Rainbow Electronics AT86RF211 - Manual (Page 21)

21
AT86RF211
1942C–WIRE–06/02
An automatic level control loop (ALC) is integrated, in order to minimize the sensitivity of
the PA to the temperature, process and power supply variations. For instance, at +85°C,
the output power is about 2 dB less than at 25°C. At -40°C, the output power is higher
than at 25°C. The ALC is controlled by a current which is generated in the following way:
Figure 26. ALC of the Power Amplifier
Figure 27. Typical Output Power of the PA for T = 25°C and V
CC
= 3V
Hardware Control The max output power is determined by R
POWER
and the maximum output power is
obtained with R
POWER
= 10 k
Ω
.
18 k
Ω
is the nominal value for a +10 dBm output in the 868 MHz frequency band.
Decreasing this value to 10 k
Ω
will lead to +14 dBm at 433 MHz, +12 dBm at 868 MHz,
+10 dBm at 915 MHz (typical values for conducted output power).
U
I
≅ 18 k Ω
digital
power control
DAC
I
OUT
To ALC
1.25 V
(v)
i
ref
=
V
R
POWER
3 bits
R
POWER
Output Power
-2
0
2
4
6
8
10
12
14
26 31 36 41 46 51 56 61
Isupply (mA)
Po
u
t (d
B
m
)
433MHz
868MHz
915MHz