note 6)

30

ns

300

ns

fOSC = 500kHz

l 90

%

MODE/SYNC Rising

1.2

V

430

mV

50

kΩ

BG RUP

TG RUP

BG RDOWN

TG RDOWN

BG, TG t2D

Bottom Gate (BG) Pull-Up On-Resistance

Top Gate (TG) Pull-Up On-Resistance

Bottom Gate (BG) Pull-Down On-Resistance

Top Gate (TG) Pull-Down On-Resistance

Bottom Gate Off to Top Gate On Delay

Top Switch-On Delay Time

CL = 3300pF (Note 7)

2.5

Ω

2.5

Ω

1.0

Ω

1.5

Ω

15

ns

TG, BG t1D

Top Gate Off to Bottom Gate On Delay

Synchronous Switch-On Delay Time

CL = 3300pF (Note 7)

15

ns

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The LTC3775 is tested under pulsed load conditions such that TJ ≈ TA.

The LTC3775E is guaranteed to meet specifications from 0°C to 85°C

junction temperature. Specifications over the –40°C to 125°C operating

junction temperature range are assured by design, characterization and

correlation with statistical process controls. The LTC3775I is guaranteed

over the –40°C to 125°C operating junction temperature range. Note that

the maximum ambient temperature consistent with these specifications

is determined by specific operating conditions in conjunction with board

layout, the rated package thermal impedance and other environmental

factors.

The junction temperature (TJ, in °C) is calculated from the ambient

temperature (TA, in °C) and power dissipation (PD, in Watts) according to

the formula:

TJ = TA + (PD • θJA), where θJA (in °C/W) is the package thermal

impedance.

Note 3: Failure to solder the exposed pad of the UD package to the PC

board will result in a thermal resistance much higher than 68°C/W.

Note 4: All currents into device pins are positive; all currents out of device

pins are negative. All voltages are referenced to ground unless otherwise

specified.

Note 5: Supply current in normal operation is dominated by the current

needed to charge and discharge the external MOSFET gates. This current

will vary with supply voltage and the external MOSFETs used.

Note 6: Guaranteed by design, not subject to test.

Note 7: Rise and fall times are measured using 10% and 90% levels. Delay

and nonoverlap times are measured using 50% levels.

Note 8: The LTC3775 leading edge modulation architecture does not have

a minimum TG pulse width requirement. The TG minimum pulse width is

limited by the SW node rise and fall times.

3775fa

4

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