www.austriamicrosystems.com/LED-Driver-ICs/AS1106_07

Revision 2.29

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AS1106, AS1107

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9 Application Information

9.1 Supply Bypassing and Wiring

In order to achieve optimal performance the AS1106/AS1107 should be placed very close to the LED display to minimize effects of

electromagnetic interference and wiring inductance.

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

supply ripple (see Figure 14 on page 16).

Note:

Both GND pins must be connected to ground.

9.2 Selecting RSET Resistor Value and Using External Drivers

Brightness of the display segments is controlled via RSET. The current that flows between VDD and ISET defines the current that flows through

the LEDs.

Segment current is about 200 times the current in ISET. Typical values for RSET for different segment currents, operating voltages, and LED

voltage drop (VLED) are given in Tables 19 - 23. The maximum current the AS1106/AS1107 devices can drive is 40mA. If higher currents are

needed, external drivers must be used, in which case it is no longer necessary that the devices drive high currents.

In cases where the devices only drive a few digits, Table 16 specifies the maximum currents, and RSET must be set accordingly.

Note:

The display brightness can also be logically controlled (see Intensity Control Register (0xXA) on page 12).

Table 19. RSET vs. Segment Current and LED Forward Voltage, VDD = 2.7V

ISEG (mA)

VLED(V)

1.5

2.0

40

5k

Ω

4.4k

Ω

30

6.9k

Ω

5.9k

Ω

20

10.7k

Ω

9.6k

Ω

10

22.2k

Ω

20.7k

Ω

Table 20. RSET vs. Segment Current and LED Forward Voltage, VDD = 3.3V

ISEG (mA)

VLED(V)

1.5

2.0

2.5

40

6.7k

Ω

6.4k

Ω

5.7k

Ω

30

9.1k

Ω

8.8k

Ω

8.1k

Ω

20

13.9k

Ω

13.3k

Ω

12.6k

Ω

10

28.8k

Ω

27.7k

Ω

26k

Ω

Table 21. RSET vs. Segment Current and LED Forward Voltage, VDD = 3.6V

ISEG (mA)

VLED(V)

1.5

2.0

2.5

3.0

40

7.5k

Ω

7.2k

Ω

6.6k

Ω

5.5k

Ω

30

10.18k

Ω

9.8k

Ω

9.2k

Ω

7.5k

Ω

20

15.6k

Ω

15k

Ω

14.3k

Ω

13k

Ω

10

31.9k

Ω

31k

Ω

29.5k

Ω

27.3k

Ω

Table 22. RSET vs. Segment Current and LED Forward Voltage, VDD = 4.0V

ISEG (mA)

VLED(V)

1.5

2.0

2.5

3.0

3.5

40

8.6k

Ω

8.3k

Ω

7.9k

Ω

7.6k

Ω

5.2k

Ω

30

11.6k

Ω

11.2k

Ω

10.8k

Ω

9.9k

Ω

7.8k

Ω

20

17.7k

Ω

17.3k

Ω

16.6k

Ω

15.6k

Ω

13.6k

Ω

10

36.89k

Ω

35.7k

Ω

34.5k

Ω

32.5k

Ω

29.1k

Ω