AX5051
www.onsemi.com
6
DC Characteristics
Table 3. SUPPLIES
Symbol Description Condition Min Typ Max Units
T
AMB
Operational ambient temperature −40 27 85 °C
VDD_IO I/O and voltage regulator supply voltage
RX operation or TX operation
up to 4 dBm output power
2.2 3.0 3.6 V
TX operation up to 16 dBm
output power
2.4 3.0 3.6 V
VREG Internally regulated supply voltage
Power−down mode
PWRMODE=0x00
1.7 V
All other power modes 2.1 2.5 2.8 V
VREG
droptyp
Regulator voltage drop RX operation or TX operation
up to 4 dBm output power
50 mV
VREG
dropmax
Regulator voltage drop at maximum internal
current consumption
TX mode with 16 dBm output
power
300 mV
I
PDOWN
Power−down current PWRMODE = 0x00 0.5
mA
I
RX−HS
Current consumption RX
High sensitivity mode:
VCO_I = 001; REF_I = 011
Bit rate 10 kbit/s 19 mA
I
RX−LP
Current consumption RX
Low power mode:
VCO_I = 001; REF_I = 101
Bit rate 10 kbit/s 17 mA
I
TX
Current consumption TX
VCO_I = 001; REF_I = 011; LOCURST = 1,
(Note 1)
868 MHz, 15 dBm 45
mA
433 MHz, 15 dBm 45
TX
varvdd
Variation of output power over voltage VDD > 2.5 V ± 0.5 dB
TX
vartemp
Variation of output power over temperature VDD > 2.5 V ± 0.5 dB
1. The PA voltage is regulated to 2.5 V. Between 2.2 V and 2.55 V VDD_IO a drop of 1 dBm of output power is visible.
Note on Current Consumption in TX Mode
To achieve best output power the matching network has to
be optimized for the desired output power and frequency. As
a rule of thumb a good matching network produces about
50% efficiency with the AX5051 power amplifier although
over 90% are theoretically possible. A typical matching
network has between 1 dB and 2 dB loss (P
loss
).
The current consumption can be calculated as
I
TX
[mA] +
1
PA
efficiency
10
ǒ
P
out
[dBm])P
loss
[dB]
10
Ǔ
B 2.5V ) I
offse
I
offset
is about 12 mA for the VCO at 400−470 MHz and
11 mA for 800−940 MHz. The following table shows
calculated current consumptions versus output power for
P
loss
= 1 dB, PA
efficiency
= 0.5 and I
offset
= 11 mA at 868 MHz.
Table 4.
Pout [dBm] I [mA]
0 13.0
1 13.2
2 13.6
3 14.0
4 14.5
5 15.1
6 16.0
7 17.0
8 18.3
9 20.0
10 22.0
11 24.6
12 27.96
13 32.1
14 37.3
15 43.8
The AX5051 power amplifier runs from the regulated
VDD supply and not directly from the battery. This has the
advantage that the current and output power do not vary
much over supply voltage and temperature from 2.55 V to
3.6 V supply voltage. Between 2.55 V and 2.2 V a drop of
about 1 dB in output power occurs.
