Logic selection guide 2016

LIVE INSERTION
What it does
Enables the installation or removal of a board while the
system is powered up.
System part
powering
up/down
Low
flow into the inputs and outputs of an unpowered
device ensures that, when the device is inserted, the
effective load seen on a powered data bus is minimal.
Upon detection of the inserted board, the output enable
input should be used to prevent data contention on the
backplane. Devices that include power-up 3-state allow
more time for the inserted board to be detected and the
state of the output enable pin to be set.
Live insertion
Why it’s important
Active
system
part
High
Live insertion, which is also known as hot swapping or
hot plugging, involves inserting or extracting a board
without switching off the power. That minimizes down
time, and makes it easier to repair or upgrade a system.
The goal is to maintain data integrity on the system
bus while preventing damage to components on the
host system or on the inserted/extracted card. Various
Bus
degrees of bus isolation makes this possible.
Live insertion with I OFF
and 3-state outputs
This feature, listed in datasheets as I PU
/I PD
or I OZPU
/I OZPD
,
supports the same power-down mode as I OFF
, but adds
the ability to keep outputs 3-stated during power-up
and power-down. This prevents outputs from turning
on before reaching the V CC
trip point, as shown in the
figure. 3-state power-up mode also prevents the bus
from loading at power-up. The 3-state power-up feature
is available on NXP’s low-voltage LVT and ALVT families
(the outputs 3-state below V CC
= 1.2 V), and on the 5 V
ABT family (the outputs 3-state below V CC
= 2 V).
OE follows V CC
, ensuring device remains in 3-state
(Z) during power-up/down
V cc
Where you’ll find it
3.3 V
Every NXP logic family supports some level of bus
1.2 V
isolation, but live insertion is enabled by using one of
three features: I OFF
on its own, I OFF
with 3-state outputs,
or I OFF
, 3-state outputs and the BIAS V pin.
Output
Off (Z)
On
Off (Z)
Live insertion with I OFF
The I OFF
feature, which is described later in this chapter,
supports partial power-down mode. Preventing current
Power-up mode with 3-state outputs
5 V 3.3 V 2.5 V 1.8 V 1.2 V 0.8 V
Live insertion with I OFF
LVC Mini
Logic
LVC, AVC(M),
AUP
LVC, ALVC,
AVC(M), AUP,
AXP
LVC, ALVC,
AVC(M), AUP,
AXP
AVC(M), AUP,
AXP
AXP
Live insertion with I OFF
and 3-state
outputs
LVT, ALVT
NXP Logic selection guide 2016
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