ATA5423-PLSW datasheet(21/100 Pages) ATMEL

21 / 100 page

4841D–WIRE–10/07

ATA5423/ATA5425/ATA5428/ATA5429

Example:

According to Table 3-7 on page 22, with a frequency of 433.92 MHz and output power of

11 dBm the overall current consumption is typically 17.8 mA; hence, the PA needs

17.8 mA - 6.95 mA = 10.85 mA in this mode, which corresponds to an overall power amplifier

efficiency of the PA of (10

(11dBm/10)

× 1 mW)/(3 V × 10.85 mA) × 100% = 38.6% in this case.

Using a higher resistor in this example of R

1 =1.091 × 22 kΩ =24kΩ results in 9.1% less cur-

rent in the PA of 10.85 mA/1.091 = 9.95 mA and 10

× log(1.091) = 0.38 dB less output power if

using a new load resistance of 300

Ω× 1.091 = 327Ω. The resulting output power is then

11 d B m – 0 . 38 d B = 1 0.6 d Bm

a n d

th e

o v er all

cu rre nt

con s um ptio n

6.95 mA + 9.95 mA = 16.9 mA.

The values of Table 3-7 on page 22 were measured with standard multi-layer chip inductors with

quality factors Q according to Table 3-7 on page 22. Looking to the 433.92 MHz/11 dBm case

with the quality factor of Q

L1 = 43 the loss in this inductor is estimated with the parallel equivalent

resist ance of the induct o r R

los s =2 ×π × f × L × Q L1 and the mat c hing loss with

10 log (1 + R

Lopt/Rloss) which is equal to 0.32 dB losses in this inductor. Taking this into account,

the PA efficiency is then 42% instead of 38.6%.

Be aware that the high power mode (PWR_H = AVCC) can only be used with a supply voltage

higher than 2.7V, whereas the low power mode (PWR_H = GND) can be used down to 2.4V as

can be seen in the “Electrical Characteristics: General” on page 67.

The supply blocking capacitor C

2 (10 nF) has to be placed close to the matching network

because of the RF current flowing through it.

Figure 3-10. Power Setting and Output Matching

RFOUT

RF_OUT

VPWR_H

AVCC

ATA5423/ATA5425/

ATA5428/ATA5429

PWR_H

R_PWR

ATA5423-PLSW 数据表(PDF) 21 Page - ATMEL Corporation

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