PCIMX258CJM4A datasheet(16/144 Pages) FREESCALE

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i.MX25 Applications Processor for Consumer and Industrial Products, Rev. 3

Freescale Semiconductor

3.2

Supply Power-Up/Power-Down Requirements and Restrictions

Any i.MX25 board design must comply with the power-up and power-down sequence guidelines given in

this section to ensure reliable operation of the device. Recommended power-up and power-down

sequences are given in the following subsections.

CAUTION

Deviations from the guidelines in this section may result in the following

situations:

•

Excessive current during power-up phase

•

Prevention of the device from booting

•

Irreversible damage to the i.MX25 (worst-case scenario)

NOTE

For security applications, the coin battery must be connected during both

power-up and power-down sequences to ensure that security keys are not

unintentionally erased.

3.2.1

Power-Up Sequence

The following power-up sequence is recommended:

1. Assert power on reset (POR).

2. Turn on digital logic domain and I/O power supplies VDDn and NVCCx.

3. Turn on all other analog power supplies, including USBPHY1_VDDA_BIAS,

USBPHY1_UPLL_VDD, USBPHY1_VDDA, USBPHY2_VDD, OSC24M_VDD,

MPPLL_VDD, UPLL_VDD, NVCC_ADC, and FUSEVDD (FUSEVDD is tied to GND if fuses

are not being programmed). The minimum time between turning on each power supply is the time

it takes for the previous supply to be stable.

4. Negate the POR signal.

NOTE

•

The user is advised to connect FUSEVDD to GND except when fuses

are being programmed, in order to prevent unintentional blowing of

fuses.

•

Other power-up sequences may be possible; however, the above

sequence has been verified and is recommended.

•

There is a 1-ms minimum time between supplies coming up, and a 1-ms

minimum time between POR_B assert and deassert.

PCIMX258CJM4A Datasheet(PDF) 16 Page - Freescale Semiconductor, Inc

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