attiny167-esxz ATMEL Corporation, attiny167-esxz Datasheet - Page 244

• Manufacturer Part Number: attiny167-esxz
• Description: 8-bit Avr 8-bit Microcontroller Microcontroller With 16k Bytes In-system Programmable Flash And Lin Controller
• Manufacturer: ATMEL Corporation

23. Decoupling Capacitors
244
ATtiny167
The operating frequency (i.e. system clock) of the processor determines in 95% of cases the
value needed for microcontroller decoupling capacitors.
The hypotheses used as first evaluation for decoupling capacitors are:
•
•
Figure 23-1. Capacitor description
According to the operating frequency of the product, the decoupling capacitances are chosen
considering the frequencies to filter,
The relation between frequencies to cut and decoupling characteristics are defined by:
where:
Then, in normalized value range, the decoupling capacitors become:
Table 23-1.
These decoupling capacitors must to be implemented as close as possible to each pair of power
supply pins:
Nevertheless, a bulk capacitor of 10-47 µF is also needed on the power distribution network of
the PCB, near the power source.
For further information, please refer to Application Notes AVR040 “EMC Design Considerations“
and AVR042 “Hardware Design Considerations“ on the Atmel web site.
The operating frequency (
peaks are located at
An SMC capacitor connected to 2 micro-vias on a PCB has the following characteristics:
–
–
–
–
–
–
1.5 nH from the connection of the capacitor to the PCB,
1.5 nH from the capacitor intrinsic inductance.
L: the inductance equivalent to the global inductance on the Vcc/Gnd lines.
C
16-17 for logic sub-system,
5-6 for analogical sub-system.
f
1
op
& C
, operating frequency
Decoupling Capacitors vs. Frequency
2
: decoupling capacitors (C
16 MHz
12 MHz
10 MHz
8 MHz
6 MHz
4 MHz
f
op
and 2 •
f
op
0.75 nH
) supplies itself the maximum peak levels of noise. The main
f
op
f
f
op
op
=
.
and 2 •
---------------------- -
2Π LC
1
1
= 4 • C
Capacitor
1.5 nH
1
f
op
.
2
).
120 nF
220 nF
560 nF
33 nF
56 nF
82 nF
C
and
1
0.75 nH
2
PCB
•
f
op
=
---------------------- -
2Π LC
1
120 nF
10 nF
15 nF
22 nF
33 nF
56 nF
7728A–AUTO–07/08
C
2
2