ATA5425-PLSW datasheet(23/100 Pages) ATMEL

23 / 100 page

4841D–WIRE–10/07

ATA5423/ATA5425/ATA5428/ATA5429

Table 3-9 shows the relative changes of the output power of a typical device compared to

3.0V/25°C. As can be seen, a temperature change to –40°C as well as to +85°C reduces the

power by less than 1 dB due to the band gap regulated output current. Measurements of all the

cases in Table 3-7 on page 22 over temperature and supply voltage have shown about the same

relative behavior as shown in Table 3-9.

3.14

RX/TX Switch

The RX/TX switch decouples the LNA from the PA in TX mode, and directs the received power

to the LNA in RX mode. To do this, it has a low impedance to GND in TX mode and a high

impedance to GND in RX mode. To design a proper RX/TX decoupling, a linear simulation tool

for radio frequency design together with the measured device impedances of Table 3-1 on page

11, Table 3-7 on page 22, Table 3-10 and Table 3-11 on page 24 should be used, but the exact

element values have to be found on-board. Figure 3-11 shows an approximate equivalent circuit

of the switch. The principal switching operation is described here according to the application of

Figure 2-1 on page 7. The application of Figure 2.2 on page 8 works similarly.

Figure 3-11. Equivalent Circuit of the Switch

Table 3-9.

Measurements of Typical Output Power Relative to 3V/25°C

VS =

2.4V

3.0V

3.6V

amb = –40°C

–2.4 dB

–0.7 dB

0 dB

amb = +25°C

–1.6 dB

0 dB

+0.9 dB

amb = +85°C

–2.3 dB

–0.7 dB

+0.4 dB

Table 3-10.

Impedance of the RX/TX Switch RX_TX2 Shorted to GND

Frequency

Z(RX_TX1) TX Mode

Z(RX_TX1) RX Mode

315

MHz

(4.8 + j3.2)

Ω

(11.3

– j214)

Ω

345

MHz

(4.7 + j3.4)

Ω

(11.1

– j181)

Ω

433.92

MHz

(4.5 + j4.3)

Ω

(10.3

– j153)

Ω

868.3

MHz

(5 + j9)

Ω

(8.9

– j73)

Ω

915

MHz

(5 + j9.2)

Ω

– j65)

Ω

1.6 nH

2.5 pF

RX_TX1

Ω

ATA5425-PLSW Datasheet(PDF) 23 Page - ATMEL Corporation

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