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AS1105 Serially interfaced 4-digit LED driver datasheet
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A S 110 5
Serially Interfaced, 4-Digit LED Driver
1 General Description
The AS1105 is an LED driver for 7-segment numeric displays of up
to 4 digits. The AS1105 can be programmed via a conventional 4-
wire serial interface.
The device includes a BCD code-B decoder, a multiplex scan
circuitry, segment and display drivers, and a 32-bit memory. The
memory is used to store the LED settings, so that continuous
reprogramming is not necessary.
Every individual segment can be addressed and updated separately.
Only one external resistor is required to set the current through the
LED display.
Brightness can be controlled either in an analog or digital way. The
user can choose the internal code-B decoder to display numeric
digits or to address each segment directly.
The AS1105 features an extremely low shutdown current of only
20µA and an operational current of less than 500µA. The number of
visible digits can be programmed as well.
The AS1105 can be reset by software and an external clock can be
used. Several test modes support easy debugging.
AS1105 is offered in a 20-pin SOIC package.
2 Key Features
Cost effective version of AS1100 functionality for applications
up to 4-Digits
10MHz Serial Interface
Individual LED Segment Control
Decode/No-Decode Digit Selection
20µA Low-Power Shutdown (Data Retained)
Extremely low Operating Current 0.5mA in open loop
Digital and Analog Brightness Control
Display Blanked on Power-Up
Drive Common-Cathode LED Display
Software Reset
Optional External clock
20-pin SOIC Package
3 Applications
The AS1105 is an ideal solution for Bar-Graph Displays, Industrial
Controllers, Panel Meters, LED Matrix Displays and White Goods
such as washing machines, dishwasher, etc.
Figure 1. AS1105 - Typical Application Circuit
+5V
9.53k
ISET
MOSI
µP I/O
SCK
DIN
LOAD
CLK
GND
SEG A-G
SEP DP
GND
8 Segments
VDD
DIFG0-DIG3
4 Digits
AS1105
4-Digit µP Display
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Revision 1.36
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AS1105
Datasheet - P i n A s s i g n m e n t s
4 Pin Assignments
Figure 2. Pin Configuration (Top View)
DOUT
DIN
DIG0
GND
DIG2
DIG3
GND
DIG1
LOAD
CLK
1
2
3
4
5
6
7
8
9
10
SO
20
19
18
17
16
15
14
13
12
11
SEG D
SEG DP
SEG E
SEG C
VDD
I
SET
SEG G
SEG B
SEG F
SEG A
AS1105
4.1 Pin Descriptions
Table 1. Pin Descriptions
Pin Number
1
2
3,8,5,6
4,7
9
10
11:14, 17:20
15
16
Pin Name
DOUT
DIN
DIG0 : DIG3
GND
LOAD
CLK
SEGA:G, DP
ISET
VDD
Description
Serial data output for cascading drivers.
The output is valid after 16.5 clock cycles. The output is
never set to high impedance.
Data input.
Data is programmed into the 16-bit shift register on the rising CLK edge.
4-digit driver lines that sink the current from the common cathode of the display. In shutdown mode
the AS1105 switches the outputs to V
DD
.
Both GND pins must be connected.
Strobe input.
With the rising edge of the LOAD signal the 16-bit of serial data is latched into the
register.
Clock input.
The interface is capable to support clock frequencies up to 10MHz. The serial data is
clocked into the internal shift register with the rising edge of the CLK signal. On the DOUT pin the
data is applied with the falling edge of CLK.
Seven segment driver lines including the decimal point.
When a segment is turned off the
output is connected to GND.
The current into I
SET
determines the peak current through the segments and therefore the
brightness.
Positive Supply Voltage
(+5V)
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Revision 1.36
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AS1105
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Table 2. Absolute Maximum Ratings
Parameter
VDD to GND
DIN, CLK, LOAD to GND
All Other pins to GND
Current
DIG0–DIG3 Sink Current
SEGA–G, DP Source Current
Continuous Power Dissipation (TA = +85°C)
Wide SO
Operating Temperature Range
Storage Temperature Range
-40
-65
941
+85
+150
mW
ºC
ºC
The reflow peak soldering temperature (body
temperature) is specified according IPC/JEDEC
J-STD-020D “Moisture/Reflow Sensitivity
Classification for non-hermetic Solid State
Surface Mount Devices”.
Represents a maximum floor life of 168h
Derate 11.8mW/ºC above +70ºC
500
100
mA
mA
Min
-0.3
-0.3
-0.3
Max
+6
+6
V
DD
+ 0.3
Units
V
V
V
Notes
Package body temperature
+260
ºC
Moisture Sensitivity Level
3
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Revision 1.36
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AS1105
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
DD
= 5V, R
SET
= 9.53kΩ±1%, T
A
= T
MIN
to T
MAX
, unless otherwise noted.
Table 3. Electrical Characteristics
Symbol
V
DD
I
DDSD
Parameter
Operating Supply Voltage
Shutdown Supply Current
All digital inputs at V
DD
or GND,
T
A
= +25ºC
R
SET
= open circuit
I
DD
f
OSC
I
DIGIT
I
SEG
ΔI
SEG
I
DIGIT
I
SEG
Logic Inputs
I
IH
, I
IL
V
IH
V
IL
V
OH
V
OL
Input Current DIN, CLK, LOAD
Logic High Input Voltage
Logic Low Input Voltage
Output High Voltage
Output Low Voltage
Hysteresis Voltage
Timing Characteristics
t
CP
t
CH
t
CL
t
CSH
t
DS
t
DH
t
DO
t
LDCK
t
CSW
t
DSPD
CLK Clock Period
CLK Pulse Width High
CLK Pulse Width Low
CLK Rise to LOAD Rise Hold Time
DIN Setup Time
DIN Hold Time
Output Data Propagation Delay
LOAD Rising Edge to Next Clock
Rising Edge
Minimum LOAD Pulse High
Data-to-Segment Delay
C
LOAD
= 50pF
50
50
2.25
100
50
50
0
25
0
25
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
DOUT, I
SOURCE
= -1mA
DOUT, I
SINK
= 1.6mA
DIN, CLK, LOAD
1
V
DD
- 1
0.4
V
IN
= 0V or V
DD
-1
3.5
0.8
1
µA
V
V
V
V
V
Operating Supply Current
Display Scan Rate
Digit Drive Sink Current
Segment Drive Source Current
Segment Drive Current Matching
Digit Drive Source Current
Segment Drive Sink Current
Digit off, V
DIGIT
= (V
DD
-0.3V)
Segment off, V
SEG
= 0.3V
-2
5
V
OUT
= 0.65V
T
A
= +25ºC, V
OUT
= (V
DD
-1V)
All segments and decimal point on,
I
SEG
= -40mA
500
320
-30
-40
3.0
-45
330
800
1300
Conditions
Min
4.0
Typ
5.0
20
Max
5.5
50
500
Units
V
µA
µA
mA
Hz
mA
mA
%
mA
mA
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Revision 1.36
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