参数资料
型号: TS4974IQT
厂商: STMICROELECTRONICS
元件分类: 音频控制
英文描述: 1 CHANNEL(S), VOLUME CONTROL CIRCUIT, DSO10
封装: 3 X 3 MM, 0.50 MM PITCH, ROHS COMPLIANT, DFN-10
文件页数: 14/25页
文件大小: 319K
代理商: TS4974IQT
TS4974
Application information
21/25
The volume is controlled by means of two pins, UP/DVC and DOWN/DVC. When the VIL
voltage is applied, it activates the increase or decrease in gain. When one of the input pins
is grounded, volume changing is activated. When both volume UP and DOWN functions are
activated at the same time, there is no effect on the volume.
The UP/DVC and DOWN/DVC inputs need to be pulled-up or pulled-down, so a pair of
external pull-up or pull-down resistors are required. When pull-up resistors are used, it is
dependent on the application which values of resistors you should choose in the range from
10k
Ω to 1MΩ. The current flowing through the switch S1 or S2 during volume changing is
adjusted by the value of the pull-up resistors.
When pull-down resistors are used, the values are chosen in the range from at least 430k
Ω
to 1M
Ω (a value 470kΩ is recommended). Typically, in this case a 10A current flows through
the switch S1 or S2 during volume changing.
Table 2 on page 3 indicates the values of the VU/D voltages required to activate an increase
or decrease in volume. The volume can also be controlled by a microcontroller. In this case,
transistors can be used as switches for grounding the UP/DVC and DOWN/DVC pins.
The TS4974 integrates a debouncing system which does not take into account UP or
DOWN pulses that are shorter than the tdebounce time. In addition, an autorepeat function is
implemented. When a continuous voltage is applied to the UP or DOWN pin, the gain is
continuously increased or decreased after a certain time called tautorepeat. The first period of
each autorepeat sequence is longer (tautorepeat x 1.5) to avoid any parasitic activation. In this
mode, the time trange is necessary to cover the whole gain range of the device.
Figure 42 explains the meaning of the debounce, autorepeat and range times (respectively
tdebounce, tautorepeat and trange). It shows how the volume increases over the whole volume
range from the minimum gain -33 dB to the maximum gain +12 dB by 3 dB steps.
Figure 42.
Example of volume change
V
UP
G=+12dB
G=-33dB
Gain
(dB)
t
debounce
t
range
1.5 x t
autorepeat
Time
G=3dB
t
autorepeat
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