MSC7119 datasheet(42/60 Pages) FREESCALE

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MSC7119 Data Sheet, Rev. 8

Hardware Design Considerations

Freescale Semiconductor

3.2

Power Supply Design Considerations

This section outlines the MSC7119 power considerations: power supply, power sequencing, power planes, decoupling, power

supply filtering, and power consumption. It also presents a recommended power supply design and options for low-power

consumption. For information on AC/DC electrical specifications and thermal characteristics, refer to Section 2.

3.2.1

Power Supply

The MSC7119 requires four input voltages, as shown in Table 32.

You should supply the MSC7119 core voltage via a variable switching supply or regulator to allow for compatibility with

possible core voltage changes on future silicon revisions. The core voltage is supplied with 1.2 V (+5% and –10%) across VDDC

and GND and the I/O section is supplied with 3.3 V (± 10%) across VDDIO and GND. The memory and reference voltages supply

the DDR memory controller block. The memory voltage is supplied with 2.5 V across VDDM and GND. The reference voltage

is supplied across VREF and GND and must be between 0.49 × VDDM and 0.51 × VDDM. Refer to the JEDEC standard JESD8

(Stub Series Terminated Logic for 2.5 Volts (STTL_2)) for memory voltage supply requirements.

3.2.2

Power Sequencing

One consequence of multiple power supplies is that the voltage rails ramp up at different rates when power is initially applied.

The rates depend on the power supply, the type of load on each power supply, and the way different voltages are derived. It is

extremely important to observe the power up and power down sequences at the board level to avoid latch-up, forward biasing

of ESD devices, and excessive currents, which all lead to severe device damage.

Note:

There are five possible power-up/power-down sequence cases. The first four cases listed in the following sections are

recommended for new designs. The fifth case is not recommended for new designs and must be carefully evaluated

for current spike risks based on actual information for the specific application.

Table 32. MSC7119 Voltages

Voltage

Symbol

Value

Core

VDDC

1.2 V

Memory

VDDM

2.5 V

Reference

VREF

1.25 V

I/O

VDDIO

3.3 V

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