AK2401 Datasheet, PDF (63/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
* G_N takes a processing result of the AGC circuit when AGCOFF bit=”0”, and it takes setting value of
PGAGAIN_I[5:0] bits <Address0x15> when AGCOFF bit = “1”. In this document, “G_N” indicates gain
value that unit is [dB]. Note that it does not indicating register values. A saturation process will be
executed when G_CORR result is greater than 28 dB (Maximum PGA Gain) to 28dB and a saturation
process will be executed when G_CORR result is less than -20 dB (Minimum PGA Gain) to -20dB.
LNA gain mode switching conditions are shown below.
 Normal Gain Mode to Low Gain Mode
 When G_CORR becomes smaller than the threshold value set by LNA_TGT_L[5:0] bits.
 When PGA gain becomes the minimum value (-20dB).
(There is a case that G_CORR will not become less than a threshold set by LNA_TGT_L bits if a
convergence target level (AGCTGT bits) is set under -2dBm. This condition is for such a case.)
 Low Gain Mode to Normal Gain Mode
 When G_CORR becomes greater than the value set by LNA_TGT_H[5:0] bits.
LNA gain mode can be read by R_LNA_LGMODE bit <Address0x2F>. The LNA is in normal gain mode
when R_LNA_LGMODE bit is “0”. It is in low gain mode when R_LNA_LGMODE bit is “1”.
When LNA_AGCOFF bit = “0”, AGC process result can be read by this bit. When LNA_AGCOFFbit = “1”,
LNA_LGMODE bits setting is readout.
If AGCOFF bit = “1” and LNA_AGCOFF bit = “0”, PGA gain can be set manually and LNA gain mode is
changed according to the PGA gain. Threshold calculations of PGA and AGC are the same. PGA can be
set I channel and Q channel gain independently but I channel gain setting is used for both channels in
LNA. LNA gain mode can be set manually by LNA_LGMODE bit when LNA_LGMODE bit = “1”.
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