5

FN7297.3

May 9, 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

FIGURE 1. EL7564CM EFFICIENCY

FIGURE 2. EL7564CRE EFFICIENCY

100

60

65

70

75

85

95

04

3.5

3

2.5

2

1

0.5

1.5

80

90

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

4.1

EL7564