LTC7803 datasheet(6/44 Pages) AD

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LTC7817

Rev 0

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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 LTC7817 is tested under pulsed load conditions such

that TJ ≈ TA. The LTC7817E 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

LTC7817I is guaranteed over the –40°C to 125°C operating junction

temperature range, the LTC7817J is guaranteed over the –40°C to 150°C

operating junction temperature range, and the LTC7817H is guaranteed

over the –40°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 (in °C/W) is the package

thermal impedance.

Note 3: When SENSE1– ≥ 3.2V or EXTVCC ≥ 4.8V, VBIAS supply current is

transferred to these pins to reduce the total input supply quiescent current.

SENSE1– bias current is reflected to the buck channel 1 input supply (VIN1)

by the formula IVIN1 = ISENSE1– • VOUT1/(VIN1 • η), where η is the efficiency.

EXTVCC bias current is similarly reflected to a buck channel input supply

when biased by a buck channel output. To minimize input supply current,

select channel 1 to be the lowest output voltage greater than 3.2V and

connect EXTVCC to the lowest output voltage greater than 4.8V.

Note 4: The LTC7817 is tested in a feedback loop that servos VITH1,2,3

to a specified voltage and measures the resultant VFB1,2,3. The

specifications at 0°C and 85°C are not tested in production and are

assured by design, characterization and correlation to production testing

at other temperatures (125°C for the LTC7817E/LTC7817I, 150°C for the

LTC7817J/LTC7817H)

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

delivered at the switching frequency. See Applications Information.

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 IL(MAX) (See Minimum On-Time

Considerations in the Applications Information section).

Note 8: 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 9: Do not apply a voltage or current source to these pins. They must

be connected to capacitive loads only, otherwise permanent damage may

occur.

ELECTRICAL CHARACTERISTICS

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