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AVR Hardware Design Considerations [APPLICATION NOTE]

Atmel-2521M-AVR-Hardware-Design-Considerations_ApplicationNote_092014

Figure 5-1.

(A) Basic Schematic of Required/Recommended Connections for ATxmega32A4. (B) Copper PCB

Layout and (C) Top Silk Prints

(A)

Содержание AVR042

Страница 1: ...on to potential design problems rather than being an exhaustive walk through of how to design applications using the AVR microcontrollers This document is thus a collection of information from existin...

Страница 2: ...SPI Programming Interface 6 3 1 1 Shared Use of SPI Programming Lines 7 3 2 JTAG Interface 7 3 2 1 Shared Use of JTAG Lines 8 3 3 PDI Interface 9 3 3 1 External Reset Circuitry 9 3 4 TPI Interface 10...

Страница 3: ...tor Figure 1 1 Incorrect Decoupling Figure 1 1 shows an example of insufficient decoupling The capacitor is placed too far away from the microcontroller creating a large high current loop The power an...

Страница 4: ...n the same manner as the digital supply voltage AREF must also be decoupled a typical value for the capacitor is 100nF If a separate analog ground AGND is present the analog ground should be separated...

Страница 5: ...since this is not internally provided due to High Voltage Programming Alternatively or in addition a Zener diode can be used to limit the RESET voltage relative to GND The Zener diode is highly recomm...

Страница 6: ...Tools help for further information on which interfaces are supported by the device and how to connect the programming tool 3 1 SPI Programming Interface On devices that use a Serial Peripheral Interfa...

Страница 7: ...d to have only one ISP interface on the target board the ISP programming can be designed so that only one of the AVR devices is provided with a SPI clock at a time All other SPI lines can then be shar...

Страница 8: ...inciple is shown in Figure 3 4 and is explained in further detail in the AVR Tools help file Figure 3 4 JTAG Daisy Chain Protection resistors as shown in Figure 3 2 are necessary if the JTAG lines are...

Страница 9: ...h Atmel programmers Only two pins on the device are needed for use of this interface RESET also called PDI_CLK and the dedicated PDI_DATA pin The target s voltage supply is made available to allow for...

Страница 10: ...e to the fact that the use of these clock sources is not well understood This section therefore treats the topic of using crystals and ceramic resonators in relation to Atmel AVR MCUs The description...

Страница 11: ...s refer to both devices Table 4 1 Style tt table title Ceramic Resonator Quartz Crystal Aging 3000ppm 10ppm Frequency tolerance 2000 5000ppm 20ppm Frequency temperature characteristics 20 50ppm C 0 5p...

Страница 12: ...symmetric layout so that CL1 CL2 C and CL1S CL2S CS then the external capacitors can be determined by Equation 4 2 CS can be estimated to be 5pF 10pF Equation 4 2 S L C C C 2 4 3 Recommended Capacito...

Страница 13: ...counter can through this feature be used for real time functions A 32 768kHz crystal should then be connected to the TOSCx pins of the AVR In some AVRs the internal oscillator circuit used with the re...

Страница 14: ...derations APPLICATION NOTE Atmel 2521M AVR Hardware Design Considerations_ApplicationNote_092014 14 Figure 5 1 A Basic Schematic of Required Recommended Connections for ATxmega32A4 B Copper PCB Layout...

Страница 15: ...AVR Hardware Design Considerations APPLICATION NOTE Atmel 2521M AVR Hardware Design Considerations_ApplicationNote_092014 15 B C...

Страница 16: ...AVR Hardware Design Considerations_ApplicationNote_092014 16 6 Revision History Doc Rev Date Comments 2521M 09 2014 Fixed some typos in Section 2 1 2521L 07 2013 Updated the diagram of Filters on JTA...

Страница 17: ...NESS INTERRUPTION OR LOSS OF INFORMATION ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES Atmel makes no representations or wa...