AK2346A Datasheet, PDF (35/37 Pages) Asahi Kasei Microsystems – Two-way Radio Audio Processor

ASAHI KASEI
[AK2346A]
6) Clock Generation
The clock source can be chosen from either built-in crystal oscillator circuit or externally supplied.
When the built-in oscillator circuit is used, connect a 14.7456MHz crystal oscillator, a resistor,
and capacitors as shown in Fig. 1. AK2346A is designed to get a stable oscillation for the
electrical equivalent circuitry of quartz crystal unit: resonance resistance≤80Ω(Max.) and shunt
capacitance≤1.5pF(Max.). It is recommended that external 12pF capacitors should be connected
so that the total load capacitance does not exceed the load capacitance≤6pF (1.5pF+12pF//12pF)
or less. These external components are mounted as close to the device pins as possible.
When a clock signal is supplied externally, not only 3.6864MHz but also 7.3728MHz (twice higher
than 3.6864MHz), 11.0592MHz (three times higher than 3.6864MHz), and 14.7456MHz (four
times higher than 3.6864MHz) are supported. However, the internal frequency must always be
set to 3.6864MHz by selecting division by 2, 3, or 4 for the divider in the subsequent stage.
Connect the clock signal as shown in Fig. 2 or Fig. 3 according to the clock amplitude level.
The circuit in the first stage of the XIN pin has a constant threshold voltage (0.8V). Therefore, if
the high level of the input clock is 1.5V or higher and the low level is 0.5V or lower, connect the
clock signal as shown in Fig. 2. If the input clock amplitude (p-p value) is between 0.2V and 1.0V,
connect the clock signal as shown in Fig. 3.
When the clock is to be shared with peripheral ICs, the clock must be input and output on the XIN
pin. The clock amplitude must not exceed the absolute maximum rating.
XIN
12pF
1MΩ
XOUT
LSI
Fig. 1
14.7456MHz
12pF
External Clock IN
6
XIN
3.6864MHz
7.3728MHz
5
11.0592MHz
LSI
14.7456MHz
Fig. 2
XIN
0.01uF
XOUT
LSI
Fig. 3
External Clock IN
3.6864MHz
7.3728MHz
11.0592MHz
14.7456MHz
MS1289-E-02
- 35 -
2012/06