Analog Devices AD9361 Reference Manual page 29

AD9361 Reference Manual
ENSM and RF VCO Calibrations
The ENSM controls an internal signal that tells the Rx and Tx
synthesizers when to calibrate. In FDD, both the Rx and Tx
synthesizers calibrate when moving from WAIT to ALERT and
when the integer RF frequency word is written. Otherwise, the
synthesizers remain powered on and locked.
Similar to FDD, in TDD the enabled synthesizer (depending on
TXNRX logic level) will be calibrated when moving from WAIT
to ALERT. When in the ALERT, Rx, or Tx state, the enabled
synthesizer (depending on the TXNRX logic level) will calibrate
when the integer frequency word is written in the SPI register map.
FB_CLK
SPIWRITE
ENABLE
TXNRX
ENSM STATE[3:0]
WAIT
FB_CLK
SPIWRITE
ENABLE
TXNRX
ENSM STATE[3:0]
WAIT
SPIWRITE
POWER UP VCO
ALERT
LDO
Figure 14. FDD Independent Control, Level Mode
SPIWRITE
POWER UP VCO
ALERT
LDO
Figure
15. FDD Independent Control, Pulse Mode
In TDD, the synthesizers do not remain locked all the time.
While in the Rx state, the Tx synthesizer is disabled to save
power. While in the Tx state, the Rx synthesizer is disabled. In
TDD, the ENSM will generate a signal to recalibrate the correct
VCO anytime the state of TXNRX changes. This signal will be
issued from the ENSM to the synthesizer after the delay in Rx
or Tx Load Synth Delay has completed.
It is important to change the state of TXNRX as soon as the
device moves into the ALERT state to allow time for the
selected synthesizer to calibrate before moving into the Rx or
Tx states.
RX ENABLED RX DISABLED
TX ENABLED
FDD
RX DISABLED
RX ENABLED RX ENABLED
TX DISABLED TX ENABLED
FDD
Rev. A | Page 29 of 128
SPIWRITE
RX ENABLED
TX DISABLED
SPIWRITE
TX DISABLED
UG-570
ALERT
ALERT