MSC7118 Datasheet, PDF (42/60 Pages) Freescale Semiconductor, Inc – Low-Cost 16-bit DSP with DDR Controller

Hardware Design Considerations
3.2.2.2 Case 2
The power-up sequence is as follows:
1. Turn on the V_DDIO (3.3 V) supply first.
2. Turn on the V_DDC (1.2 V) and V_DDM (2.5 V) supplies simultaneously (second).
3. Turn on the V_REF (1.25 V) supply last (third).
Note: Make sure that the time interval between the ramp-up of V_DDIO and V_DDC/V_DDM is less than 10 ms.
The power-down sequence is as follows:
1. Turn off the V_REF (1.25 V) supply first.
2. Turn off the V_DDM (2.5 V) supply second.
3. Turn off the V_DDC (1.2 V) supply third.
4. Turn of the V_DDIO (3.3 V) supply fourth (last).
Use the following guidelines:
• Make sure that the time interval between the ramp-down for V_DDIO and V_DDC is less than 10 ms.
• Make sure that the time interval between the ramp-up or ramp-down for V_DDC and V_DDM is less than 10 ms for
power-up and power-down.
• Refer to Figure 27 for relative timing for Case 2.
Ramp-up
Ramp-down
V_DDIO = 3.3 V
V_DDM = 2.5 V
<10 ms
<10 ms
<10 ms
Time
Figure 27. Voltage Sequencing Case 2
V_REF = 1.25 V
V_DDC = 1.2 V
MSC7118 Low-Cost 16-bit DSP with DDR Controller Data Sheet, Rev. 7
42
Freescale Semiconductor