mcf5407 Freescale Semiconductor, Inc, mcf5407 Datasheet - Page 479

• Manufacturer Part Number: mcf5407
• Description: Mcf5407 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

20.1.1 Supply Voltage Sequencing and Separation Cautions
Figure 20-1 shows two situations to avoid in sequencing the IV
IV
for the IV
(Figure 20-2). This keeps IV
IV
supplies (2). Typically this situation is avoided by using external discrete diodes in series
between supplies as shown in Figure 20-2. The series diodes forward bias when the
difference between EV
ramps up. When the IV
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: EV
these constraints just as IV
with some filtering.
cc
cc
should not be allowed to rise early (1). This is usually avoided by running the regulator
should not rise so late that a large voltage difference is allowed between the two
1.8V
3.3V
Notes:
1
2
Figure 20-1. Supply Voltage Sequencing and Separation Cautions
0
cc
IV
EV
cc
cc
supply (1.8 V) from the voltage generated by the 3.3-V EV
, PV
cc
rising much faster than IV
≥ IV
cc
rising before EV
1
cc
cc
cc
≥ (EV
and IV
regulator begins proper operation, the difference between supplies
cc
Chapter 20. Electrical Specifications
cc
does. In practice, PV
cc
from rising faster than EV
cc
cc
- 2.1 V). The PLL Vdd (PV
reaches approximately 2.1V, causing IV
cc
, PV
2
cc
Supplies Stable
cc
is typically connected directly to IV
cc
.
cc
) supply should comply with
cc
and EV
IV
EV
cc
, PV
cc
General Parameters
cc
cc
cc
supplies.
to rise as EV
Time
cc
supply
20-3
cc
cc