Rev. 10/24/00

V

OUT

GND

SPX5205

Top View

EN

BYP

(Optn)

V

IN

+

+

Fig. 1

1

2

3

5

4

Hi-ON

Lo-OFF

SPX5205

Application Hints

The SPX5205 requires an output capacitor for device stability.

The value required varies greatly depending upon the

application circuit.

The high frequency characteristics of

electrolytic capacitors depend greatly on the type and also on

the manufacturer. Sometimes bench testing is the only means

to determine the proper capacitor type and value. The high

quality 2.2

µF aluminum electrolytic capacitor covers all

general application circuits; this stability can be obtained with

a tantalum electrolytic value of 1

µF.

In general, linear regulator stability decreases with higher

output currents.

In most applications the SPX5205 is

operating at few milliamps. In these applications the output

capacitance can be further reduced. For example, when the

regulator is running at 10mA output current the output

capacitance value is half compared to the same regulator

that is running at 150mA.

With the SPX5205 adjustable regulator, the minimum value

of output capacitance is a function of the output voltage.

The value decreases with higher output voltages, since the

closed loop gain is increased.

Typical Applications Circuits

The SPX5205 provides access to the internal reference. A 10

µF capacitor on the BYP pin will provide a significant reduction in

output noise. This pin may be left unconnected if the output noise is not a major concern. The SPX5205 start-up speed is inversely

proportional to the size of this capacitor. Applications requiring a slow ramp-up of output voltage should consider larger values of

Figure 1 shows SPX5205 standard application circuit. The EN pin is pulled high (>2.0V) to enable the regulator. To disable the

regulator, EN < 0.6V.

The SPX5205 in figure 2 shows adjustable output voltage configuration. Two resistors set the output voltage. The formula for output

voltage is:

Resistor values are not critical as the ADJ pin has high input impedance, for best results use resistors of 47k

Ω or less. A capacitor

from ADJ to ground will provide improved noise performance.

V

IN

V

OUT

GND

Top View

EN

Byp

(Optn)

+

+

ADJ

R1

R2

Fig. 2

Hi-ON

Lo-OFF

1

2

3

4

5

SPX5205

R1

R2