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AS1106, AS1107
Datasheet - Application Information
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 mnimze effects of
electromagnetic interference and wiring inductance.
Furthermore, it is recommended to connect a 10μF electrolytic and a 0.1μF ceramc capacitor between pins V
DD
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 R
SET
Resistor Value and Using External Drivers
Brightness of the display segments is controlled via R
SET
. The current that flows between V
DD
and I
SET
defines the current that flows through
the LEDs.
Segment current is about 200 times the current in I
SET
. Typical values for R
SET
for different segment currents, operating voltages, and LED
voltage drop (V
LED
) are given in Tables 19 - 23. The maximumcurrent 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 maximumcurrents, and R
SET
must be set accordingly.
Note:
The display brightness can also be logically controlled (see Intensity Control Register (0xXA) on page 12).
Table 19. R
SET
vs. Segment Current and LED Forward Voltage, V
DD
= 2.7V
I
SEG
(mA)
V
LED
(V)
1.5
5k
Ω
6.9k
Ω
10.7k
Ω
22.2k
Ω
2.0
4.4k
Ω
5.9k
Ω
9.6k
Ω
20.7k
Ω
40
30
20
10
Table 20. R
SET
vs. Segment Current and LED Forward Voltage, V
DD
= 3.3V
I
SEG
(mA)
V
LED
(V)
2.0
6.4k
Ω
8.8k
Ω
13.3k
Ω
27.7k
Ω
1.5
6.7k
Ω
9.1k
Ω
13.9k
Ω
28.8k
Ω
2.5
5.7k
Ω
8.1k
Ω
12.6k
Ω
26k
Ω
40
30
20
10
Table 21. R
SET
vs. Segment Current and LED Forward Voltage, V
DD
= 3.6V
I
SEG
(mA)
V
LED
(V)
1.5
7.5k
Ω
10.18k
Ω
15.6k
Ω
31.9k
Ω
2.0
7.2k
Ω
9.8k
Ω
15k
Ω
31k
Ω
2.5
6.6k
Ω
9.2k
Ω
14.3k
Ω
29.5k
Ω
3.0
5.5k
Ω
7.5k
Ω
13k
Ω
27.3k
Ω
40
30
20
10
Table 22. R
SET
vs. Segment Current and LED Forward Voltage, V
DD
= 4.0V
I
SEG
(mA)
V
LED
(V)
2.5
7.9k
Ω
10.8k
Ω
16.6k
Ω
34.5k
Ω
1.5
8.6k
Ω
11.6k
Ω
17.7k
Ω
36.89k
Ω
2.0
8.3k
Ω
11.2k
Ω
17.3k
Ω
35.7k
Ω
3.0
7.6k
Ω
9.9k
Ω
15.6k
Ω
32.5k
Ω
3.5
5.2k
Ω
7.8k
Ω
13.6k
Ω
29.1k
Ω
40
30
20
10