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SPX29301

3A High Current, Low Dropout Voltage Regulator

Signal Processing Technologies 

The SPX29300/01/02/03 incorporates pro-

tection 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 lim-

iting 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,

T

A

=

50°C,

θHA=

1°C/W,

θCH=

2°C/W,

and θJC= 3C°/W, where:

T = ambient temperature,

A

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:

PD = (VIN – VOUT) * IOUT = 7.5W.

And the junction temperature is calculated as

TJ = TA + PD * (θHA + θCH + θJC) or

T

J

=

50

+

7.5

*

(1+2+3)

=

95°C

Reliable operation is insured.

Capacitor Requirements

The output capacitor is needed to insure sta-

bility and minimize the output noise. The value

of the capacitor varies with the load. However,

a minimum value of 10μF aluminum 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 capacit-

or 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)].

A minimum value of 10kohms is recommen-

ded for R2 with a range between 10kohms and

47 kohms.

Date: 9/5/06 Rev C

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

5

© 2006 Sipex Corporation

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