LTC3786 datasheet(4/38 Pages) LINER

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LTC3784

3784fb

For more information www.linear.com/LTC3784

elecTrical characTerisTics The

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at TA = 25°C, VBIAS = 12V, unless otherwise noted (Note 2).

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 LTC3784 is tested under pulsed load conditions such that

TJ ≈ TA. The LTC3784E 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

LTC3784I is guaranteed over the –40°C to 125°C operating junction

temperature range, the LTC3784H is guaranteed over the –40°C to 150°C

operating temperature range and the LTC3784MP is tested and guaranteed

over the full –55°C to 150°C operating junction temperature range. High

junction temperatures degrade operating lifetimes; operating lifetime

is derated for junction temperatures greater than 125°C. 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 = 43°C/W for the QFN package

and

θJA = 80°C/W for the SSOP package.

Note 3: This IC includes overtemperature protection that is intended to

protect the device during momentary overload conditions. The maximum

rated junction temperature will be exceeded when this protection is active.

Continuous operation above the specified absolute maximum operating

junction temperature may impair device reliability or permanently damage

the device.

Note 4: The LTC3784 is tested in a feedback loop that servos VFB to the

output of the error amplifier while maintaining ITH at the midpoint of the

current limit range.

Note 5: Dynamic supply current is higher due to the gate charge being

delivered at the switching frequency.

Note 6: Rise and fall times are measured using 10% and 90% levels. Delay

times are measured using 50% levels.

Note 7: see Minimum On-Time Considerations in the Applications

Information section.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

INTVCC Linear Regulator

Internal VCC Voltage

6V < VBIAS < 60V, VEXTVCC = 0V

5.2

5.4

5.6

INTVCC Load Regulation

ICC = 0mA to 50mA

0.5

Internal VCC Voltage

6V < VEXTVCC < 13V

5.2

5.4

5.6

INTVCC Load Regulation

ICC = 0mA to 40mA, VEXTVCC = 8.5V

0.5

EXTVCC Switchover Voltage

EXTVCC Ramping Positive

4.5

4.8

EXTVCC Hysteresis

250

Oscillator and Phase-Locked Loop

Programmable Frequency

RFREQ = 25k

RFREQ = 60k

RFREQ = 100k

335

105

400

760

465

kHz

fLOW

Lowest Fixed Frequency

VFREQ = 0V

320

350

380

kHz

Highest Fixed Frequency

VFREQ = INTVCC

488

535

585

kHz

Synchronizable Frequency

PLLIN/MODE = External Clock

850

kHz

PGOOD Output

PGOOD Voltage Low

IPGOOD = 2mA

0.2

0.4

PGOOD Leakage Current

VPGOOD = 5V

±1

µA

PGOOD Trip Level

VFB with Respect to Set Regulated Voltage

VFB Ramping Negative

Hysteresis

–12

–10

2.5

–8

VFB Ramping Positive

Hysteresis

2.5

PGOOD Delay

PGOOD Going High to Low

µs

OV Protection Threshold

VFB Ramping Positive, OVMODE = 0V

1.296

1.32

1.344

BOOST1 and BOOST2 Charge Pump

BOOST Charge Pump Available Output

Current

VSW1,2 = 12V; VBOOST1,2 – VSW1,2 = 4.5V;

FREQ = 0V, Forced Continuous or

Pulse-Skipping Mode

µA

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