參數(shù)資料
型號: TC9488F
元件分類: 消費家電
英文描述: SPECIALTY CONSUMER CIRCUIT, PDSO30
封裝: 0.375 INCH, 1 MM PITCH, PLASTIC, SSOP-30
文件頁數(shù): 9/14頁
文件大小: 313K
代理商: TC9488F
TC9455,88F/N
2002-02-05
4
Operation
1.
Oscillator circuit
The TC9455F/N and TC9488F/N generate an internal system clock using the CR oscillator circuit.
Connecting a capacitance (C) of 68 pF and a resistance (R) of 5.6 k sets the oscillator frequency to approx.
4 MHz and the sampling frequency to 32 kHz.
Varying the external capacitance enables the oscillator frequency and sampling frequency for the system
clock to be adjusted. Varying the system clock enables the delay time to be adjusted.
Figure 1 shows the CR oscillator circuit.
1.1
How to determine oscillator frequency (f)
f [MHz] = 1532/(C [pF] × R [k])
= 1532/(68 × 5.6)
≈ 4.0 MHz (Note 2)
Note 2: The oscillator frequency is a typical value (Ta =
25°C). Set the resistance to between 4.7 k and
6.8 k.
1.2
How to determine sampling frequency (fs)
fs [kHz] = f/128
= 4.0/128
≈ 32 kHz
2.
Microphone amps
The IC incorporates microphone amps with auto level control (ALC).
The microphone amp gain is typically 36dB.
When a signal from 0 to 46dB is input, the ALC circuit can control the output signal level.
Changing the external capacitor connected to the ALC circuit to a resistor sets the ALC circuit to off.
Figure 2 shows the microphone amp circuit.
When C = 4.7 F, the attack and release times are as follows:
Attack time = Approx. 29 ms
Release time = Approx. 1.6 s
Setting the capacitance (C) to a smaller value enables the
attack and release times to be adjusted. When the ALC circuit
is not used, change the capacitor (*1) to a resistor (approx. 10
k), and connect to GND line.
At power on, while the capacitor is being charged, no sound is
output. So, use a capacitance of 4.7 F or less.
Figure 1
CR Oscillator circuit
Figure 2
Microphone amp with ALC
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