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LTC7812

7812fc

For more information www.linear.com/LTC7812

ELECTRICAL CHARACTERISTICS The

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at TA = 25°C. VBIAS = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless otherwise

noted. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

High Fixed Frequency

VFREQ = INTVCC; PLLIN/MODE = DC Voltage

485

535

585

kHz

Synchronizable Frequency

PLLIN/MODE = External Clock

850

kHz

PGOOD1 Output

PGOOD1 Voltage Low

IPGOOD1 = 2mA

0.2

0.4

PGOOD1 Leakage Current

VPGOOD1 = 5V

±1

µA

PGOOD1 Trip Level

VFB1 with Respect to Set Regulated Voltage

VFB1 Ramping Negative

–13

–10

–7

Hysteresis

2.5

VFB1 Ramping Positive

Hysteresis

2.5

Delay For Reporting a Fault

µs

OV2 Boost Overvoltage Indicator Output

OV2 Voltage Low

IOV2 = 2mA

0.2

0.4

OV2 Leakage Current

VOV2 = 5V

±1

µA

OV2 Trip Level

VFB2 Ramping Positive with Respect to Set

Regulated Voltage

Hysteresis

1.5

BOOST2 Charge Pump

BOOST2 Charge Pump Available Output

Current

VBOOST2 = 16V; VSW2 = 12V;

Forced Continuous Mode

µA

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 LTC7812 is tested under pulsed load conditions such that

TJ ≈ TA. The LTC7812E 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 LTC7812I is guaranteed

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

LTC7812H 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. TJ is calculated from the ambient temperature

TA and power dissipation PD according to the following formula: TJ = TA +

(PD • qJA), where qJA = 44°C/W.

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 LTC7812 is tested in a feedback loop that servos VITH1,2 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 LTC7812E/LTC7812I, 150°C for the LTC7812H). For the LTC7812I

and LTC7812H, 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 the 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.

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