LTC3621 datasheet(3/20 Pages) AD

3 / 20 page

LTC3644/LTC3644-2

Rev. 0

For more information www.analog.com

ELECTRICAL CHARACTERISTICS

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 LTC3644/LTC3644-2 is tested under pulsed load conditions

such that TJ ≈ TA. The LTC3644E is guaranteed to meet specified

performance from 0°C to 85°C. Specifications over the –40°C to

125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LTC3644I 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

The l denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at TA = 25°C (Note 2). SVIN = VIN1 = VIN2 = VIN3 = VIN4 = 12V, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

NMOS Switch Leakage

PMOS Switch Leakage

0.1

µA

RDS(ON)

NMOS On Resistance

PMOS On Resistance

300

mΩ

tON(MIN)

Minimum On Time

(Note 6)

VRUN

RUN Input High

RUN Input Low

0.35

1.0

RUN Input Current

VRUN = 12V

0.1

VMODE/SYNC

Pulse-Skipping Mode

Forced Continuous Mode

Burst Mode Operation

1.0

VINTVCC – 0.4

0.3

VINTVCC – 1.2

VINTVCC + 0.3V

MODE/SYNC Input Current

0.1

100

PHASE Input Threshold

Input Low

Input High

VINTVCC – 0.4

0.4

PHASE Input Current

VPHASE = 6V

0.1

100

tSS

Internal Soft Start Time

1.1

ILIM

Peak Current Limit

1.25A Regulator

2.5A Regulator (2-Channel Combined)

3.75A Regulator (3-Channel Combined)

1.8

2.2

4.4

6.6

2.6

VINTVCC Undervoltage Lockout

SVIN Ramping Up

2.35

2.5

2.65

VINTVCC Undervoltage Lockout Hysteresis

250

VIN Overvoltage Lockout Rising

VIN Overvoltage Lockout Hysteresis

400

fOSC

Oscillator Frequency

LTC3644-2

LTC3644

1.8

0.82

2.25

1.00

2.60

1.16

MHz

SYNC Capture Range

% of Programmed Frequency

150

VINTVCC

VINTVCC Voltage

SVIN > 5.5V

Power Good Range

±7.5

RPGOOD

Power Good Resistance

275

350

tPGOOD

PGOOD Delay

PGOOD Low to High

PGOOD High to Low

Cycles

Phase Shift Between Channel 1/2 and

Channel 3/4

VPHASE = 0V

VPHASE = INTVCC, VMODE/SYNC = 0V

180

Deg

(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: The quiescent current in active mode does not include switching

loss of the power FETs.

Note 4: The LTC3644 is tested in a proprietary test mode that connects

VFB to the output of error amplifier.

Note 5: This IC includes overtemperature protection that is intended to protect the

device during momentary overload conditions. Junction temperature will exceed

125°C when overtemperature protection is active. Continuous operation above the

specified maximum operating junction temperature may impair device reliability.

Note 6: The minimum on-time is determined by the speed of the top

switch driver and peak current comparator. The typical value listed here is

guaranteed by design.

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