MIC4802 datasheet(9/12 Pages) MICREL

Part #	MIC4802

Description	High Efficiency 800mA Single Channel Linear WLED Driver with Ultra Fast PWM??Control

PDF	12 Pages

Scroll/Zoom	100%

Manufacturer	MICREL [Micrel Semiconductor]

Direct Link	http://www.micrel.com

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9 / 12 page

Micrel Inc.

MIC4802

January 2011

M9999-013111-B

Figure 7. PWM Signal at 20% Duty Cycle (Iavg = 160mA)

Figure 8. PWM Signal at 50% Duty Cycle (Iavg = 400mA)

Figure 9. PWM Signal at 80% Duty Cycle (Iavg = 640mA)

Thermal Consideration

The MIC4802 thermal considerations involve calculating

the junction temperature based on the voltage drop

across the package and the LED current. The voltage

drop across the package is equal to the voltage at D1

with respect to ground times the LED current.

PLOSS = ILED * VD1

The temperature rise (ΔT) is calculated:

ΔT = PLOSS * θJA

Assuming the ILED is 800mA and VD1 is 500mV at 20°C

room temperature, we can calculate the junction

temperature:

TJ = TA + ΔT

TJ = 20°C + 0.4W * 41°C/W

TJ = 20°C + 16.4°C = 36.4°C

The junction temperature will be 36.4°C.

MIC4802 Datasheet(PDF) 9 Page - Micrel Semiconductor