Data Sheet

LT4423

analog.com

Rev. 0

11 of 18

High-Voltage Load Switch with Load Sharing and Undervoltage Lockout

Figure 15 demonstrates a high-voltage load switch and load-sharing application with a precision undervoltage

lockout using an LTC2965 voltage supervisor. Two LT4423s are connected in parallel to the load. The power paths

are enabled only when the 24V input supply is above 20V. If the 24V source is removed, the load is disconnected from

the input.

Figure 15. High-Voltage Load Switch and Load Sharing with UVLO

Layout and Thermal Considerations

The following advice should be considered when laying out a printed circuit board for the LT4423. First, connect the

exposed pad (also connected to IN) to a sufficiently large copper plane for thermal relief. Use Figure 16 to find the

minimum copper area (connected to IN) required to limit junction temperature for a given load current and ambient

temperature.

Figure 16. Minimum Thermal Copper vs Load Current and Ambient Temperature

VIN = 24V

C1

10µF

REF

INH

INL

GND

OUT

VIN

LTC2965

RS

PS

R1

200kΩ

R2

91kΩ

R3

909kΩ

UV RISING THRESHOLD = 20V

UV FALLING THRESHOLD = 18.2V

R1

4.7kΩ

ENABLE

POWER GOOD

TO LOAD

GND

IN

OUT

SHDN

STATUS

LT4423

GND

IN

OUT

SHDN

STATUS

LT4423

TA = 105°C

TA = 90°C

TA = 80°C

TA = 70°C

IN = 12V

TJMAX = 125°C

DIODE CURRENT (A)

1.25

1.50

1.75

2.00

2.25

0.1

1

10