Texas Instruments SN74BCT757N

Overview

SN74BCT757N from Texas Instruments is an octal buffer/driver with open-collector outputs, designed for memory address driving and bus interfacing in 5-V TTL systems. It features complementary output-enable inputs (1OE and 2OE), noninverting logic, BiCMOS architecture, and supports 64 mA sink current per output at VCC = 4.5 V.

For engineers reviewing the SN74BCT757N datasheet, SN74BCT757N pinout, SN74BCT757N application, or SN74BCT757N equivalent, key selection criteria include open-collector drive capability, 20-pin PDIP package compatibility, 0°C to 70°C industrial temperature range, and TTL-level input thresholds with BiCMOS power efficiency.

Technical Context

The SN74BCT757N implements dual 4-bit noninverting buffers with independent active-low and active-high output-enable controls (1OE and 2OE), enabling flexible bus arbitration. Its BiCMOS design reduces quiescent supply current (ICCZ) versus pure bipolar implementations while maintaining TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2.0 V).

Each of the eight open-collector outputs can sink up to 64 mA at VOL ≤ 0.55 V (VCC = 4.5 V), supporting direct connection to 5-V buses or memory address lines. Propagation delays range from 2.4 ns (tPHL, A→Y) to 17.9 ns (tPLH, 2OE→Y) under CL = 50 pF loading.

Key Specifications

Pinout & Package

SN74BCT757N uses a 20-pin plastic dual in-line package (PDIP, N package), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is marked by a notch or dot; pin 10 is GND, pin 20 is VCC.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal open-collector buffer applications.

Compared with SN74LS244N and SN74ACT244N, the SN74BCT757N uniquely combines BiCMOS efficiency, dual OE control, and 64 mA drive - making it optimal for high-density memory addressing where both power and flexibility matter.

Availability

SN74BCT757N is available at Aetrix Electronics and suitable for memory address buffering, bus line driving, and clock distribution applications requiring stable component supply, long-term industrial availability, and through-hole assembly compatibility.

Supply support for SN74BCT757N includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74BCT757N belongs to TI's BCT (Bipolar-CMOS Transistor) logic family, engineered to deliver TTL-compatible performance with CMOS-like power efficiency for memory and bus interface applications.

FAQ

What is the maximum output sink current specification for SN74BCT757N?

The SN74BCT757N is rated for 64 mA per output when VCC = 4.5 V and VOL ≤ 0.55 V. This value is specified under recommended operating conditions and verified across the full 0°C to 70°C temperature range. The device maintains this drive strength without thermal derating in typical PCB layouts, making SN74BCT757N suitable for directly driving terminated bus lines or multiple TTL inputs.

Does SN74BCT757N support 3.3-V input logic levels?

No, SN74BCT757N does not guarantee reliable operation with 3.3-V logic inputs. Its input thresholds are TTL-specific: VIL = 0.8 V (max) and VIH = 2.0 V (min). A 3.3-V logic HIGH may fall below the required VIH margin depending on source impedance and noise, risking metastability. For mixed-voltage systems, SN74BCT757N should be driven only by 5-V TTL or LVTTL sources with appropriate level-shifting if needed.

What is the purpose of having both 1OE and 2OE inputs on SN74BCT757N?

The dual output-enable inputs (1OE active-low, 2OE active-high) on SN74BCT757N provide independent control over two groups of four outputs each. This allows selective activation of either the 1Y or 2Y output sets without affecting the other, enabling time-multiplexed bus access or hierarchical enable schemes. In SN74BCT757N, this architecture eliminates the need for external logic to manage group-wise gating in memory or peripheral interfaces.

Can SN74BCT757N be used in place of SN74LS244N without PCB changes?

No - although both are 20-pin PDIP octal buffers, SN74BCT757N has different pin assignments (e.g., 1OE/2OE placement, Y/A ordering) and open-collector outputs requiring external pull-ups, unlike the totem-pole outputs of SN74LS244N. Direct substitution would cause functional failure. SN74BCT757N is not a pin-compatible replacement for SN74LS244N; board redesign is required to accommodate its distinct pinout and drive topology.

What is the operating temperature range for SN74BCT757N?

SN74BCT757N is characterized for operation from 0°C to 70°C ambient temperature, meeting commercial and extended industrial requirements. This range is explicitly confirmed in the datasheet's "recommended operating conditions" table and validated across all electrical parameters including VOL, tPLH/tPHL, and ICC. It is not rated for automotive (−40°C to 125°C) or military temperature grades.