5

Date: 5/25/04

SPX2810 1A Low Dropout Linear Regulator

© Copyright 2004 Sipex Corporation

PC BOARD

TOPSIDE COPPER

BACKSIDE COPPER

THERMAL RESISTANCE

JUNCTION TO AMBIENT

°C/W

2500

2500

2500

46

2500

1250

2500

47

2500

950

2500

49

2500

2500

0

51

2500

1800

0

53

1600

600

1600

55

2500

1250

0

58

2500

915

0

59

1600

600

0

67

900

240

900

72

900

240

0

85

Figure 8. 600mA Current Source

Figure 9. Typical Adjustable Regulator

Ripple Rejection

Ripple rejection can be improved by adding a

capacitor between the ADJ pin and ground as

shown in Figure 6. When ADJ pin bypassing is

used, the value of the output capacitor required

increases to its maximum. If the ADJ pin is not

bypassed, the value of the output capacitor can

be lowered to 10(F for an electrolytic aluminum

capacitor or 2.2

µF for a solid tantalum capacitor

(Fig 10). However the value of the ADJ-bypass

capacitor should be chosen with respectto the

following equation:

C = 1 / ( 6.28 * F

Where C = value of the capacitor in Farads

(select an equal or larger standard value),

F

R

If an ADJ-bypass capacitor is used, the

amplitude of the output ripple will be inde-

pendent of the output voltage. If an ADJ-

bypass capacitor is not used, the output ripple

will be proportional to the ratio of the output

voltage to the reference

voltage:

M = V

Where M = multiplier for the ripple seen when

the ADJ pin

is optimally bypassed.

V

TYPICAL APPLICATION CIRCUITS

LOAD

ADJ

SPX2810

V

IN

C

1

OUT

IN

4.7µF

C

2

I

OUT

R

1

V

REF

R

1

I

+

IN

OUT

SPX2810

R

1

R

2

C

2

V

V

REF

50µA

ADJ

4.7µF +