M5249C3 Freescale Semiconductor, M5249C3 Datasheet - Page 30

• Manufacturer Part Number: M5249C3
• Description: KIT EVAL FOR M5249 W/ETHERNET
• Manufacturer: Freescale Semiconductor
• Series: ColdFire®r
• Type: Microprocessorr

Specifications of M5249C3

• Contents: Module and Misc Hardware
• Processor To Be Evaluated: MCF5249
• Interface Type: RS-232, Ethernet
• For Use With/related Products: MCF5249
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Electrical Characteristics
9.1
Supply Voltage Sequencing and Separation Cautions
Figure 2
shows two situations to avoid in sequencing the CoreVdd and PADVdd (I/O) and PLLL supplies.
Figure 2. Supply Voltage Sequencing and Separation Cautions
CoreVdd supply should not be allowed to rise early (1). This is usually avoided by running the regulator
for the CoreVdd supply (1.8 V) from the voltage generated by the 3.3V supply (PADVdd). This keeps the
CoreVdd supply from rising faster than PADVdd supply.
Also CoreVdd, PLLGVdd, PLLCVdd supply should not rise so late that a large voltage difference is
allowed between the two supplies (2). Typically this situation is avoided by using external discrete diodes
in series between supplies. The series diodes forward bias when the difference between PADVdd and
CoreVdd reaches approximately 2.1V, causing CoreVdd to rise as PADVdd ramps up. When the CoreVdd
regulator begins proper operation, the difference between supplies should not exceed 1.5 V and conduction
through the diode chain reduces to essentially leakage current.
During supply sequencing, the following general relationship should be adhered to: PADVdd, >=
CoreVdd, PLLGVdd, >= (PADVdd - 2.1 V).
The PLL core supplies (PLLGVdd and PLLCVdd) should comply with these constraints just as the
CoreVdd does. In practice, PLLGVdd and PLLCVdd are typically connected directly to the CoreVdd with
some filtering. Further, the PLL PAD supply (PLL1VDD) would be connected directly to the PAD supply
via some filtering.
SCF5249 Integrated ColdFire® Microprocessor Data Sheet, Rev. 3
30
Freescale Semiconductor