www.austriamicrosystems.com/LED-Driver-ICs/AS1115

Revision 1.08

20 - 25

AS1115

Datasheet - Ty p i c a l A p p l i c a t i o n

8x8 Dot Matrix Mode

The application example in Figure 27 shows the AS1115 in the 8x8 LED dot matrix mode.

The LED columns have common cathodes and are connected to the DIG0:7 outputs. The rows are connected to the segment drivers. Each of

the 64 LEDs can be addressed separately. The columns are selected via the digits as listed in Table 6 on page 12.

The Decode Enable Register (see page 13) must be set to ‘00000000’ as described in Table 8 on page 13. Single LEDs in a column can

be addressed as described in Table 11 on page 15, where bit D0 corresponds to segment G and bit D7 corresponds to segment DP.

Figure 27. Application Example as LED Dot Matrix Driver

Keyscan

The key readback of the AS1115 can be used either for push buttons as well as switches. If only a single key is pressed (shorted) at a time no

additional diodes are required. If a detection of multiple simultaneous keystrokes is required diodes within the keypath, as shown in Figure 28,

are required. Pressing multiple keys without the diodes would result in ambiguous results. Since KEYA and KEYB have independent inputs only

keys on the same path are affected.

Figure 28. Keyscan Configuration

Note:

If the blink_en bit (bit D4 in the Feature Register 0x0E) is set to ‘1’, the keyscan is not returning a valid value.

Supply Bypassing and Wiring

In order to achieve optimal performance the AS1115 should be placed very close to the LED display to minimize effects of electromagnetic inter-

ference and wiring inductance.

Furthermore, it is recommended to connect a 10 F and a 0.1 F ceramic capacitor between pins VDD and GND to avoid power supply ripple

(see Figure 27)

.

Diode Arrangement

DIG0 to

DIG7

SEG A to G

SEP DP

AS1115

SDA

SCL

IRQ

VDD

ISET

SDA

IRQ

GND

SCL

2.7 to 5V

9.53k

Ω

µP

KEYA

KEYB

SEGA

SEGB

SEGC

SEGD

SEG E

SEGF

SEGG

SEGDP

IRQ

Diodes are optional and only required if multiple keystrokes must be

detected simultaneously.

If I²C Self-Addressing is used these two keys cannot be used for read-

back and must be either hard wired opened or shorted.

A short writes a logical “0” whereas an open writes a logical “1” as

address bit.