SA8803 Datasheet, PDF (1/10 Pages) Sames – LIGHT EMITTING DIODE DRIVER

sames
SA8803
LIGHT EMITTING DIODE DRIVER
FEATURES
n Drives 24 LED's under control of Serial n 11 Bit Information word controls up to
Interface
192 LED's (using eight SA8803s)
n Light Emitting Diode intensity n Readback of LED status
programmable using a single resistor n Requires a local clock of 8 times the
n Automatic lamp test facility on reset
data rate
(MRST)
n Constant current from power supply
n Minimal external components
option
n LED intensity constant, regardless of
number of LED's illuminated
DESCRIPTION
PIN CONNECTIONS
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.
LED 1 ⁷
LED 2 8
LED 3 ⁹
LED 4 ¹⁰
V _EE 11
LED 5 ¹²
LED 6 ¹³
LED 7 14
V _DD ¹⁵
LED 8 ¹⁶
LED 9 17
6 5 4 3 2 1 44 43 42 41 40
39 _TEST
38 LED 24
37 _{LED 23}
36 _{LED 22}
SA8803
35 V _EE
34 _{LED 21}
33 _{LED 20}
32 LED 19
31 _{V DD}
30 _{LED 18}
29 LED 17
18 19 20 21 22 23 24 25 26 27 28
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.
4159
PDS039-SA8803-001
1/10
REV. C 07-03-96