MPC8315ECVRAGDA datasheet(12/112 Pages) FREESCALE

12 / 112 page

MPC8315E PowerQUICC™ II Pro Processor Hardware Specifications, Rev. 0

Freescale Semiconductor

Electrical Characteristics

3.2

Power Sequencing

The MPC8315E does not require the core supply voltage (VDD and VDDC) and I/O supply voltages

(GVDD, LVDDx_ON, LVDDx_OFF, NVDDx_ON and NVDDx_OFF) to be applied in any particular

order. During the power ramp up, before the power supplies are stable, if the I/O voltages are supplied

before the core voltage, there may be a period of time when all input and output pins be actively driven

and cause contention and/or excessive current. In order to avoid actively driving the I/O pins and to

eliminate excessive current draw, apply the continuous core voltage (VDDC) before the continuous I/O

voltages (LVDDx_ON and NVDDx_ON) and switchable core voltage (VDD) before the switchable I/O

voltages (GVDD, LVDDx_OFF, and NVDDx_OFF). PORESET should be asserted before the continuous

power supplies fully ramp up. In the case where the core voltage is applied first, the core voltage supply

must rise to 90% of its nominal value before the I/O supplies reach 0.7 V, see Figure 3. Once all the power

supplies are stable, wait for a minimum of 32 clock cycles before negating PORESET.

The I/O power supply ramp-up slew rate should be slower than 4V/100

μs, this requirement is for ESD

circuit.

Figure 3 shows the power-up sequencing for switchable and continuous supplies.

Figure 3. Power-Up Sequencing

DDR signal1

GVDD = 2.5 V

DDR2 signal 1

GVDD = 1.8 V

DUART, system control, I2C, JTAG,SPI

NVDD = 3.3 V

GPIO signals

NVDD = 3.3 V

eTSEC

LVDD = 3.3 V / 2.5 V

1 Output Impedance can also be adjusted through configurable options in DDR Control Driver Register

(DDRCDR). See the

MPC8315E PowerQUICC II Pro Host Processor Reference Manual.

Table 3. Output Drive Capability (continued)

Driver Type

Output Impedance

(

Ω)

Supply

Voltage

Continuous I/O Voltage

Continuous Core Voltage

0.7 V

90%

Switchable I/O Voltage

Switchable Core Voltage (VDD)

0.7 V

90%

Power sequence for continuous power supplies

Power sequence for switchable power supplies

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