Logic selection guide 2016

SOURCE TERMINATION
What it does
Improves impedance matching in distributed systems
and eliminates the need for external termination
resistors.
R s Z L
V IN
V SIG
Buffer driving a source-terminated distributed load
Where you’ll find it
Source-termination options are available in the lowvoltage
BiCMOS families (LVT and ALVT) and the lowvoltage
CMOS families [LVC, ALVC, AVC(M)]. Many of
NXP’s 8-, 16-, and 32-bit products – including buffers,
inverters, drivers, flip-flops, latches/registered drivers,
and transceivers – have source-termination options. In
transceivers, source termination is included on all I/O
ports.
A “2” is used to identify device types that include source
termination (e.g. 74LVT2244 & 74LVC162244).
Source-termination resistor
Why it’s important
Source termination is commonly used to terminate
distributed systems so as to avoid issues with signal
integrity. The output resistance of the driver is matched
to the characteristic impedance of the distributed system
using an external resistor. Integrated source termination
solves signal-integrity issues associated with distributed
systems without the need of external components, and
thus reduces BOM and cost.
Sourcetermination
resistors
3.3 V 2.5 V 1.8 V 1.2 V
LVC,
ALVC,
LVT,
ALVT,
AVC(M)
LVC,
ALVC,
ALVT,
AVC(M)
LVC,
ALVC,
AVC(M)
AVC(M)
NXP Logic selection guide 2016
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