Application Circuits; Basic Application Schematic - Atmel ATmega256RFR2 Manual

4 Application Circuits

4.1 Basic Application Schematic

8393CS-MCU Wireless-09/14
A basic application schematic of the ATmega256/128/64RFR2 with a single-ended RF
connector is shown in Figure 4-1 below
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 (64-pin package)
C1
RF
B1
C4
C2
Pins TST & CLKI
must be connected
CX3
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
Capacitors CB1 and CB3 are bypass capacitors for the integrated analog and digital
voltage regulators to ensure stable operation and to improve noise immunity.
ATmega256/128/64RFR2
and the associated Bill of Material in
CX1
CB2
V
DD
CB1
64 63 62 61 60 59 58 57
1
2
3
4
5
6 PF7
7 AVSS
8 RFP
9 RFN
10 AVSS
11 TST
RSTN
12
13 RSTON
14 PG0
15
16
17 18 19 20 21 22 23 24
CB3 CB4
XTAL
CX4
32kHz
7).
CX2
XTAL
56 55 54 53 52 51 50 49
48
47
PE0 46
45
DVSS
DEVDD 44
PB7
43
42
41
40
39
38
37
PB0 36
DVSS 35
DEVDD
34
33
25 26 27 28 29 30 31 32
V
DD
Table 4-1
CLKI
9