Auxadc - Analog Devices AD9361 Reference Manual

AD9361 Reference Manual

AuxADC

The AuxADC is a 12-bit auxiliary converter with an input level
range 0 V to 1.3 V with an adjustable conversion time. The
AuxADC is configured using the ad9361_auxadc_setup
function. The AuxADC allows monitoring of desired voltages
such as a PA power detector or an external temperature sensor.
A small value capacitor (680 pF) may be placed on the
AUXADC pin to improve noise performance. The
includes an internal temperature sensor that can be measured
using the AuxADC. Note that the AuxADC can only be used to
measure either the internal temperature or the voltage on the
AUXADC pin at a time.
Figure 56 shows the AuxADC code vs. input voltage. The
AuxADC is off by default. The AuxADC clock is generated by
dividing the baseband PLL frequency. Equation 21 and
AuxADC Clock Frequency
AuxADC Decimation = 256 × 2
Table 45. Example Code for AuxADC Set Up
Command Address(hex)
SPI Write 0F
SPI Write 1C
SPI Write 1D
SPI Write 35
SPI Write 36
AD9361 also
BBPLL Frequency


1 AuxADC Clock Divider
AuxADC Decimation[2:0]
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0 512 1024
AUXDAC CODE (Decimal)
Figure 56. AuxADC Code vs. Input Voltage
Data(hex)
4
63
0
1E
FF
Rev. A
Equation 22 determine the AuxADC clock frequency and the
decimation rates.
The AuxADC output is read from Register 0x1E (D7:D0) and
Register 0x1F (D3:D0). To capture the voltage on the
AUXADC pin, the decimation filter clock should be routed on
the CTRL_OUT0 pin. To select the AuxADC decimation clock
on the CTRL_OUT0 pin write Register 0x35 to Register 0x1E.
Data from Register 0x1E (D7:D0) and Register 0x1F (D3:D0)
can be latched on the falling edge or on the rising edge of
decimation clock coming out of the CTRL_OUT0 pin. The SPI
reads must occur before the edge on the control out signal
toggles again.
The register settings used during the ramp test shown in
Figure 56 are shown in Table 45.
[ : 5 ] 0
1536 2048 2560 3072 3584
Comment
Disable temp sensor read back
Set the AuxADC clock frequency to BBPLL/36
Enable AuxADC and set decimation to 256
Select AuxADC valid on control out [0]
Enable all control out pins
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