5282 spi 5v
Posted: Mon Jun 27, 2011 6:47 am
Anyone know if the 5282 is 5v tolerant on the spi bus? or do we need a level converter?
While many of the I/O pins on the MOD5282 are 5V tolerant I would still use a level converter here. The MCF5282UM document states that the max voltage for an input is 5.25V, all other processors NetBurner uses are 3.6V max. You have to be careful not to use 5V on any input pins that may be connected to another device on the module. One example would be the data bus lines that connect to SDRAM. The SPI signals are not connected to anything else so this should be fine.
The problem you will have with this is 5V tolerance is not the same as 5V compatible. 5V tolerant means that an input of 5V is okay but it will not drive an output any higher then Vdd, 3.3V in this case. According to the electrical specifications, the MOD5282 will be driving its output at somewhere between 2.7V-3.3V... most likely closer to 3.3V. The 5V SPI device you are talking to probably wants the Vih ( input high voltage ) to have a minimum of 0.7xVdd, 3.5V on a 5V part. The device may work if the minimum input voltage is not met but stability and compatibility is not guaranteed. A $0.30 level converter may save you hours of debugging and potential reworking.