4

Date: 5/25/04

SPX2810 1A Low Dropout Linear Regulator

© Copyright 2004 Sipex Corporation

Output Capacitor

To ensure the stability of the SPX1202, an

output capacitor of at least 10

µF (tantalum or

ceramic) or 50

µF (aluminum) is required. The

value may change based on the application

requirements of the output load or temperature

range. The value of ESR can vary based on the

type of capacitor used in the applications. The

recommended value for ESR is 0.5

Ω or less. A

larger value of output capacitance (up to 100

µF)

can improve the load transient response.

SOLDERING METHODS

The SPX2810 SOT-223 package is designed to

be compatible with infrared reflow or vapor-

phase reflow soldering techniques. During sol-

dering, the non-active or mildly active fluxes

may be used. The SPX2810 die is attached to

the heatsink lead which exits opposite the input,

output, and ground pins.

Hand soldering and wave soldering should be

avoided since these methods can cause damage

to the device with excessive thermal gradients

on the package. The SOT-223 recommended

soldering method are as follows: vapor phase

reflow and infrared reflow with the component

preheated to within 65

°C of the soldering tem-

perature range.

THERMAL CHARACTERISTICS

The thermal resistance of SPX2810 depends on

type of package and PC board layout as shown

in Table 1. The SPX2810 features the internal

thermal limiting to protect the device during

overload conditions. Special care needs to be

taken during continuous load conditions such

that the maximum junction temperature does

not exceed 125

°C. Thermal protection is acti-

vated at >144

°C and deactiviated at <137°C.

Taking the FR-4 printed circuit board and 1/16

thick with 1 ounce copper foil as an experiment,

the PCB material is effective at transmitting

heat with the tab attached to the pad area and a

ground plane layer on the backside of the sub-

strate. Refer to table 1 for the results of the

experiment.

The thermal interaction from other components

in the application can effect the thermal resis-

tance of the SPX2810. The actual thermal resis-

tance can be determined with experimentation.

SPX2810 power dissipation is calculated as

follows:

P

Maximum Junction Temperature range:

T

Thermal Resistance)

Although the SPX2810 offers some limiting

circuitry for overload conditions, it is still nec-

essary to insure that maximum junction

tepmerature is not exceeded. Heat will flow

through the lowest resistance path, in this case

the junction to case. Therfore proper mounting

of the regulator to the board is critical. The case

of the device is electrically connected to the

output. If the case must be electrically isolated,

a thermal nonconductive spacer should be used

between the case and the board. It thermal resis-

tance must be taken into account.

For example:

V

Theta

theta

Power dissipation is calculated as

P

Junction Temperature will be

T

T

Figure 7. Substrate Layout for SOT-223 for thermal

experiment.

50 X 50mm

35 X 17mm

16 X 10mm

APPLICATION INFORMATION