5

LM3478

www.ti.com

SNVS085X – JULY 2000 – REVISED DECEMBER 2017

Product Folder Links: LM3478

Submit Documentation Feedback

Copyright © 2000–2017, Texas Instruments Incorporated

(1)

For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

6.4 Thermal Information

THERMAL METRIC(1)

LM3478

UNIT

D

DGK

8 PINS

8 PINS

RθJA

Junction-to-ambient thermal resistance

105.3

157.2

°C/W

RθJC(top)

Junction-to-case (top) thermal resistance

50.3

49.9

°C/W

RθJB

Junction-to-board thermal resistance

55.8

77.1

°C/W

ψJT

Junction-to-top characterization parameter

6.8

4.7

°C/W

ψJB

Junction-to-board characterization parameter

54.7

75.8

°C/W

RθJC(bot)

Junction-to-case (bottom) thermal resistance

N/A

N/A

°C/W

(1)

The voltage on the drive pin, VDR is equal to the input voltage when input voltage is less than 7.2 V. VDR is equal to 7.2 V when the

input voltage is greater than or equal to 7.2 V.

(2)

The limits for the maximum duty cycle can not be specified since the part does not permit less than 100% maximum duty cycle

operation.

(3)

For this test, the FA/SD pin is pulled to ground using a 40-K resistor.

(4)

For this test, the FA/SD pin is pulled to 5 V using a 40-K resistor.

6.5 Electrical Characteristics

Unless otherwise specified, VIN = 12V, RFA = 40kΩ, TJ = 25°C

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

VFB

Feedback Voltage

VCOMP = 1.4V, 2.97 ≤ VIN ≤ 40V

1.2416

1.26

1.2843

V

VCOMP = 1.4V, 2.97 ≤ VIN ≤ 40V, −40°C

≤ TJ ≤ 125°C

1.228

1.292

ΔVLINE

Feedback Voltage Line

Regulation

2.97

≤ VIN ≤ 40V

0.001

%/V

ΔVLOAD

Output Voltage Load

Regulation

IEAO Source/Sink

±0.5

%/A

VUVLO

Input Undervoltage

Lock-out

2.85

V

−40°C ≤ TJ ≤ 125°C

2.97

VUV(HYS)

Input Undervoltage

Lock-out Hysteresis

170

mV

−40°C ≤ TJ ≤ 125°C

130

210

Fnom

Nominal Switching

Frequency

RFA = 40KΩ

400

kHz

RFA = 40KΩ, −40°C ≤ TJ ≤ 125°C

350

440

RDS1 (ON)

Driver Switch On

Resistance (top)

IDR = 0.2A, VIN= 5V

16

Ω

RDS2 (ON)

Driver Switch On

Resistance (bottom)

IDR = 0.2A

4.5

VDR (max)

Maximum Drive Voltage

Swing(1)

VIN < 7.2V

VIN

V

VIN ≥ 7.2V

7.2

Dmax

Maximum Duty Cycle(2)

100%

Tmin (on)

Minimum On Time

325

ns

−40°C ≤ TJ ≤ 125°C

210

600

ISUPPLY

Supply Current (non-

switching)

See (3)

2.7

mA

See (3),

−40°C ≤ TJ ≤ 125°C

3.3

IQ

Quiescent Current in

Shutdown Mode

VFA/SD = 5V

(4), V

IN = 5V

5

µA

VFA/SD = 5V

(4), V

IN = 5V, −40°C ≤ TJ ≤

125°C

10

VSENSE

Current Sense

Threshold Voltage

VIN = 5V

135

156

180

mV

VIN = 5V, −40°C ≤ TJ ≤ 125°C

125

190

VSC

Short-Circuit Current

Limit Sense Voltage

VIN = 5V

343

mV

VIN = 5V, −40°C ≤ TJ ≤ 125°C

250

415