IMX28CEC datasheet(21/70 Pages) FREESCALE

21 / 70 page

i.MX28 Applications Processors Data Sheet for Consumer Products, Rev. 1

Freescale Semiconductor

Table 25 shows the external devices supported by the EMI.

3.3.2

GPIO I/O DC Parameters

Max load includes capacitive load due to PCB traces, pad capacitance and driver self-loading. For the

internal pull up setting of each pad, see the “Pin Control and GPIO” section of the reference manual.

Table 26 shows the digital pin DC characteristics for GPIO in 3.3-V mode. Measurements are valid for

eight pins loaded using the 4mA driver, four pins loaded using the 8mA driver, and two pins loaded using

either the 12mA or 16mA driver.

1.8

DDR2/mDDR

Low

TBD

Medium

TBD

High

TBD

Table 25. External Devices Supported by the EMI

DRAM Device

Max Load1, 2

1 Max load includes capacitive load due to PCB traces, pad capacitance and driver self-loading.

2 Setting is for worst case. Freescale’s EMI interface uses less powerful drivers than those typically used in mDDR devices. A

possible transmission-line effect on the PC board must be suppressed by minimizing the trace length combined with

Freescale’s slower edge-rate drivers. The i.MX28 provides up to 16 mA programmable drive strength. However, the 16-mA

mode is an experimental mode. With the 16-mA mode, the EMI function may be impaired by Simultaneous Switching Output

(SSO) noise. In general, the stronger the driver mode, the noisier the on-chip power supply. Freescale recommends not using

a stronger driver mode than is required. Because on-chip power and ground noise is proportional to the inductance of its return

path, users should make their best effort to reduce inductance between the EMI power and ground balls and the PC board

power and ground planes.

Pad Voltage

DDR2

15 pF

1.8 V

mDDR

15 pF

1.8 V

LVDDR2

15 pF

1.5 V

Table 26. Digital Pin DC Characteristics for GPIO in 3.3-V Mode

Parameter

Symbol

Min

Max

Units

Input voltage high (dc)

VIH

VDDIO

Input voltage low (dc)

VIL

—

0.8

Output voltage high (dc)

VOH

0.8

× VDDIO

—

Output voltage low (dc)

VOL

—

0.4

Output source current1 (dc)

gpio

IOH – Low

-5.0

—

IOH – Medium

-9.5

—

IOH – High

-11.4

—

Table 24. ON Impedance of EMI Drivers for Different Drive Strengths (continued)

Mode

Drive

Min. (

Ω)Typ. (Ω)Max. (Ω)

IMX28CEC Datasheet(PDF) 21 Page - Freescale Semiconductor, Inc

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