Data Sheet

LT8638-2

analog.com

Rev.0

29 of 35

The LT8638-2’s internal power switches are capable of safely delivering up to 12A of peak output current. However,

due to thermal limits, the package can only handle 12A loads for short periods of time. This time is determined by

how quickly the case temperature approaches the maximum junction rating. Figure 52 shows an example of how

case temperature rise changes with the duty cycle of a 1kHz pulsed 12A load.

Figure 52. Case Temperature Rise vs. 12A Pulsed Load

The LT8638-2 device’s top switch current limit decreases with higher duty cycle operation for slope compensation.

This also limits the peak output current the LT8638-2 can deliver for a given application. See the curve in Typical

Performance Characteristics.

TYPICAL APPLICATIONS

Figure 53. 400kHz 5V 10A Step-Down Converter with Soft-Start and Power Good

DC2929A DEMO BOARD

VIN = 12V

VOUT = 3.3V

fSW = 2MHz

STANDBY LOAD = 0.25A

1kHz PULSED LOAD = 12A

DUTY CYCLE OF 12A LOAD

0

0.2

0.4

0.6

0.8

1.0

0

10

20

30

40

50

60

70

80

90

100

LT8638-2

SW

BIAS

FB

VIN

5.4V TO 42V

GND

RT

VIN

GND

VIN

GND

VOUT

5V

10A

47µF

×3

1210

X5R/X7R

33pF

4.7µF

1µF

0603

BST

1μF

105kΩ

100kΩ

13.7kΩ

3.3µH

0.1µF

fSW = 400kHz

L: XAL1010

SS

10nF

PG

SYNC/MODE

CLKOUT

INTVCC

100kΩ

PHMODE

VC

1µF

0603

820pF

9.31kΩ

EN/UV