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Revision 2.11

15 - 19

AS1108

Data Sheet - Ty p i c a l A p p l i c a t i o n

4x8 LED Dot Matrix Driver

The application example in Figure 12 shows the AS1108 as a 4x8 LED dot matrix driver.

The LED columns have common cathodes and are connected to the DIG0:3 outputs. The rows are connected to the

segment drivers. Each of the 32 LEDs can be addressed separately. The columns are selected via the digits as listed

in Table 7 on page 8.

The Decode Enable Register (see page 9) must be set to ‘00000000’ as described in Table 9 on page 9. Single LEDs

in a column can be addressed as described in Table 12 on page 10, where bit D0 corresponds to segment G and bit

D7 corresponds to segment DP.

Note: For a multiple-digit dot matrix, multiple AS1108 devices must be cascaded.

Figure 12. Application Example as LED Dot Matrix Driver

Cascading Drivers

If more than 4 digits or 32 LEDs are needed, it is recommended to use the AS1106/AS1107, although several AS1108

devices can be cascaded.

The example in Figure 4 drives 2 dot matrix digits using a 4-wire microprocessor interface. All Scan-Limit Registers

should be set to the same value so that one display will not appear brighter than the other.

For example, to display 6 digits, set both Scan-Limit Registers to display 3 digits so that both displays have a 1/3 duty

cycle per digit. If 5 digits are needed, set both Scan-Limit Registers to display 3 digits and leave one digit unconnected.

Otherwise, if one driver is set to display 3 digits and the other to display 2 digits one display will appear brighter

because its duty cycle per digit will be 1/2 and the other display’s duty cycle will be 1/3.

Note: Refer to No-Op Register (0xX0) on page 12 for additional information.

SEG G

DIG0:3

DIN

GND

GND

LOAD/CSN

CLK

SEG A:G

SEG DP

9.53k

Ω

DIG0:3

DIN

GND

GND

LOAD/CSN

CLK

SEG A:G

SEG DP

9.53k

Ω

DOUT

4x8 LED

Dot Matrix

Diode Arrangement

Micro-

Processor

SEG A

SEG DP

SEG B

SEG C

SEG D

SEG E

SEG F

SEG G

4x8 LED

Dot Matrix

SEG A

SEG DP

SEG B

SEG C

SEG D

SEG E

SEG F

AS1108

AS1108