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MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

40 Freescale Semiconductor

System Design Information

9.2.3 Transient Specifications

The ensure the long-term reliability of the device, the MPC7448 requires that transients on the core power

rail (V

) be constrained. The recommended operating voltage specifications provided in Table 4 are DC

specifications. That is, the device may be operated continuously with V

within the specified range

without adversely affecting the device’s reliability. Excursions above the stated recommended operation

range, including overshoot during power-up, can impact the long-term reliability of the device. Excursions

are described by their amplitude and duration. Duration is defined as the time period during which the V

power plane, as measured at the VDD_SENSE pins, will be within a specific voltage range, expressed as

percentage of the total time the device will be powered up over the device lifetime. In practice, the period

over which transients are measured can be any arbitrary period of time that accurately represents the

expected range of processor and system activity. The voltage ranges and durations for normal operation

and transients are described in Table 14.

Note that, to simplify transient measurements, the duration of the excursion into the High Transient region

is also included in the Low Transient duration, so that only the time the voltage is above each threshold

must be considered. Figure 19 shows an example of measuring voltage transients.

Figure 19. Voltage Transient Example

Table 14. VDD Power Supply Transient Specifications

At recommended operating temperatures. See Ta bl e 4 .

Voltage Region

Voltage Range (V)

Permitted

Duration

Notes

Min Max

Normal V

minimum V

maximum 100% 2

Low Transient V

maximum 1.35 V 10% 2, 3

High Transient 1.35 V 1.40 V 0.2% 4

Notes:

1. Permitted duration is defined as the percentage of the total time the device is powered on that the V

power supply voltage may exist within the specified voltage range.

2. See Table 4 for nominal V

specifications.

3. To simplify measurement, excursions into the High Transient region are included in this duration.

4. Excursions above the absolute maximum rating of 1.4 V are not permitted; see Ta bl e 2.

DD (nominal)

1.40 V

A + B < T • 10%

1.35 V

DD (maximum)

C < T • 0.2%

DD (minimum)

Normal

Low Transient

High Transient

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 59 60

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