FAQ - IF Rx with Narrowband Filters

AK2365A

IF Rx with Narrowband Filters

[Q0445]
・Can local frequencies other than 45.9MHz, 50.4MHz, and 57.6MHz be used?
A.
・No, they can not.  The frequency not specified can not be used because the local frequency is also used for an operating clock in the IC. Each of three frequencies is the frequency generated by multiplying the popular TCXO frequency 15.3MHz, 16.8MHz and 19.2MHz by three.
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[Q0446]
・In the data sheet, is the hardware reset described in the power-up sequence replaceable by software reset?
A.
・No, it is not. The hardware reset must be executed for reset operation at power-up.
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[Q0447]
・It is stated in the datasheet that "set the digital input pin to RSTN pin to High, SCLK pin to Low, SDATA pin to Low and CSN pin to Low" when hardware reset is performed. What does this mean?
A.
・It is recommended to fix the inputs of the SCLK, SDATA and CSN pins during the reset operation and when reset is released in order to reset confirmly. Each control pin is not pulled-up or pulled-down in the AK2365A. The described polarity is an example and is not restricted.
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[Q0448]
・How can I control intermittent operation while keeping the calibration value?
A.
・The Mode2 is assumed to be used.
If the intermitted operation is executed by the PDN pin, the hardware reset and calibration must be executed each time.
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[Q0449]
・In the mass production process, there are not many proportions, but there are some samples where the demodulated output level sticks to the supply voltage or ground. Why?
A.
・If the hardware reset or calibration is not executed normally, such a phenomenon may be caused. Because the demodulated output level is calibrated by the calibration executed by register setting.
The LO signal must be supplied stably when the calibration is executed. And it takes 500us until the internal bias becomes stable after setting Mode6 by register when the capacitance connected to LOIN pin is recommended 100pF. If the capacitance connected to LOIN pin is larger than recommended value, the bias stable time becomes longer.
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[Q0450]
・Should the operation modes for calibration be Mode6? If LOBUF, VIREF, Discriminator needs to be powered up, is  Mode7 acceptable?
A.
・The Mode7 is acceptable.
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[Q0451]
・With respect to the noise squelch circuit, the output from the NRECTO pin is large and DETO can not detect "L". How is it solved.
A.
・Insert such as a resistor attenuator at the input of the noise amplifier and adjust the amount of the noise to draw desired NRECTO output curve. The circuit constants in the data sheet are set to increase the gain for the noise input because of the shipping test.
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[Q0452]
・What is the input impedance of IFIP pin?
A.
・The input impedance depends on an external resistor connected to the ground, because the input of the IFIP is Hi-Z. The recommended value of this resistor is 750Ω. Adding a inductor and capacitor to match to 50Ω, the electrical characteristics are measured.
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