CXA1898Q
(2) AMS level setting
The AMS level is set by adjusting HPF gain and cut-off frequency with the external resistor and capacitor at
Pin 48.
G and fc in Fig. 2 are obtained from the following formula.
G = 20log (1 + 100k/R) [dB] – (1)
fc = 1/ (2 • π • C • R)
[Hz]
Full-wave rectifier is applied for the signal at DET.
Signal detection time is set by the time constant of Pin 1 external resistor and capacitor.
DET signal detection level:
= –7.5dBm (typ.)
= playback equalizer reference output level + AMS level + HPF gain – (2)
Playback equalizer reference output level of –21dBm is 0dB.
Ex.)
To set AMS level at –25dB, determine and set the constant for Pin 48 external resistor.
(Calculate assuming PBOUT1 = PBOUT2)
First, get the required HPF gain from formula (2).
–7.5dBm = –21dBm + (–25dB) + HPF gain,
so HPF gain = 38.5dB.
Next, get Pin 48 external resistance from formula (1).
38.5dB = 20log (1 + 100k/R),
so R ≈ 1.2kΩ,
and external resistance is 1.2kΩ.
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