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LTC3121

3121fa

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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: Voltage transients on the SW pin beyond the DC limit specified in

the Absolute Maximum Ratings are non-disruptive to normal operations

when using good layout practices, as shown on the demo board or

described in the data sheet or application notes.

Note 3: The LTC3121 is tested under pulsed load conditions such that

TA ≈ TJ. The LTC3121E 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 LTC3121I is guaranteed

to meet specifications over the full –40°C to 125°C operating junction

The l denotes the specifications which apply over the full operating junction

temperature range, otherwise specifications are at TA = 25°C (Note 3). VIN = 3.6V, VOUT = 12V, RT = 57.6k unless otherwise noted.

PARAMETER

CONDITIONS

MIN.

TYP

MAX

UNITS

Minimum Start-Up Voltage

VOUT = 0V

1.7

1.8

Input Voltage Range

After VOUT ≥ 2.2V

0.5

5.5

Output Voltage Adjust Range

2.2

Feedback Voltage

1.178

1.202

1.225

Feedback Input Current

VFB = 1.4V

Quiescent Current, Shutdown

VSD = 0V, VOUT = 0V, Not Including Switch Leakage

0.01

µA

Quiescent Current, Active

VC = 0V, Measured On VIN, Non-Switching

500

700

µA

Quiescent Current, Burst

Measured on VIN, VFB > 1.4V

Measured on VOUT, VFB > 1.4V

µA

N-channel MOSFET Switch Leakage Current

VSW = 15V, VOUT = 15V, VC = 0V (Note 6)

0.1

µA

P-channel MOSFET Switch Leakage Current

VSW = VIN = 0V, VOUT = 15V (Note 6)

0.1

µA

N-channel MOSFET Switch On-Resistance

0.121

P-channel MOSFET Switch On-Resistance

0.188

N-channel MOSFET Current Limit

VIN = 3.3V

1.5

1.8

2.7

Maximum Duty Cycle

VFB = 1.0V

Minimum Duty Cycle

VFB = 1.4V

Switching Frequency

0.85

1.15

MHz

SYNC Frequency Range

0.1

MHz

PWM/SYNC Input High

0.9 •VCC

PWM/SYNC Input Low

0.1•VCC

PWM/SYNC Input Current

VPWM/SYNC = 5.5V

0.01

µA

CAP Clamp Voltage

VOUT > 6.1V, Referenced to VOUT

–5.2

–5.6

–6.0

Error Amplifier Transconductance

100

130

µS

Error Amplifier Output Current

±25

µA

Soft-Start Time

SD Input High

1.6

SD Input Low

0.25

SD Input Current

VSD = 5.5V

µA

temperature range. 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 is the thermal

impedance of the package.

Note 4: The LTC3121 includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed 125°C when overtemperature shutdown is active.

Continuous operation above the specified maximum operating junction

temperature may result in device degradation or failure.

Note 5: Failure to solder the exposed backside of the package to the PC

board ground plane will result in a thermal impedance much higher than

the rated package specifications.

Note 6: Measured using a propietary test mode to ensure anti-ringing

switch between VIN ans SW is not active.

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