WEITRON

http://www.weitron.com.tw

WT1117A

8/11

Rev-A 18-Oct-06

(a) Fixed Version

(b) Adjustable Version

V

IN

V

OUT

C

ADJ

WT1117A-Adj

ADJ

V

IN

V

OUT

C1

C2

R1

R2

WT1117A-3.3

GND

V

IN

V

OUT

C1

IN4002

C2

V

IN

V

OUT

IN4002

When large external capacitors are used with most linear regulator, it is wise to add protection diodes. If the input voltage

of the regulator is shorted, the output capacitor will discharge into the output of the regulator. The discharge current

In the WT1117A linear regulators, the discharge path is through a large junction, and protection diodes are normally not

needed. However, damage can occur if the regulator is used with large output capacitance values and the input voltage

is instantaneously shorted to ground. In this case, a diode connected as shown above in Figure 2.

The WT1117A are three terminal regulators. For which, they cannot provide true remote load sensing. Load regulation

is limited by the resistance of the conductors connecting the regulator to the load. For best results the WT1117A

should be connected are as shown in Figure 3.

Protection Diodes

Output Voltage Sensing

Calculating Power Dissipation and Heat Sink Requirements

WT1117A-3.3

V

IN

V

OUT

R

LOAD

R

C

GND

V

IN

Conductor

Parasitic

Resistance

(a) Fixed Version

(b) Adjustable Version

WT1117A-Adj

ADJ

V

OUT

V

IN

V

IN

R

C

R

LOAD

R1

R2

Conductor

Parasitic

Resistance

Figure3

The WT1117A precision linear regulators include thermal shutdown and current limit circuitry to protect the devices.

However, high power regulators normally operate at high junction temperatures. It is important to calculate the power

dissipation and junction temperatures accurately to be sure that you use and adequate heat sink. The case is connected

be used with high current regulators like the WT1117A.