AS1108_1 AMSCO [austriamicrosystems AG], AS1108_1 Datasheet - Page 11

• Manufacturer Part Number: AS1108_1
• Description: 4-Digit LED Display Driver
• Manufacturer: AMSCO [austriamicrosystems AG]

AS1108
Data Sheet - D e t a i l e d D e s c r i p t i o n
Intensity Control Register (0xXA)
The brightness of the display can be controlled by digital means using the Intensity Control Register and by analog
means using R
Display brightness is controlled by an integrated pulse-width modulator which is controlled by the lower-nibble of the
Intensity Control Register. The modulator scales the average segment-current in 16 steps from a maximum of 31/32
down to 1/32 of the peak current set by R
Table 14. Intensity Register Format (Address (HEX) = 0xXA))
Scan-Limit Register (0x0B)
The Scan-Limit Register controls which of the digits are to be displayed. When all 4 digits are to be displayed, the
update frequency is typically 1600Hz. If the number of digits displayed is reduced, the update frequency is increased.
The frequency can be calculated using 8fOSC/N, where N is the number of digits. Since the number of displayed digits
influences the brightness, R
fewer than 4 digits are used.
Note: To avoid differences in brightness this register should not be used to blank parts of the display (leading zeros).
Table 15. Scan-Limit Register Format (Address (HEX) = 0xXB))
Table 16. Maximum Segment Current for 1-, 2-, or 3-Digit Displays
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Display digit 0 only (see Table 16)
Display digits 0:1 (see Table 16)
Display digits 0:2 (see Table 16)
Number of Digits Displayed
31/32 (max on)
1/32 (min on)
Duty Cycle
Display digits 0:3
AS1108
11/32
13/32
15/32
17/32
19/32
21/32
23/32
25/32
27/32
29/32
3/32
5/32
7/32
9/32
Scan Limit
SET
(see Selecting RSET Resistor Value and Using External Drivers on page 13).
1
2
3
SET
should be adjusted accordingly. Table 16 lists the maximum allowed current when
HEX Code
0xXC
0xXD
0xXA
0xXB
0xXE
0xXF
0xX0
0xX1
0xX2
0xX3
0xX4
0xX5
0xX6
0xX7
0xX8
0xX9
HEX Code
SET
0xX0
0xX1
0xX2
0xX3
.
Maximum Segment Current (mA)
D7
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Revision 2.11
D7
X
X
X
X
D6
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
10
20
30
D6
X
X
X
X
D5
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
D5
X
X
X
X
Register Data
D4
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Register Data
D4
X
X
X
X
D3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
D3
X
X
X
X
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D2
0
0
0
0
D1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D1
0
0
1
1
11 - 19
D0
D0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1