
Electrical, Mechanical, and Thermal Specification
6-1
AC Timing Specifications
6
A pin’s alternating-current (AC) characteristics include input and output capacitance. These factors
determine the loading for external drivers and other load analyses. The AC characteristics also
include a derating factor, which indicates how much the AC timings might vary with different
loads.
Note: The timing diagrams in this chapter show bursts that start at 0 and proceed to 3 or 7. However, the
least significant address (0) is not always received first during a burst transfer, because the Intel
PXA270 processor requests the critical word first during burst accesses.
Table 6-1 shows the AC operating conditions for the high- and low-strength input, output, and I/O
pins. All AC specification values are valid for the device’s entire temperature range.
6.1
AC Test Load Specifications
Figure 6-1 represents the timing reference load used in defining the relevant timing parameters of
the part. It is not intended to be either a precise representation of the typical system environment
nor a depiction of the actual load presented by a production tester. System designers use IBIS or
other simulation tools to correlate the timing reference load to system environment. Manufacturers
correlate to their production test conditions (generally a coaxial transmission line terminated at the
tester electronics).
Table 6-1. Standard Input, Output, and I/O-Pin AC Operating Conditions
Symbol
Description
Min
Typical
Max
Units
CIN
Input capacitance, all standard input and
I/O pins
—
10
pf
COUT_H
Output capacitance, all standard high-
strength output and I/O pins
20
—
50
pf
tdF_H
Output derating, falling edge on all
standard, high-strength output and I/O
pins, from 50-pf load.
—
TBD
—
ns/pf
tdR_H
Output derating, rising edge on all
standard, high-strength output and I/O
pins, from 50-pf load.
—
TBD
—
ns/pf
COUT_L
Output capacitance, all standard low-
strength output and I/O pins
20
—
50
pf
tdF_L
Output derating, falling edge on all
standard, low-strength output and I/O
pins, from 50-pf load.
—
TBD
—
ns/pf
tdR_L
Output derating, rising edge on all
standard, low-strength output and I/O
pins, from 50-pf load.
—
TBD
—
ns/pf