FEATURES

n

Drives 24 LED's under control of Serial

Interface

n

Light

Emitting

Diode

intensity

programmable using a single resistor

n

Automatic lamp test facility on reset

(MRST)

n

Minimal external components

n

LED intensity constant, regardless of

number of LED's illuminated

sames

PDS039-SA8803-001

REV. C

07-03-96

LIGHT EMITTING DIODE DRIVER

4159

SA8803

1/10

n

11 Bit Information word controls up to

192 LED's (using eight SA8803s)

n

Readback of LED status

n

Requires a local clock of 8 times the

data rate

n

Constant current from power supply

option

DESCRIPTION

The block Diagram of the SA8803 is shown in

Fig. 1. A control word is clocked into the

device via the DATA pin with a local clock

provided to pin CLK.

The control word

comprises a 3-bit chip address, a 5-bit LED

address and a Status (on/off) bit. Provided

that the Chip Adress matches the setting on

pins AD0..AD2 then the LED State Register is

addressed and the state of the selected LED

is set according to the Status bit in the Control

word.

The LEDs are driven by banks of Constant

Current Sources in which the value of the

current in all six banks is set by a single

external resistor connected between pin

INTENS and VEE. The total current drained

by the device and the LEDs may be fixed at

six times the LED current by connecting pin

CC to GND.

The status of all LEDs can be verified at any

time by pulling the TEST pin low. When tis

happens the contents of the LED Status

Register are clocked out of the SA8803 on the

pin DOUT. An additional test feature is that

al LEDs are illuminated for a short period after

power up to simplify system testing.

PIN CONNECTIONS

23

SA8803

1

LED 7

DR-00593

LED 8

LED 9

V DD

18

19

15

16

17

20

21

22

V EE

LED 4

LED 5

LED 6

LED 1

LED 2

LED 3

10

11

12

13

14

7

8

9

65

43

2

LED 19

24

25

26

27

28

29

30

31

V

LED 18

LED 17

DD

44

43

42

32

33

34

35

36

37

38

39

41

40

V

LED 21

LED 20

EE

LED 22

TEST

LED 24

LED 23