Logic frequently asked questions

LVC was the original name of the product line. In 1997 most of the parts had an "A" suffix added to the part name. There were several reasons for this:

1. Name change only due to Texas Instruments alternate source agreement.
2. Design changes that made propagation delay speeds faster.
3. Design changes to make 3-state bus interface part types 5-volt tolerant on outputs.

The following table summarizes the changes:

LVC Part Type	Name Change Only	Faster Speed	5V Tolerant I/O
00A		X
02A		X
04A		X
U4A	X
08A		X
10A	X
14A	X
32A		X
74A	X
86A		X
125A		X	X
138A	X
157A		X
240A		X	X
241A		X	X
244A		X	X
245A		X	X
257A		X	X
373A		X	X
374A		X	X
543A		X	X
544A		X	X
573A		X	X
574A		X	X
623A		X	X
646A		X	X
4245A		X
16244A			X
16245A			X

Note that the LVC652 has 5 volt-tolerant outputs but does not have an "A" suffix. This is the only exception for 3-state bus interface devices.

• LVC, LVT, and ALVT devices have 5V-tolerant inputs. The outputs of 3-state devices are also 5V-tolerant even at the low end of the V_CC range (for example, 1.2V for LVC) when the device is in 3-state.
• AHC has 5V tolerant inputs at V_CC = 2.0V to 3.6V.

Note that the LVC652 has 5V tolerant outputs but does not have an "A" suffix. This is the only exception for 3-state bus interface devices.

• Bus hold is available on 8-bit and 16-bit bus interface type of devices. It is not available on gates, counters, or other MSI functions.
• Bus hold is built in on the LVT, LVT16, and ALVT families.
• Bus hold is optional on the ABT16, LVC, LVC16, ALVC, and AVC families. For these families, bus hold is designated by adding an "H" to the name (e.g., ABTH16, LVCH, LVCH16, ALVCH, AND ALVH)
• ABT 8-bit devices do not have bus hold.

NOTE: Bus hold is available only on data pins, not on control pins.

Typically a resistor tied to V_CC or ground is needed to keep inputs from floating.

Certain ABT devices have an input disable circuit. De-asserting the output enable pin activates the circuit. This places the outputs in the high impedance mode and also disables the input circuitry, thereby allowing the inputs to float. Refer to the data sheet to determine which part types have this feature.

Most of the time the bus hold input will power up in the LOW state, but there is no guarantee for this.

• Bus interface functions for ABT, MB, LVT, and ALVT families support live insertion.
• LVC bus interface devices may be live inserted by connecting a pullup or pulldown resistor from the OE pin to V_CC or ground to disable the outputs during power-up or power-down.

LVC. Please also see our Product Cross Reference tool.

ALVC. Please also see our Product Cross Reference tool.

Yes. The corresponding NXP part number would be 74xxx2245 without the "R". The "R" in the part number indicates that there are output termination resistors on both sides of the part. NXP '2245 transceiver parts always have these resistors on both sides. When the other vendors' parts don't have the "R" in the part number, that indicates that termination resistors are only on one side. There is no NXP equivalent part number for this.

Ground the VCO input, pin 9, then pull up the external resistors R1 and R2 to V_CC. You can leave R3 open for the demodulator and pins 6 and 7 open for the external capacitor.