SCF5249VM140 FREESCALE [Freescale Semiconductor, Inc], SCF5249VM140 Datasheet - Page 31

• Manufacturer Part Number: SCF5249VM140
• Description: Integrated ColdFire Microprocessor
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

When a DC-DC convertor is used in the system to generate the 1.8V supply, additional care is required. If
possible, the 1.8V DC-DC convertor should be supplied by the 3.3V supply. If this is impossible or
considered inefficient, the designer needs to ensure that the rise time of the 1.8V supply still complies with
the recommendations stated above. Adding the 3 diodes will help resolve issues associated with a slow rise
time of the 1.8V supply. Further, a Schotty diode could be added between the supplies, which would have
the effect of holding the 1.8V supply to match the 3.3V supply should the 1.8V supply come-up first. This
diode also has the function of ensuring that there is not a large voltage differential between the Core supply
and the PAD supply during power-down.
Refer to the M5249C3 Reference Board Userís Manual for the recommended diode types.
A further note is the recommendation for hard resetting of the device. Freescale recommends using a
dynamic reset circuit. This allows for control of the voltage at which the reset will be released and ensure
that the correct voltage level at the RESET pin is achieved in all cases. Passive (RC) reset networks do not
always achieve the desired results.
Freescale Semiconductor
The following signals are not available on the 144 QFP package.
160MAPBGA Ball
SCF5249 Integrated ColdFire® Microprocessor Data Sheet, Rev. 3
Number
Figure 3. Example Circuit to Control Supply Sequencing
G4
E3
H3
K3
Table 18. 160 MAPBGA Ball Assignments
Figure 4. SCF5249 Power Supply
RSTO/SDATA2_BS2
SDATA0-SDIO1
CMD_SDIO2
Function
A25
NOTE
GPIO34
GPIO54
GPO8
GPIO
Electrical Characteristics
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