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SPX29302AT5-L

3A High Current, Low Dropout Voltage Regulator Adjustable & Fixed Output, Fast Response Time

Signal Processing Technologies 

The SPX29300/01/02/03 incorporates protec-

tion against over-current faults, reversed load

insertion, over temperature operation, and

positive and negative transient voltage.

Thermal Considerations

Although the SPX29300/01/02/03 offers

limiting circuitry for overload conditions, it is

still necessary to insure that the maximum

junction temperature is not exceeded in the

application. Heat will flow through the lowest

resistance path, the junction-to-case path. In

order to insure the best thermal flow of the

component, proper mounting is required.

TO-220 Design Example:

Assume that VIN = 10V, VOUT = 5V, IOUT =

1.5A, TA = 50°C, θHA= 1°C/W, θCH= 2°C/W,

and θJC= 3C°/W, where:

TA = ambient temperature,

θHA= heatsink to ambient thermal

resistance

θCH= case to heatsink thermal

resistance

θJC = junction to case thermal

resistance

The power calculated under these conditions

is:

P = (V – V ) * I = 7.5W.

D

IN

OUT

OUT

And the junction temperature is calculated as

T

J

=

T

A

+

P

D

*

(θHA

+

θCH

+ θJC) or

TJ = 50 + 7.5 * (1+2+3) = 95°C

Reliable operation is insured.

Capacitor Requirements

The output capacitor is needed to insure

stability and minimize the output noise. The

value of the capacitor varies with the load.

However, a minimum value of 10µF alumi-

num capacitor will guarantee stability over all

load conditions. A tantalum capacitor is

recommended if a faster load transient

APPLICATION INFORMATION

response is needed. If the power source has a

high AC impedance, a 0.1µF ceramic capaci-

tor between input & ground is recommended.

Minimum Load Current

To ensure a proper behavior of the regulator

under light load, a minimum load of 5mA for

SPX29300/01/02/03 is required.

Adjustable Regulator Design

The SPX29302/03 are adjustable regulators

that can be programmed to any value between

1.25V and 16V using 2 resistors, R1 and R2.

The relationship between the resistors is:

R1 = R2(Vout/1.240-1).

Error Flag

The SPX29301/03 features an error flag that

indicates either an over current or under

voltage condition. The flag output goes low,

sinking 10mA when either condition occurs.

Enable Input

The SPX29301/02 have an Enable function

that switches the regulator on and off. Their

thresholds are TTL compatible. When the

regulator is active, approximately 20 uA flows

through the Enable pin.

Typical Application Circuits

Figure 1 represents at typical fixed output

regulator. Figure 2 represents an adjustable

output regulator. The values of R1 and R2 set

the output voltage value as follows:

VOUT =VREF * [1 + (R1/R2)].

For best results, the total series resistance

should be small enough to pass a minimum

regulator load current of 5 mA. A minimum

value of 10kohms is recommended for R2

with a range between 10kohms and 47 kohms.

Date: 5/25/04

SPX29300/01/02/03 3A Low Dropout Voltage Regulator

5

© Copyright 2004 Sipex Corporation

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