SC573 datasheet(14/17 Pages) SEMTECH

14 / 17 page

SC573

Final Rev2.1

Applications Information (continued)

Example

A SC573LH is used to provide an output voltage of 3.3V

at 150mA. The input voltage is 4.2V, and the ambient

temperature of the system is 60°C.

D= 0.15 X (4.2 – 3.3)

= 0.135W

and

J = 60°C + (0.135W x 262°C/W*) = 95.4°C

This calculation shows that the junction temperature is

about 95°C and is well below the allowed maximum

junction temperature of 125°C for this power dissipation.

Layout Considerations

The diagram in Figure 3 below illustrates proper layout of

a circuit. The layout considerations are listed below:

• Attach pin 2 (GND) of the device to a copper pad

with vias connected to the GND plane. This

enables better heat transfer from the device to

the PCB.

• Place the input and output capacitors close to

the device for optimal transient response and

device behavior. Extra copper trace length

between the device input and output to the

capacitor soldering pad introduces parasitic

inductance.

• Connect all ground connections of the input and

output capacitors directly to the ground plane

whenever possible to minimize ground potential

differences on the PCB. Shown in the evaluation

board layout below, the SC573 ground pins,

input and output capacitors are all connected to

the ground plane through vias.

Figure 3 — SC573 Layout Example

SC573 Datasheet(PDF) 14 Page - Semtech Corporation