Silan
Semiconductors
SC8521
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.3
2002.03.01
1
INFRARED REMOTE CONTROL
TRANSMITTER RC5
DESCRIPTION
The
SC8521 can
be
used
in
infrared
remote control
transmitters. It generates output pulses, in accordance with the RC5
protocol, when a key is pressed. The IC does not contain a software
programmable processor. However, it does contain a ROM in which
the codes that have to be transmitted are stored. The oscillator
frequency may be optionally chosen as 432KHz. For 432KHz
additional external capacitors must be connected. When a key in the
key-matrix is pressed a driveline will be connected to a sense line.
This causes the oscillator to start and a corresponding code will be
generated conforming to the RC5 protocol.
Seven drive lines ( DR0 to DR6 ) and eight sense lines (SN0
to SN7) may be connected via the key matrix to scan the keys.
When two or more keys are activated simultaneously no
transmission will take place.
FEATURES
RC5 protocol
Maximum of 56 keys (20-pin version)
Option of multi-system or single system transmitter
-- Multi-system: maximum 8 system, selection by key
-- Single system: maximum 8 different systems per IC, selection
by jumper wire or switch.
SOP-20
Power-down and key wake-up
High output current (
45mA)
Oscillator frequency of 432KHz
Multiple key protection
Option of 25% or 33% duty factor
ORDERING INFORMATION
SC8521
SOP-20
Package
PIN CONFIGURATIONS
1
2
3
4
5
6
7
8
16
15
14
13
12
11
9
10
20
19
18
17
SC
85
21
XTAL1
XTAL2
SN0
SN1
SN2
SN3
SN4
SN5
VDD
Lout
VSS
DR0
DR1
DR2
DR3
DR4
SN6
SN7
DR6
DR5
Silan
Semiconductors
SC8521
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.3
2002.03.01
2
BLOCK DIAGRAM
OSCILLATOR
KEY SCANNING
4
5
6
7
9
10
8
3
16
15
14
13
12
11
17
TIMING GENERATOR AND CONTROL
1K
x
8
R
O
M
P
U
L
S
E
G
EN
ER
A
T
O
R
OU
T
P
UT
DRIV
E
R
SHIFT REGISTER
1
2
19
20
18
SN0
SN1
SN2
SN3
SN4
SN5
SN6
SN7
DR0
DR1
DR2
DR3
DR4
DR5
DR6
V
DD
V
SS
Lout
XTAL1
XTAL2
432kHZ
ABSOLUTE MAXIMUM RATING
Characteristic Symbol
Value
Unit
Supply Voltage
V
DD
5
V
Power Dissipation
P
D
25
mW
Thermal Derating
K
10
mW/
C
Storage Temperature
T
STG
-65 ~ +150
C
Operating Temperature
T
OPR
-20 ~ +80
C
Silan
Semiconductors
SC8521
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.3
2002.03.01
3
ELECTRICAL CHARACTERISTICS
(Tamb=25
C,
unless otherwise specified)
Symbol Parameter
Test
condition
Min
Type
Max
Unit
Operating supply voltage
V
DD
2.2
--
4.5
V
Supply current
I
DD
V
DD
=3V; TA=25
C
--
--
2
mA
Quiescent current
I
DD
(q)
V
DD
=3V; TA=25
C
--
--
1
A
Operating ambient temperature
T
A
-10
--
+50
C
Sense lines (input only and will have a weak internal pull-up resistance)
LOW level input voltage
V
IL
--
--
0.3V
DD
V
HIGH level input voltage
V
IH
0.7V
DD
--
--
V
Pull-up resistance
Rpu
V
DD
=3V
50
--
100
K
Driver lines (output only; open drain; maximum on-resistance when LOW)
Maximum on-resistance
Ron
V
DD
=3V
--
--
2
K
Output drive (has a weak pull-up resistance)
Source current
Isink
V
DD
=3V; VO=1.5V
3.5
4.5
5.5
mA
PIN DESCRIPTION
20-pin dual in-line and small outline package (SO-20)
Pin No.
