5

FN7296.2

May 13, 2005

Pin Descriptions

20-PIN SO

(0.300”)

28-PIN

HTSSOP

PIN NAME

PIN FUNCTION

1

1

VREF

Bandgap reference bypass capacitor; typically 0.1µF to SGND

2

2

SGND

Control circuit negative supply or signal ground

3

3

COSC

Oscillator timing capacitor (see performance curves)

4

4

VDD

Control circuit positive supply; normally connected to VIN through an RC filter

5

5

VTJ

Junction temperature monitor; connected with 2.2nF to 3.3nF to SGND

6, 7

6, 7, 8, 9

PGND

Ground return of the regulator; connected to the source of the low-side synchronous NMOS

power FET

8

10, 11

VIN

Power supply input of the regulator; connected to the drain of the high-side NMOS power FET

9

13

STP

Auxiliary supply tracking positive input; tied to regulator output to synchronize start up with a

second supply; leave open for stand alone operation; 2µA internal pull down current

10

14

STN

Auxiliary supply tracking negative input; connect to output of a second supply to synchronize

start up; leave open for stand alone operation; 2µA internal pull up current

11, 12, 13

15, 16

PGND

Ground return of the regulator; connected to the source of the low-side synchronous NMOS

power FET

14, 15

18, 19, 20, 21,

22, 23

LX

Inductor drive pin; high current output whose average voltage equals the regulator output

voltage

16

24

VHI

Positive supply of high-side driver; boot strapped from VDRV to LX with an external 0.22µF

capacitor

17

25

VDRV

Positive supply of low-side driver and input voltage for high side boot strap

18

26

PG

Power good window comparator output; logic 1 when regulator output is within ±10% of target

output voltage

19

27

FB

Voltage feedback input; connected to external resistor divider between VOUT and SGND; a

125nA pull-up current forces VOUT to SGND in the event that FB is floating

20

28

EN

Chip enable, active high; a 2µA internal pull up current enables the device if the pin is left open;

a capacitor can be added at this pin to delay the start of converter

Typical Performance Curves (20 Pin SO Package)

NOTE: The 28-Pin HTSSOP Package Offers Improved Performance

FIGURE 2. EL7563CRE EFFICIENCY

100

95

90

85

80

75

70

0

1

22.5

33.5

4

0.5

1.5

100

95

90

85

80

75

70

65

60

0.1

0.6

1.1

1.6

2.1

2.6

3.1

3.6

4

EL7563