AK1599V Datasheet, PDF (18/41 Pages) Asahi Kasei Microsystems – RF Transmitter for Satellite Communication

[AK1599V]
9.5. Fast lock up mode
The fast lock up mode becomes effective by setting FASTEN bit of address 0x04 = ”1”.
○Fast lock up mode
After setting Address0x01 when FASTEN bit = “1”, Fast Lock Up mode starts after VCO calibration. The
Fast Lock Up mode is enabled only when the time period set by the timer according to the counter value
defined by FAST [3:0] bits in Address0x04. The charge pump current is set to the value specified by CP2
bit. After the specified time period elapses, the Fast Lock Up mode is finished and switched to the
normal operation, and the charge pump current returns to CP1 bit setting.
Operation mode
Normal
Calibration
Fast Lock Up time
specified by the timer
Fast Lock Up
Normal
Charge pump current
CP1
Hi-Z
CP2
CP1
Frequency setting (Setting Address0x01)
Fig.9 Fast Lock up Mode Timing Chart
○Timer period
FAST[3:0] bits in Address0x04 is used to set the time period for the fast lock mode. The following
formula is used to calculate the time period
Time period = (511 + FAST[3:0] × 512) / PFD frequency
9.6. VCO
<Calibration>
The calibration starts by setting Address0x01 when MODE[1:0] bits in Address 0x04 = “00” or “01” and
PDN pin = ”H”. During the calibration, VCO VTUNE is disconnected from the output of the loop filter and
connected to an internal reference voltage. In addition, the charge pump output is disabled during
calibration.
The internal reference voltage must be stable so that the calibration is done correctly. Therefore, after
setting PDN pin = “H”, it is necessary to wait 500s at least before setting Address0x01.
CALTM[3:0] bits determines the calibration time. The larger CALTM[3:0] bits are set, the higher
calibration precision becomes, but the calibration time becomes long. The value calculated by the
following formula is recommended to achieve enough calibration precision. However, CALTM[3:0] bits
should be set between 1 and 11. 0 and over 12 are prohibited.
CALTM[3:0] ≥ log2 (PFD frequency / 20000)
The calibration time can be estimated as following calculation.
Calibration time = 1 / PFD frequency × {(6 + 2 ^ {CALTM [3:0]}) × 8 + 3}
015006835-E-00
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2015/5