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FOD3181 Rev. 1.0.3

Reflow Profile

Output Power Derating

The maximum package power dissipation is 295mW. The pack-

age is limited to this level to ensure that under normal operating

conditions and over extended temperature range that the semi-

conductor junction temperatures do not exceed 125°C. The

package power is composed of three elements; the LED, static

operating power of the output IC, and the power dissipated in

the output power MOSFET transistors. The power rating of the

output IC is 250mW. This power is divided between the static

maximum condition is valid over the operational temperature

range of -40°C to +100°C. Under these maximum operating

conditions, the output of the power MOSFET is allowed to dissi-

pate 100mW of power.

The absolute maximum output power dissipation versus ambi-

ent temperature is shown in Figure 12. The output driver is

capable of supplying 100mW of output power over the tempera-

ture range from -40°C to 87°C. The output derates to 90mW at

the absolute maximum operating temperature of 100°C.

The output power is the product of the average output current

current flowing in the output. The duty factor is the ratio of the

‘on’ time of the output load current divided by the period of the

output load current of 200mA. The load duty factor is a ratio of

the average output time of the power MOSFET load circuit and

period of the driving frequency.

The maximum permissible, operating frequency is determined

by the load supplied to the output at its resulting output pulse

width. Figure 13 shows an example of a 0.03µF gate to source

capacitance with a series resistance of 40

Ω. This reactive load

results in a composite average pulse width of 1.5µs. Under this

load condition it is not necessary to derate the absolute maxi-

mum output current out to 250kHz.

• Peak reflow temperature: 260 C (package surface temperature)

• Time of temperature higher than 183 C for 160 seconds or less

• One time soldering reflow is recommended

245 C, 10–30 s

Time (Minute)

0

300

250

200

150

100

50

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Time above 183C, <160 sec

Ramp up = 2–10C/sec

260 C peak

Fig. 12 Absolute Maximum Power Dissipation

vs. Ambient Temperature

-40

-20

0

20

40

60

80 85

0.15

0.1

0.05

0

LED Power = 45mW

F – Frequency (kHz)

0

0.5

1

1.5

110

250

Fig. 13 Output Current Derating vs. Frequency

Load = .03µF +40Ω

LED Duty Factor = 50%

Output Pulse Width = 1.5µs