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Texas Instruments SN74LS640N3 — Logic ICs

SN74LS640N3 Bus Transceiver, Inverting, 20-DIP, 15mA/24mA

MPNSN74LS640N3
End of Life

Texas Instruments 74LS series, SN74LS640N3, Bus Transceiver, Inverting, 3-State, Through Hole, 20-DIP (0.300", 7.62mm), 4.75V–5.25V supply, 0°C to 70°C.

$0.41Ref. price · indicative, final on quote
Texas Instruments SN74LS640N3 datasheet (PDF)
Packaging20-DIP (0.300", 7.62mm)
RoHSRoHS non-compliant
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Aug 2026

Specifications

SN74LS640N3 specifications
ParameterValue
Logic typeTransceiver, Inverting
Output type3-State
MountingThrough Hole
Supply voltage4.75V ~ 5.25V
Current - output high, low15mA, 24mA
Operating temperature0°C ~ 70°C (TA)
PackageBulk
Case20-DIP (0.300\", 7.62mm)
Number of elements1
Number of bits per element8

Product details

Inverting bus transceiver for 5 V TTL backplanes

The SN74LS640N3: Its 3-state outputs let multiple transceivers share the same bus lines without contention. The inverting logic (data on the A bus appears inverted on the B bus) is a deliberate choice for active-low control schemes or when the bus polarity must be flipped.

The SN74LS640N3 can source 15 mA and sink 24 mA per output. The 3-state control (active-low output enable) lets you disconnect the transceiver from the bus when another device is driving.

Package and retrofit fit

Housed in a 20-pin DIP with 0.300-inch row spacing, the SN74LS640N3 is a direct drop-in for sockets or wave-solder holes on legacy PCBs. The through-hole mounting means no reflow profile changes — just hand-solder or wave-solder it in.

This is important for long-life equipment that needs a guaranteed supply of spare parts.

Frequently asked questions

Where can I buy SN74LS640N3?

Submit a request for quote and we will confirm availability and current pricing at quote time.

What is the difference between SN74LS640 and SN74LS245?

The SN74LS640 is an inverting transceiver — data on the A bus appears inverted on the B bus. The SN74LS245 is non-inverting. Both are 8-bit, 3-state, 20-pin DIP parts with the same pinout; the choice depends on whether your bus needs polarity inversion.

What is the equivalent of SN74LS640N3?

The closest functional alternative is the SN74LS645-1N, which is also an 8-bit transceiver in the same 20-pin DIP package but non-inverting. If bus polarity is not a constraint, it is a drop-in replacement for dual-sourcing.