AN2077 Motorola / Freescale Semiconductor, AN2077 Datasheet - Page 14

• Manufacturer Part Number: AN2077
• Description: PowerPC Design Checklist
• Manufacturer: Motorola / Freescale Semiconductor

1.4 Power
The PowerPC family has restrictions on the amount of time any power pin can be at a non-standard voltage
in relation to another power pin. Typically these event occur during power-up and power-down. When the
restrictions are not met, if the amount of time exceeds approximately 500uS, damage to the part may occur.
If the power supply can sequence all the I/O voltage (OVDD), L2 I/O voltage (L2OVDD), and core voltage
(VDD) within the specification limits, or stabilize within 500 uS, then no further design work is needed.
Otherwise, power supply sequencing assistance is needed. The easiest way is to apply a diode voltage
sourcing network as shown in the hardware specifications, but other means such as MOSFETs configured
as linear regulators are suitable as well. The diode solution supplies just under the targeted operating
voltage, but within the differential allowances in the hardware specification. Each device has slightly
different allowances, so refer to the hardware specifications for particular examples of diode networks for
each device.
Note that the diode network is needed for each non-compliant power supply. However, it is not needed
between all power supplies, only between those which are too slow. Thus, if OVDD (typically 3.3V) is
stable first and last, the others can be derived from it alone.
1.5 Clocks
All clocks should be carefully routed to be of equal lengths within similar domains (PowerPC system bus,
memory bus, or PCI bus). Devices with integrated clock drivers make this relatively easy; see the hardware
specifications, or the MPC107 Application Guide for further details.
1.6 References
The reference materials shown in Table may be useful to the designer. To locate the documents, go to
http://www.motorola.com/ and search for the document title.
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MPC107 Hardware Specification
MPC107 Design Guide
PowerPC 603e™ Hardware Specifications (PID6)
PowerPC 603e Hardware Specifications (PID7t)
MPC750A Hardware Specification
MPC7400 Hardware Specifications
MPC8240 Integrated Processor Hardware Specifications
Description
Table 4. Reference Material
PowerPC Design Checklist
MPC107EC/D
AN1849/D
MPC603EEC/D R2
MPC603E7TEC/D R3
MPC750EC/D
MPC7400EC/D
MPC8240EC/D
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