LM3551 datasheet(4/23 Pages) TI1

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LM3551, LM3552

SNVS371C – AUGUST 2005 – REVISED MARCH 2011

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Electrical Characteristics

(1) (2)

Limits in standard typeface are for TJ = +25° C. Limits in boldface type apply over the full operating junction temperature

range (-40°C

≤ TJ ≤ +110°C). Unless otherwise noted, specifications apply to the LM3551 and LM3552 Typical Application

Circuit (pg. 1) with: VIN = 3.6V, V(SD) = 0V for LM3551 and V(EN) = VIN for LM3552, ILOAD = 0A

(3)

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Quiescent Current

FB = VIN (Not Switching)

1.47

2.0

V(SD) = VIN, LM3551

2.55

5.0

ISD

Shutdown Current

µA

V(EN) = 0V, LM3552

0.1

2.3

ICL

(4)

Switch Current Limit

VIN = 3.0V

(5)

2.1

VFB

Feedback Voltage

1.2285

1.265

1.2915

IFB

(6)

Feedback Pin Bias Current

Error Amp Transconductance

ΔI = 5µA

135

µmho

Error Amp Voltage Gain

135

V/V

DMAX

Maximum Duty Cycle

92.5

fsw

Switching Frequency

0.9

1.25

1.6

MHz

Shutdown Pin Current

ISDPIN

VSD = 0V

3.0

µA

(LM3551)

Enable Pin Current

IENPIN

VEN = 3.6V

3.0

µA

(LM3552)

VT/F = 0V

IT/FPIN

T/F Pin Current

VT/F = VIN

IL-SW

SW Pin Leakage Current

VL-SW = 20V

0.07

µA

RDSON-SW

SW Pin RDSON

ISW = 0.5A

0.165

Ω

IL-T

FET-T Leakage Current

0.1

µA

RDSON-T

FET-T RDSON

0.98

Ω

IL-F

FET-F Leakage Current

0.1

µA

RDSON-F

FET-F RDSON

0.36

Ω

Output High

1.2

Shutdown/Enable Pin

ThSD/EN

Threshold

Output Low

0.3

Output High

1.2

ThT/F

T/F Pin Threshold

Output Low

0.3

On Threshold

2.25

2.48

2.70

Under Voltage Protection

UVP

Thresholds

Off Threshold

2.43

2.58

2.77

On Threshold

11.3

12.4

Over Voltage Protection

OVP

Thresholds

Off Threshold

9.2

10.6

VFTO

Flash Timeout trip-point

0.99

1.16

1.32

IFTO

Flash Timeout Current

1.12

1.4

1.68

µA

VSS

Soft-Start Voltage

1.18

1.25

1.32

ISS

Soft-Start Current

11.5

µA

(1)

All voltages are with respect to the potential at the GND pin.

(2)

Min and Max limits are guaranteed by design, test, or statistical analysis. Typical (Typ) numbers are not guaranteed, but do represent

the most likely norm. Unless otherwise specified, conditions for Typ specifications are: VIN = 3.6V and TA = 25ºC.

(3)

CIN and COUT,: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics

(4)

Duty cycle affects current limit due to ramp generator.

(5)

Current limit at 0% duty cycle. See TYPICAL PERFORMANCE section for Switch Current Limit vs. VIN

(6)

Bias current flows into FB pin.

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