Silan
Semiconductors
2. VOLUME UP, DOWN CONTROL CIRCUIT
Volume up, down control is executed by UP , DN key input.
* The 1 step / 1 push volume is controlled by "L" level of UP , DN key.
* If UP , DN key is input "L" continuously, volume level is changed continuously.
* Timing of key input
UP / DN INPUT
VOLUME LEVEL
t
T
a
(fOSC=20Hz)
Note: t : Prevent time for chattering 2.2h1/fosc(110ms)
T: Switching time to automatic mode 10h1/fosc(500ms)
a : Up,Down speed 2h1/fosc(100ms)
foscCx•Rx(Hz) : Rx=12~220k¡
SC9235
3. DC OUTPUT CIRCUIT FOR VOLUME LEVEL
DC output for volume level meter is internally connected to D−A converter (R/2R type).
8 stage output voltage which is corresponded to volume level is generated.
Because output impedance ≈ 22kΩ (typ.) is high, If input impedance of next setting level meter IC is low,
set to Buffer.
Equivalence circuit
2R
DC-OUT
R
2R
2R R
R
R≈22kΩ
* Volume step and Output voltage
Step Attenuation(dB) Output Voltage(V)
0~3
0~6
7/ 8 VDD
4~7
8 ~ 14
6/ 8 VDD
8 ~ 11
16 ~ 22
5/ 8 VDD
12 ~ 15
24 ~ 30
4/ 8 VDD
16 ~ 19
32 ~ 38
3/ 8 VDD
20 ~ 23
40 ~ 50
2/ 8 VDD
24 ~ 27
54 ~ 66
1/ 8 VDD
28 ~ 31
70 ~ ∞
0
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2000.12.31
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