SA8803 Datasheet | Sames

sames SA8803 LIGHT EMITTING DIODE DRIVER Features n Drives 24 LED's under control of Serial n 11 Bit Information word controls up to 192 LED's (using eight SA8803s) Interface n Light Emitting Diode intensity n Readback of LED status programmable using a single resistor n Requires a local clock of 8 times the data rate n Automatic lamp test facility on reset (MRST) n Constant current from power supply option n Minimal external ponents n LED intensity constant, regardless of number of LED's illuminated 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 prises 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 TEST addressed and the state of the selected LED LED 1 LED 2 LED 24 is set according to the Status bit in the Control LED 3 LED 23 word. LED 22 LED 4 V EE The LEDs are driven by banks of Constant V EE LED 21 Current Sources in which the value of the LED 5 SA8803 LED 20 current in all six banks is set by a single LED 6 LED 7 LED 19 external resistor connected between pin V V DD DD INTENS and VEE. The total current drained LED 8 LED 18 by the device and the LEDs may be fixed at LED 9 LED 17 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 0 MRST AD 2 AD 1 7 8 9 N.C. 40 28 39 38 37 36 35 34 33 32 10 11 12 13 14 15 16 17 31 30 29 INTENS LED 14 LED 15 V EE LED 11 LED...