BGT24MTR11
User's Guide
Sensors
Application Note AN305, Rev. 1.0
2012-11-15
12 / 15
6
Sensors
BGT24MTR11 has three built in sensors for measuring TX-power, LO-power and chip temperature
All three sensors offer their readings via analog output voltages, which can be accessed via a multiplexer that
connects the single output voltages to the ANA pin (pin 25).
The table below shows which bits in the SPI data register need to be set to select the different sensor readings
at ANA.
Table 2
Truth table for analog multiplexer
Output signal at ANA
AMUX2 (bit 11)
AMUX1 (bit 8)
AMUX0 (bit 7)
P
OUT,TX
low
low
low
P
REF,TX
low
low
high
P
OUT,LO
low
high
low
P
REF,LO
low
high
high
V
TEMP
high
low
low
6.1
Power Sensors
For output power measurement, peak voltage detectors are connected to the output of the TX power amplifier
and to the LO medium power amplifier. To eliminate temperature and supply voltage variations, a reference
output voltage V
REF
is available through the ANA output for the TX and LO power sensor. The compensated
detector output voltage is given by the difference between V
OUT
and V
REF
for both power sensors. This voltage
difference is proportional to the RF voltage swing at the individual amplifier outputs, its characteristic is non-
directional.
Note: The actual voltage output of the power sensors is strongly dependant on the terminations of the amplifier
outputs since the power sensors are actually peak voltage detectors.
Figure 7
Transfer characteristics of power sensors
Transfer Function
Pout/dBm = 5.24*ln(
D
V/mV) - 23.74
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
50
100
150
200
250
300
350
400
P
o
u
t
/
d
B
m
D
V / mV
Output Power vs.
D
V = (V
OUT,TX
- V
REF,TX
)
Measurement
Model
