9

42073BS-MCU Wireless-09/14

ATmega2564/1284/644RFR2

4 Application Circuits

4.1 Basic Application Schematic

A basic application schematic of the ATmega2564/1284/644RFR2 with a single-ended

RF connector is shown in Figure 4-1 below and the associated Bill of Material in Table

4-1 on page 10. The 50Ω single-ended RF input is transformed to the 100Ω differential

RF port impedance using Balun B1. The capacitors C1 and C2 provide AC coupling of

the RF input to the RF port, capacitor C4 improves matching.

Figure 4-1. Basic Application schematic (48-pin package)

6

5

4

3

2

1

13

14

15

16

17

18

19

20

40

41

42

43

44

45

46

47

AVSS

RFP

RFN

AVSS

TST

31

32

33

34

35

36

PE0

CB3

CB4

RSTN

XTAL

CX1

CX2

CB1

CB2

B1

RF

C4

21

22

23

24

12

11

10

9

8

7

48

38

39

37

25

26

27

28

29

30

XTAL

32kHz

CX3

CX4

CLKI

PB0

PB7

PF7

PG1

Pins TST & CLKI

must be connected

PG3

PF3/4

C1

The power supply bypass capacitors (CB2, CB4) are connected to the external analog

supply pin (EVDD, pin 44) and external digital supply pin (DEVDD, pin 16). The

capacitor C1 provides the required AC coupling of RFN/RFP.

Floating pins can cause excessive power dissipation (e.g. during power on). They

should be connected to an appropriate source. GPIO shall not be connected to ground

or power supply directly.

The digital input pins TST and CLKI must be connected. If pin TST will never be used it

can be connected to AVSS while an unused pin CLKI could be connected to DVSS (see

chapter "Unused Pins" on page 7).

Capacitors CB1 and CB3 are bypass capacitors for the integrated analog and digital

voltage regulators to ensure stable operation and to improve noise immunity.

Capacitors should be placed as close as possible to the pins and should have a low-

resistance and low-inductance connection to ground to achieve the best performance.