LTC7151S datasheet(37/44 Pages) AD

37 / 44 page

Data Sheet

LT83203/LT83205

analog.com

Rev. B

37 of 44

Thermal Considerations

For higher ambient temperatures, care should be taken in the layout of the PCB to ensure good heat sinking of the

LT83203/LT83205. The exposed pad on the bottom of the package should be soldered to a ground plane. This ground

should be connected to large copper layers below with thermal vias; these layers spread heat dissipated by the

LT83203/LT83205. Placing additional vias can reduce thermal resistance further. The maximum load current should

be derated as the ambient temperature approaches the maximum junction rating. Power dissipation within the

LT83203/LT83205 can be estimated by calculating the total power loss from an efficiency measurement and

subtracting the inductor loss. The die temperature is calculated by multiplying the LT83203/LT83205 power

dissipation by the thermal resistance from junction to ambient.

The internal overtemperature protection monitors the junction temperature of the LT83203/LT83205. If the junction

temperature reaches approximately 165°C, the LT83203/LT83205 stops switching and indicates a fault condition

until the temperature drops about 5°C cooler.

The temperature rise of the LT83203/LT83205 is at its worst when operating at high load, high VIN, and high switching

frequency. If the case temperature is too high for a given application, then either VIN, switching frequency, or load

current can be decreased to reduce the temperature to an appropriate level. Figure 58 shows examples of how case

temperature rise can be managed by reducing load.

The LT83203/LT83205’s top switch current limit decreases with higher duty cycle operation for slope compensation.

This also limits the output current the LT83203/LT83205 can deliver for a given application. See curve in Typical

Performance Characteristics.

Figure 58. LT83203/LT83205 Case Temperature Rise

DEMO BOARD, ON STILL AIR

VIN = 12V

VOUT = 1V

fSW = 2MHz

LOAD CURRENT (A)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

LTC7151S Datasheet(PDF) 37 Page - Analog Devices