AK1572 Datasheet, PDF (25/35 Pages) Asahi Kasei Microsystems – Down Converter Mixer with Fractional-N Frequency Synthesizer and VCO

[AK1572]
13. Frequency Setup
The following formula is used to calculate the frequency setting for the AK1572.
Frequency setting ＝Ref Frequency × (INT+FRAC/MOD)
Ref Frequency ：PFD fequency
INT
：Integer divide Number (Refer to <Address 0x01>：INT[11:0])
FRAC
：Numenator setting number (Refer to <Address 0x02>：FRAC[11:0])
MOD
：Denominator setting number (Refer to <Address 0x03>：MOD[11:0])
Set in the range of 35 to 4091 for INT[11:0].
Set in the range of 0 to (MOD-1) for FRAC[11:0]
Set in the range of 2 to 4095 for MOD[11:0]
○ Example
To complete Ref Frequency=19.2MHz, Frequency setting=2460.1MHz, set as follows
INT =
128
FRAC =
25
MOD =
192
Frequency setting = 19.2MHz × (128 + (25 / 192)) = 2460.1MHz
By writing <Address 0x01, 0x02, 0x03>, frequency is set. When <Address 0x01> is written, the
setting of <Address 0x03> and <Addresses 0x02> is reflected in the internal circuit. At the time of the
writing of <Address 0x01>, it is necessary for a synthesizer block to be powered on. The writing of
<Address 0x01> as a trigger, frequency setting and VCO calibration are carried out, and fast lock
counter starts operation. To set frequency definitely, <Address 0x01> should be written in the state
that {MODE [1:0]} in <Address 0x04> is 0 or 1 or 2 and [PDN] pin is “H”.
MS1551-E-00
25
2013/8