AK2401 Datasheet, PDF (55/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
13.8.5. Fast Track Mode
Fast track mode of HPF is enabled by setting HPF_FAST bit to “1” <Address 0x24>. The cutoff frequency
of the high-pass filter is temporary raised for a quick convergence of DC offset change that occurs when
the PGA gain is changed during AGC operation or when power-down is released.
Set the register in <Address 0x25> for Fast Track mode settings.
FAST_GAIN[1:0]: PGA gain change amount that is the trigger of cutoff frequency change
HPF_FTIM[2:0]: Cutoff Frequency Changing Time
FAST_FC[1:0]: Cutoff Frequency after Switching (Table 7)
Table 5. Gain Change Amount
FAST_GAIN
[1]
[0]
Gain Change
Amount
Unit
0
0
1 (default)
0
1
1
0
4
dB
6
1
1
8
Table 6. Cutoff Frequency Changing Time
HPF_FTIM
[2] [1] [0]
Switching Time
Unit
0
0
0
30 (default)
0
0
1
60
0
1
0
120
0
1
1
1
0
0
240
480
µsec
1
0
1
960
1
1
0
1300
1
1
1
1600
FAST_FC
[2]
[1]
0
0
0
1
1
0
1
1
Table 7. Cutoff Frequency after Switching
Cutoff Frequency
TCXO=19.2MHz TCXO=18.432MHz Unit
Note
12714 (default) 12205 (default)
The same frequency as HPF_FC=11xx
6159
3031
5912
2910
The same frequency as HPF_FC=1011
Hz
The same frequency as HPF_FC=1010
1504
1444
The same frequency as HPF_FC=1001
017003093-E-00
55
2017/3