Atmel ATmega128RFR2, Manual

Page: 9 / 14

9
8393CS-MCU Wireless-09/14
ATmega256/128/64RFR2
4 Application Circuits
4.1 Basic Application Schematic
A basic application schematic of the ATmega256/128/64RFR2 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 50
Ω
single-ended RF input is transformed to the 100
Ω
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 (64-pin package)
8
7
6
5
4
3
2
1
17 18 19 20 21 22 23 24
56 57 58 59 60 61 62 63
A
R
E
F
A
V
S
S
AVSS
RFP
RFN
AVSS
TST
D
V
S
S
D
V
D
D
D
V
D
D
X
T
A
L
2
D
E
V
D
D
D
V
S
S
A
V
D
D
E
V
D
D
A
V
S
S
X
T
A
L
1
41
42
43
44
45
46
47
48
PB0
DVSS
PE0
PB7
CB3 CB4
RSTN
V
DD
XTAL
CX1 CX2
CB1
V
DD
CB2
C1
C2
B1
RF
C4
25 26 27 28 29 30 31 32
16
14
13
12
11
10
9
15
64 54 55 49 50 51 52 53
33
34
35
36
37
38
39
40
RSTON
XTAL
32kHz
CX3 CX4
CLKI
DEVDD
DVSS
DEVDD
P
E
7
D
V
S
S
D
E
V
D
D
P
F
0
PF7
PG0
P
G
5
P
D
0
P
D
7
Pins TST & CLKI
must be connected
The power supply bypass capacitors (CB2, CB4) are connected to the external analog
supply pin (EVDD, pin 59) and external digital supply pin (DEVDD, pin 23). Pins 34, 44
and 54 supply the digital port pins.
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.