Symbol
Description
1
XTAL1
Oscillator input
2
XTAL2
Oscillator output
3
SN7
Sense line 7 for key matrix
4
SN0
Sense line 0 for key matrix
5
SN1
Sense line 1 for key matrix
6
SN2
Sense line 2 for key matrix
7
SN3
Sense line 3 for key matrix
8
SN6
Sense line 6 for matrix
9
SN4
Sense line 4 for matrix
10
SN5
Sense line 5 for matrix
11
DR5
Drive line 5 for key matrix (active LOW)
12
DR4
Drive line 4 for key matrix (active LOW)
13
DR3
Drive line 3 for key matrix (active LOW)
14
DR2
Drive line 2 for key matrix (active LOW)
15
DR1
Drive line 1 for key matrix (active LOW)
16
DR0
Drive line 0 for key matrix (active LOW)
To be continued
Silan
Semiconductors
SC8521
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.3
2002.03.01
4
(Continued)
Pin No.
Symbol
Description
17
DR6
Drive line 6 for key matrix (active LOW)
18
V
SS
Ground
19
Lout
Output signal
20
V
DD
Power supply
FUNCTION DESCRIPTION
1. Key numbering for matrix is given in tables 1
Table1
key numbering for 20-pin package
Sense lines
Driver lines
SN0 SN7 SN1 SN2 SN3 SN6 SN4 SN5
DR5
0:BANK0
1
2
3
4
5
6
7
DR4
8:BANK1
9
10
11
12
13
14
15
DR3
16:BANK2
17
18
19
20
21
22
23
DR2
24:BANK3
25
26
27
28
29
30
31
DR1
32:BANK4
33
34
35
36
37
38
39
DR0
40:BANK5
41
42
43
44
45
46
47
DR6
48:BANK6
49
50
51
52
53
54
55
SN0 connected GND, send BANK7 code. BANK0----7 see the following code table.
When the keys have been scanned the key-number of the activated key serves as the address of the ROM to
obtain the required codeword. Consequently, key numbers 6, 7, 14, 15, 22, 23, 30, 31, 38, 39 and 40 to 55 will not
be addressed.
The ROM contains 8 banks of 64 code words. Thus for each key a maximum of 8 different code words may be
generated. With multi-system use, 8 different systems (e.g. TV, VCR, tuner, CD etc.) may be selected. Apart from
the system bits the command bits may also be different in different banks (true multi-function keys). Selection can
be performed using the keys. For each key three bank selected bits are present that determine which bank will be
selected for the next key.
For each key an `inhibit' bit is also present. When this bit is at logic 1 at an address in a given bank, and when
the corresponding key is pressed (when this bank has been selected) no transmission will take place.
A single system option is available however, whereby instead of keys jumper wire and/or a switch may be used
for bank selection. Using this option it is possible to program different transmitter models in one IC and select the
required bank by means of jumper wire. Instead of a jumper wire a side-switch may also be used to change the
Silan
Semiconductors
SC8521
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
REV: 1.3
2002.03.01
5
generated code temporarily (select different bank) to obtain multi-function keys. With this option the jumper wires
or switch must be connected between sense line SN0 and one of the drivelines DR0 to DR6 or ground. This
means that SN0 cannot be used to connect keys and the maximum number of keys will be 49 keys for a 20-pin
package.
It is not possible to use a combination of jumper wires and selection keys for bank selection in one unit. The
output of the ROM is loaded into a shift register that provides the input bits for the pulse generator. This pulse
generator drives the output pin.
2. Timing generator
A schematic diagram of the timing generator is illustrated the oscillator frequency is 432KHz. The timing
generator is stopped when no key is activated and started again when a key is pressed.
The output of the oscillator (CLK1) is divided by 12 for 432KHz. Selection is achieved using a mask option. The
output of the divider is CLK2 which is used for clocking of the control timer. The frequency of CLK2 is 36 KHz and
the inverse is used to generate the output pulses in the subcarrier frequency. By mask option the duty factor can
be chosen to be 25% or 33%.
The control timer has a length of 4096 subcarrier (pulse) periods. This is equal to the transmission repletion time.
A bit time is equal to 64 pulses and the repetition time is 64 bit times. The control timer provides the timing of the
key scanning, the ROM access and the code transmission. When the control timer has arrived at a certain state
and no key has been pressed for at least 28 ms, a stop signal will be generated which will stop the oscillator. All
drivelines will then be set to logic 0. As soon as a key is pressed one of the sense lines will become logic 0. This
will generate a start signal, which will restart the oscillator.
OSCILLATOR
DIVIDE BY 12
CONTROL
TIMER
DIVIDE-BY-4096
C0
C11
pulse
R
S
Q
Q
CLR
432kHz
no key
end control
start input
STOP
CLK1
432 kHz
INV
CLK
CLK2
Timer schematic diagram
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