Register Settings - Analog Devices AFDF7021 Application Note

AN-1258

REGISTER SETTINGS

Table 1 gives an overview of the primary registers adjusted during the calibration process. Recommended values are provided in the Notes
column of this table. The parameters are also displayed in Figure 3.
Table 1. Register Settings
Setting
Tx/Rx
IR_CAL_SOURCE ÷ 2
IR_CAL_SOURCE_DRIVE_LEVEL
IR_GAIN_ADJUST_UP/DN
IR_GAIN_ADJUST_I/Q
IR_GAIN_ADJUST_MAG
IR_PHASE_ADJUST_DIRECTION
IR_PHASE_ADJUST_MAG
IF_CAL_COARSE
AGC_MODE
LNA_GAIN
FILTER_GAIN
LNA_CURRENT (BIAS)
DEMOD_CLK_DIVIDE
IF_BW
Register Notes
R0_DB27 This sets the device in Tx or Rx mode. The required setting is Receive (Decimal 1).
R6_DB30 This affects the power of the internal tone. The recommended setting is On
(Decimal 1).
R6_DB[28:29] This affects the power of the internal tone. The recommended setting is High
(Decimal 3).
R5_DB31 This determines whether the level applied is a gain or attenuation. It is
recommended to use only Attenuate (Decimal 1).
R5_DB30 This sets whether the gain adjust is applied to either the I Channel (Decimal 0) or
Q Channel (Decimal 1).
R5_DB[25:29] In attenuate mode, only 4 gain adjust level bits (Settings 0 to 15) are used. In
gain mode, all 5 bits (Settings 0 to 31) can be used. However, the results wrap
around with 5 bits and, thus,this is not recommended.
R5_DB24 This sets whether the phase adjust is applied to either the I Channel (Decimal 0)
or Q Channel (Decimal 1).
R5_DB[20:23] This sets the level of phase adjust.
R5_DB4 This sets to Do Cal (Decimal 1). Fine calibration is not necessary.
R9_DB[18:19] This sets to Manual (Decimal 1) during calibration.
R9_DB[20:21] The optimum setting with external tone depends on the power of the tone
applied. The recommended setting when using the internal tone is Low
(Decimal 0). This ensures that the impact of external noise at the image
frequency picked up at the antenna is minimized. Although the tone is injected
after the LNA, this setting still affects the power of the internal tone. The LNA
gain should only be increased as a last resort when trying to increase the power
of the internal tone.
R9_DB[22:23] This affects the power of the internal and external tone. The optimum setting
depends on the power of the external tone applied or the configuration of the
internal source power level.
R9_DB[26:27] The default value for this is Default (Decimal 0). In cases where the internal tone
is used, this should be increased to High (Decimal 3). This provides isolation
from any noise present on the RFIN pins which could distort the calibration.
R3_DB[6:9] Sets the DEMOD_CLK, that is, the fundamental frequency of the internal tone.
Setting this to the minimum value possible results in a stronger tone.
Depending on the value of XTAL, it may be necessary to increase this value to
generate a tone near the frequency of operation.
R4_DB[30:31] Set this to the Widest Setting (Decimal 2).
Rev. 0 | Page 4 of 12
Application Note