LTC4366 datasheet(5/32 Pages) AD

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LTC7862

Rev 0

For more information www.analog.com

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Fault Timer and WARNB Output

ISWITCHING

TMR Pull-Up Current (Switching)

TMR = 0V, VFB = 0.83V

–35

–40

–45

µA

IDROPOUT

TMR Pull-Down Current (Dropout)

TMR = 1V, VFB = 0.77V

0.7

1.1

1.4

µA

ICOOLDOWN

TMR Pull-Down Current (Cool-Down)

TMR = 2.5V

0.7

1.1

1.4

µA

TMR Switching Off Threshold

2.13

2.19

2.23

TMR Retry Threshold

0.19

0.25

0.31

TMR Switching Set Time

(Initial Fault Period) per 1µF

ms/µF

TMR Switching Set Time

(Retry Period) per 1µF

ms/µF

TMR Cool-Down Time per 1µF

1700

ms/µF

DRETRY

Retry Duty Cycle During a Sustained Fault

1.8

2.7

3.5

VWARNB

WARNB Voltage Low

IWARNB = 2mA

0.02

0.04

IWARNB

WARNB Leakage Current

VWARNB = 3.3V

µA

tWARNB

Delay from TG Going High to WARNB

Going High Impedance

µs

ELECTRICAL CHARACTERISTICS The

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at TA = 25°C (Note 2), VIN = 12V, VRUN = 5V, VEXTVCC = 0V, VDRVUV = 0V

unless otherwise noted.

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

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

Maximum Ratings for extended periods may affect device reliability and

lifetime.

Note 2: The LTC7862 is tested under pulsed load conditions such that TJ ≈

TA. The LTC7862E is guaranteed to meet performance specifications 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 LTC7862I is guaranteed over the

–40°C to 125°C operating junction temperature range and the LTC7862H

is guaranteed over the –40°C to 150°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. High temperatures degrade operating

lifetimes; operating lifetime is derated for junction temperatures greater

than 125ºC. 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 = 38°C/W for the TSSOP package and θJA = 43°C/W for the

QFN 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 LTC7862 is tested in a feedback loop that servos VITH to a

specified voltage and measures the resultant VFB. The specification at

85°C is not tested in production and is assured by design, characterization

and correlation to production testing at other temperatures (125°C for the

LTC7862E and LTC7862I, 150°C for the LTC7862H). For the LTC7862I

and LTC7862H, the specification at 0°C is not tested in production and is

assured by design, characterization and correlation to production testing

at –40°C.

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

delivered at the switching frequency. See the Applications Information

section.

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

Delay times are measured using 50% levels.

Note 7: The minimum on-time condition is specified for an inductor

peak-to-peak ripple current >40% of IMAX (See Minimum On-Time

Considerations in the Applications Information section).

Note 8: Do not apply a voltage or current source to these pins. They must

be connected to capacitive loads only, otherwise permanent damage may

occur.

Note 9: The minimum input supply operating range is dependent on the

DRVCC UVLO thresholds as determined by the DRVUV pin setting.

Note 10: All voltages with respect to GND unless otherwise noted. Positive

currents are into pins; negative currents are out of pins unless otherwise

noted.

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