AX5243 datasheet(7/42 Pages) ONSEMI

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AX5243

www.onsemi.com

For information on current consumption in complex

modes of operation tailored to your application, see the

software AX−RadioLab for AX5243.

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 AX5243 power amplifier although

over 90% are theoretically possible. A typical matching

network has between 1 dB and 2 dB loss (Ploss). The PA is

internally multiplexed with the LNA on pins ANTP and

ANTN. Therefore constraints for the RX matching have to

be considered for the PA matching.

The current consumption can be calculated as

ITX[mA] +

PAefficiency

Pout[dBm])Ploss[dB]

B 1.8V ) Ioffset

Ioffset is about 6 mA for the fully integrated VCO at

400 MHz to 1050 MHz, and 3 mA for the VCO with external

inductor at 169 MHz. The following table shows calculated

current consumptions versus output power for Ploss = 1 dB,

PAefficiency = 0.5, Ioffset = 6 mA at 868 MHz and

Ioffset = 3.5 mA at 169 MHz.

Table 4. CURRENT CONSUMPTION VS. OUTPUT

POWER

Pout [dBm]

Itxcalc [mA]

868 MHz

169 MHz

7.5

4.5

7.9

4.9

8.4

5.4

9.0

6.0

9.8

6.8

10.8

7.8

12.1

9.1

13.7

10.7

15.7

12.7

18.2

15.2

21.3

18.3

25.3

22.3

30.3

27.3

36.7

33.7

44.6

41.6

54.6

51.6

Both AX5243 power amplifiers run from the regulated

VDD_ANA 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.

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