Micom_Electric/마이컴_원칩
2011. 8. 25. 23:18
http://www.mypic32.com/web/guest/forums/message_boards/message/79635
2.5-3.6V operation, 5V tolerant I/Os
9/3/08 8:49 PM I'm a bit insecure what "2.5-3.6V operation, 5V tolerant I/Os" really means. Should Iread this as I can feed a 5V signal on any pin of the PIC32MX? For instance if I have a chip that is on 5V using SPI SDO can be connected directly to the PIC32MX without any level shifters?
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RE: 2.5-3.6V operation, 5V tolerant I/Os
9/3/08 9:38 PM as a reply to akhe . Yep, except for the exceptions.
Watch out for the pins that can be used as analog inputs and MCLR/Vpp. To quote Microchip:
Digital only pins are capable of input voltages up to
5.5V. Any pin that shares digital and analog functionality is limited to voltages up to VDD + 0.3V. The MCLR/Vpp might be safe on the PIC32, but I'd still avoid it. | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/3/08 9:57 PM as a reply to akhe . You must also set the output pin to open drain.
Setting a bit in the ODCx register = 1 configures the corresponding pin as an open-drain output. The open-drain feature allows the generation of outputs higher than VDD, e.g., 5V, on any desired digital-only pins by using external pull-up resistors. | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/4/08 1:34 AM as a reply to akhe . Like jgray and jedetech said, for inputs the PIC32MX family is "5V tolerant" but not all pins have that feature,
pins that are shared with the ADC module (PORTb) do not support it for example. There are some considerations you have to also take in account, for example in some situations if you are feeding a high speed 5V pulsing signal to some of this ports, you may have excesive "undershoots" (the tiny pulses that on a scope you may see ringing on the bottom of the signal edges and going negative), they may exceed the max negative voltage for a particular input, one way to avoid that is to put a resistor (200-470 typical) in series to soften that. Another consideration, particularly for a SPI interface, yes you can connect SDO of a 5V part to the SDI pin on the PIC32, but for the other direction the open drain configuration will not work properly and you may need to use a level converter. My .02 | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/4/08 6:32 AM as a reply to jamodio . Thanks a lot everyone. Exactly the information I needed. I need to connect a MCP2515 ( CAN ) on 5V to my prototype so I have som SPI also that needs to be connected. In the end I probably will use a level shifter between the MCP2515 and the 2551 tranceiver instead but is a bit worried about speed issues there.
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RE: 2.5-3.6V operation, 5V tolerant I/Os
9/4/08 2:21 PM as a reply to akhe . Level-shifting should not introduce a speed problem.
Try a 74VHCT125 - two of these are found on the SD/MMC PICtail, used to interface the SD card (3.3V) to the PICtail signals (can be 5V or 3.3V). Pete | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/6/08 3:59 PM as a reply to akhe . The PIC32MX family is currently specified to operate between 2.3v and 3.6v VDD. This is in table 30-1 of the currentPIC32MX Family Data sheet
Clayton Pillion PIC32 Marketing | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/6/08 4:47 PM as a reply to akhe . If you go to www.Microchip.com/3volts and check out Tips & Tricks page 8-12, it shows an example using the MCP2515 and MCP2551 with a unidirectional level translator and a bidirectional translator circuits. The app note also includes other 3.3/5volt interfaces......
here is the link to the document 3V Tips & Tricks | |
RE: 2.5-3.6V operation, 5V tolerant I/Os
9/13/08 3:32 PM as a reply to bmorse . Thanks all for your kind replies!
Cheers /Ake |