AK1547 Datasheet, PDF (24/37 Pages) Asahi Kasei Microsystems – 4GHz Low Noise Integer-N Frequency Synthesizer

[AK1547]
CP2[2:0] : Charge pump current setting 2
CP1[2:0] : Charge pump current setting 1
AK1547 provides two setting for charge pump current. They can be set by {CP1} and {CP2}.
The following formula shows the relationship among the resistance value, the register setting and the
electric current.
Charge pump minimum current (Icp_min)[A] = 17.46 / Resistance connected to the BIAS pin [Ω]
Charge pump current (Icp) [A] = Icp_min [A] × ({CP1} or {CP2} setting +1)
The following table shows the typical Icp for each status.
D18 D17 D16
D15 D14 D13
000
001
010
011
100
101
110
111
Icp (typical)
Bias Resistance
33 kΩ
27 kΩ
22 kΩ
529
647
794
1058
1293
1587
1587
1940
2381
2116
2587
3175
262.7
3233
3968
3175
3880
4762
3704
4527
5555
4233
5173
6349
[Unit : μA]
Remarks
TIMER[3:0] : Sets the switchover time for CP2-to-CP1
This is enabled when {FAST[1:0]} is ”11Bin” and {[CPGAIN}=”1”.
The charge pump current is set into value {CP2[2:0]} designate during switchover time. It goes to be
{CP1[2:0]} setting value after the time out.
The following formula shows the relationship between the switchover time and the counter value.
Switchover time = 1 / F_PFD × Counter Value
Counter Value = 3 + Timer[3:0] × 4
MS1464-E-00
24
2012/9