AS1108
Datasheet - Typical Application
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 9.
The Decode Enable Register (see page 10) must be set to ‘00000000’ as described in Table 9 on page 10. Single
LEDs in a column can be addressed as described in Table 12 on page 11, 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
4x8 LED
4x8 LED
Dot Matrix
Dot Matrix
Diode Arrangement
SEG G
SEG F
SEG E
SEG G
SEG F
SEG E
SEG D
SEG C
SEG B
SEG D
SEG C
SEG B
SEG A
SEG DP
SEG A
SEG DP
SEG A:G DIG0:3
SEG DP
DOUT
SEG A:G DIG0:3
SEG DP
AS1108
AS1108
V
BAT
VBAT
VDD
VDD
DIN
DIN
Micro-
Processor
LOAD/CSN
CLK
LOAD/CSN
CLK
9.53kΩ
9.53kΩ
ISET
ISET
GND
GND
GND
GND
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 13 for additional information.
www.austriamicrosystems.com/LED-Driver-ICs/AS1108
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