Internal Temperature Sensor - Analog Devices AD9361 Reference Manual

UG-570

INTERNAL TEMPERATURE SENSOR

The AuxADC can also be used to measure the internal
temperature of the DUT. To measure the temperature sensor,
use the ad9361_auxadc_setup function to configure the part in
temperature sensor mode, and then use the ad9361_get_temp
function to do a reading. The temperature word has a slope of
approximately 1.14 LSB/°C. A single point factory or bench
calibration is required to equate absolute temperature to the
temperature word.
Bits[D2:D0] of Register 0x0F set the decimation rate for
AuxADC in temperature sensor mode per Equation 23.
For temperature measurement, the clock frequency of the
AuxADC is set to the frequency of BBPLL divided by 64.
Bits D7:D1 of Register 0x0D set the rate at which the
Temp Sensor Decimation = 256 × 2

Calculatio n Time ( s )
Table 46. Example Code for Temperature Sensor Setup
Command Address(hex)
SPI Write B
SPI Write C
SPI Write D
SPI Write F
SPI Write 1D
SPI Write 35
SPI Write 36
Temp Sensor Decimation[2:0]
Measuremen t Time Interval [
BBPLL Clock Frequency
180
160
140
120
100
80
60
40
20
0
–50 –40 –30 –20
Figure 57. AuxADC Measuring Internal Temp Sensor
Data(hex)
0
F
0
0
1
1E
FF
temperature sensor periodically takes temperature readings as
per Equation 24. If temperature measurements are to be
performed manually (Bit D0 of Register 0x0D is clear) then the
measurements start when Bit D0 of Register 0x0C (Start Temp
Reading) is set.
Data from register 0x0E can be latched into the baseband
processor on the toggle of the temp sensor valid signal, Bit D1
of Register 0x0C. This signal should be routed out on the
CTRL_OUT1 pin by writing 0x36 to Register 0x03.
Figure 57 shows the temperature sweep of the
reading the internal temperature sensor. Table 46 specifies the
register settings used to generate the internal temperature
sensor graph plotted in Figure 57.

29
: 6 ] 0 2
( Hz )
–10 0 10 20 30 40 50 60
TEMPERATURE (°C)
Comment
Set the Temp sense offset to 0
Temp sensor set in manual mode
Calculation time set to 0sec
Set the temp sensor decimation to 256
Disable AuxADC pin voltage measurement
Select Temp sense valid on control out [1]
Enable all control out pins
Rev. A
| Page 84 of 128
AD9361 Reference Manual
70 80 90
AD9361 while
(23)
(24)