1) To meet the minimum load current (>10mA) requirement, R1 is recommended to be 125ohm or lower. As LR1117C-ADJ

can keep itself stable at load current about 2mA, R1 is not allowed to be higher than 625ohm.

2)

THERMAL CONSIDERATIONS

We have to take heat dissipation into great consideration when output current or differential voltage of input and

output voltage is large. Because in such cases, the power dissipation consumed by LR1117 is very large. LR1117 series

uses SOT-223 package type and its thermal resistance is about 20°C/W. And the copper area of application board can

affect the total thermal resistance. If copper area is 5cm*5cm (two sides), the resistance is about 30°C/W. So the total

thermal resistance is about 20°C/W + 30°C/W. We can decrease total thermal resistance by increasing copper area in

application board. When there is no good heat dissipation copper are in PCB, the total thermal resistance will be as

high as 120°C/W, then the power dissipation of LR1117 could allow on itself is less than 1W. And furthermore, LR1117

will work at junction temperature higher than 125°C under such condition and no lifetime is guaranteed.

TYPICAL PERFORMANCE CHARACTERISTICS

T=25°C unless specified.

Line Regulation

Load Regulation

0

0.3

0.6

0.9

1.2

1.5

0

2

4

6

8

10

12

14

Vin (V)

LC1117-ADJ Vout Vs. Vin

0

0.3

0.6

0.9

1.2

1.5

0

0.2

0.4

0.6

0.8

1

1.2

Iout (A)

LC1117-ADJ Vout Vs. Iout

Dropout Voltage

Thermal performance with OTP

0

0.3

0.6

0.9

1.2

1.5

0

0.2

0.4

0.6

0.8

1

1.2

Iout (A)

LC1117-ADJ Dropout Vs. Iout

0

0.3

0.6

0.9

1.2

1.5

-50

0

50

100

150

200

Temperature (C)

LC1117-ADJ Vout Vs. Temp

LESHAN RADIO COMPANY, LTD.

Feb 2011 Ver1.2

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