SILAN SC8521 Datasheet

Silan
Semiconductors

SC8521

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 (

DR0toDR6

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.

) and eight sense lines (SN0

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

SOP-20

SC8521

Package

PIN CONFIGURATIONS

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

XTAL1

XTAL2

SN7

SN0

SN1

SN2

SN3

SN6

SN4

SN5

1

2

3

4

5

6

7

8

9

10

20

VDD

19

Lout

18

VSS

DR6

17

16

DR0

15

DR1

SC8521

14

DR2

13

DR3

12

DR4

11

DR5

REV: 1.3 2002.03.01

1

Silan
Semiconductors

BLOCK DIAGRAM

XTAL1 XTAL2

SC8521

432kHZ

1 2

SN0
SN1
SN2
SN3
SN4
SN5
SN6
SN7
DR0
DR1
DR2
DR3
DR4
DR5
DR6

4
5
6
7
9

10

8

3
16
15
14
13
12
11
17

OSCILLATOR

KEY SCANNING

TIMING GENERATOR AND CONTROL

1K x 8 ROM

PULSE GENERATOR

SHIFT REGISTER

20 18

V

DD

V

SS

19

Lout

OUTPUT DRIVER

ABSOLUTE MAXIMUM RATING

Characteristic Symbol Value Unit

Supply Voltage V
PowerDissipation P
Thermal Derating
Storage Temperature T
Operating Temperature T

DD

D

K∂

STG
OPR

5V
25 mW
10

-65 ~ +150

-20 ~ +80

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.3 2002.03.01

2

mW/°C

°C
°C

Silan
Semiconductors

SC8521

ELECTRICAL CHARACTERISTICS

(Tamb=25°C, unless otherwise specified)

Symbol Parameter Test condition Min Type Max Unit

Operating supply voltage V
Supply current I
Quiescent current IDD(q)
Operating ambient temperature T

Sense lines (input only and will have a weak internal pull-up resistance)

LOW level input voltage V
HIGH level input voltage V
Pull-up resistance Rpu VDD=3V 50 -- 100

Driver lines (output only; open drain; maximum on-resistance when LOW)

Maximum on-resistance Ron VDD=3V -- -- 2

Output drive (has a weak pull-up resistance)

Source current Isink VDD=3V; VO=1.5V 3.5 4.5 5.5 mA

DD

DD

VDD=3V; TA=25°C
V

=3V; TA=25°C

DD

A

IL
IH

2.2 -- 4.5 V

-- -- 2 mA

-- -- 1

-10 -- +50

-- -- 0.3V

0.7V

DD

-- -- V

DD

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

12
13
14
15
16

DR5

DR4
DR3
DR2

DR1

DR0

Drive line 5 for key matrix (active LOW)
Drive line 4 for key matrix (active LOW)

Drive line 3 for key matrix (active LOW)
Drive line 2 for key matrix (active LOW)
Drive line 1 for key matrix (active LOW)

Drive line 0 for key matrix (active LOW)

µA
°C

V

KΩ

KΩ



To be continued

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.3 2002.03.01

3



Silan
Semiconductors

(Continued)

Pin No. Symbol Description

17
18 VSS Ground

19 Lout Output signal
20 VDD Power supply

DR6

FUNCTION DESCRIPTION

1. Key numbering for matrix is gi ven in tables 1

Table1 key numbering for 20-pin package

Driver lines

DR5

DR4
DR3
DR2

DR1
DR0
DR6

SN0 SN7 SN1 SN2 SN3 SN6 SN4 SN5

0:BANK0 1 2 3 4 5 6 7

8:BANK19 101112131415
16:BANK2 17 18 19 20 21 22 23
24:BANK3 25 26 27 28 29 30 31
32:BANK4 33 34 35 36 37 38 39
40:BANK5 41 42 43 44 45 46 47
48:BANK6 49 50 51 52 53 54 55

SN0 connected GND, send BANK7 code. BANK0----7 see the following code table.

Drive line 6 for key matrix (active LOW)

Sense lines

SC8521

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

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.3 2002.03.01

4

Silan
Semiconductors

generated code temporarily (select different bank) to obtain multi-function keys. With this option the jumper wires

SC8521

or switch must be connected between sense line SN0 and one of the drivelines

DR0toDR6

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.

no key

end control

start input

STOP

Q

CLK1

432 kHz INV

CLK2

CONTROL

DIVIDE-BY-4096

432kHz

OSCILLATOR DIVIDE BY 12

SQ

CLK

R

CLR

Timer schematic diagram

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

5

pulse

C0

TIMER

C11

REV: 1.3 2002.03.01