SI-3120KM

1 A, Low-Dropout,

12 V Regulator

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036

Linear

Regulators

6

Determination of DC Input Voltage. The minimum

input voltage V

fixed output voltage and the maximum rated dropout

voltage. If setting the output voltage lower than 2.0 V, the

minimum input voltage should be more than 2.4 V.

Overcurrent Protection. The SI-3000KM series has a

built-in fold-back type overcurrent protection circuit, which

limits the output current at a start-up mode. It thus cannot

be used in applications that require current at the start-up

mode such as:

(1) constant-current load,

(2) power supply with positive and negative outputs to

common load (a center-tap type power supply), or

(3) raising the output voltage by putting a diode or a

resistor between the device ground and system ground.

Thermal Protection. Circuitry turns off the pass

transistor when the junction temperature rises above 135°C.

It is intended only to protect the device from failures due to

excessive junction temperatures and should not imply that

output short circuits or continuous overloads are permitted.

APPLICATIONS INFORMATION (cont.)

Heat Radiation and Reliability. The reliability of the

IC is directly related to the junction temperature (T

operation. Accordingly, careful consideration should be

given to heat dissipation.

The inner frame on which the integrated circuit is mounted

is connected to the GND terminal (pin 3). Therefore, it is

very effective for heat radiation to enlarge the copper area

that is connected to the GND terminal. The graph illus-

trates the effect of the copper area on the junction-to-

The junction temperature (T

either of the following equations:

T

or

T

where P