sames
FEATURES
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SA8803
LIGHT EMITTING DIODE DRIVER
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Drives 24 LED's under control of Serial
Interface
Light Emitting Diode intensity
programmable using a single resistor
Automatic lamp test facility on reset
(MRST)
Minimal external components
LED intensity constant, regardless of
number of LED's illuminated
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11 Bit Information word controls up to
192 LED's (using eight SA8803s)
Readback of LED status
Requires a local clock of 8 times the
data rate
Constant current from power supply
option
PIN CONNECTIONS
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
LED 1
LED 2
is set according to the Status bit in the Control
LED 3
word.
LED 4
The LEDs are driven by banks of Constant
V EE
Current Sources in which the value of the
LED 5
SA8803
current in all six banks is set by a single
LED 6
LED 7
external resistor connected between pin
V
DD
INTENS and VEE. The total current drained
LED 8
by the device and the LEDs may be fixed at
LED 9
six times the LED current by connecting pin
CC to GND.
The status of all LEDs can be verified at any
DR-00593
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.
DOUT
DATA
V DD
AD 2
AD 1
AD 0
CC
6
5
4
3
2
1
44
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
MRST
42
GND
CLK
41
43
N.C.
40
39
38
37
36
35
34
33
32
31
30
29
TEST
LED 24
LED 23
LED 22
V EE
LED 21
LED 20
LED 19
V DD
LED 18
LED 17
25
26
27
28
INTENS
LED 14
LED 15
V EE
LED 11
LED 12
LED 13
LED 10
V EE
LED 16
V DD
1/10
REV. C
07-03-96
4159
PDS039-SA8803-001
SAMES [ SAMES ]
