Gain Control Modes - Analog Devices ADRV9005 Reference Manual

Reference Manual
RECEIVER GAIN CONTROL
Table 74. Sample Rows from a Modified Rx Gain Table
Gain Table Total Effective ADRV9002
1
Index Attenuation (dB)
238 34
239 32
240 30
... ...
253 4
254 2
255 0
1
This column is not part of the Rx Gain Table and included only for illustrative purposes.
Notice that no new rows needed to be created. Rows which represented the more granular step changes were simply removed.

GAIN CONTROL MODES

Select the gain control mode through the API function adi_adrv9001_Rx_GainControl_Mode_Set() for a specified channel. For more details,
refer to the API Doxygen document. adi_adrv9001_RxGainControlMode_e is an enum to select the gain mode.
options.
Table 75. Definition of adi_adrv9001_RxGainControlMode_e
ENUM
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_SPI
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_PIN
ADI_ADRV9001_RX_GAIN_CONTROL_MODE_AUTO
The adi_common_ChannelNumber_e enum indicates the receiver channel to use
Table 76. Definition of adi_common_ChannelNumber_e
ENUM
ADI_CHANNEL_1
ADI_CHANNEL_2
Automatic Gain Control (AGC)
In the AGC mode, a built-in state machine automatically controls the gain based on the user-defined configuration. The AGC is configured to
one of two modes:
Peak detect mode, where only the peak detectors are used to make gain changes.
►
Peak/Power detect mode, where information from both the power detector and peak detectors are used jointly to make gain changes.
►
Peak Detect Mode
In this mode, only the peak detectors are used to inform the AGC to make gain changes. This section explains the basic premise of the
operation, while the subsequent sections cover the more explicit details of configuring the peak detectors.
The APD and HB detector both have a high threshold and a low threshold, apdHighTresh, apdLowThresh, hbHighTresh, and hbUnderRange-
HighThresh, respectively. These levels are user programmable, as well as the number of times to exceed a threshold to flag an overrange
condition.
The high thresholds are used as limits on the incoming signal level and are principally set based on the maximum input of the ADC. When an
overrange condition occurs, the AGC reduces the gain (gain attack). The low thresholds are used as lower limits on the signal level. When an
underrange condition occurs, the AGC increases the gain (gain recovery). The AGC stable state (where it does not adjust gain) occurs when
neither an underrange nor overrange condition occurs.
Each overrange/underrange condition has its own attack and recovery gain step, as shown in
analog.com
TIA
Front-End Attenuator
Control
Control Word [7:0]
251 0
250 0
248 0
... ...
94 0
53 0
0 0
ADC
External Gain
Control
Control [1:0]
0 0
0 0
0 0
... ...
0 0
0 0
0 0
Gain Mode
Manual Gain Control SPI Mode
Manual Gain Control PIN Mode
Automatic Gain Control Mode
Rx Channel
Rx1
Rx2
Table 77.
ADRV9001
Digital Gain/Attenuator Con-
trol Word
Phase
[10:0]
Offset
0 +13
0 +16
0 −2
... ...
0 −9
0 −4
0 0
Table 75 shows the possible
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