Texas Instruments SN74BCT29821DW

Overview

SN74BCT29821DW from Texas Instruments is a 10-bit edge-triggered D-type bus-interface flip-flop with 3-state outputs, designed for driving high-capacitance or low-impedance bus lines. It operates at 5 V supply, supports 125 MHz clock frequency, features ±24 mA output drive, and functions across 0°C to 70°C ambient temperature - ideal for I/O port buffering and bidirectional bus interfacing in industrial control systems.

For engineers reviewing the SN74BCT29821DW datasheet, SN74BCT29821DW pinout, SN74BCT29821DW application, or SN74BCT29821DW equivalent, key selection considerations include its BiCMOS-based low ICCZ quiescent current, OE-controlled high-impedance outputs, and precise timing parameters (tsu = 7 ns, th = 1 ns) critical for synchronous bus arbitration and register staging.

Technical Context

This device implements ten independent D-type flip-flops synchronized to the rising edge of CLK, with all outputs sharing a common buffered output-enable (OE) signal. Its BiCMOS architecture enables fast switching (tPLH/tPHL ≤ 10 ns) while maintaining low static power consumption (ICCZ ≤ 6 mA).

The 3-state outputs support direct bus connection without pull-up components, and OE operation is transparent to internal flip-flop state retention - new data may be latched or old data held regardless of OE logic level. Output voltage levels meet TTL-compatible thresholds (VIH = 2 V, VIL = 0.8 V) under 4.5–5.5 V VCC.

Key Specifications

Pinout & Package

SN74BCT29821DW is housed in a 24-pin SOIC (DW) package with 300-mil body width and gull-wing leads, compliant with JEDEC MS-013AC. Pin 1 is OE (active-low output enable), pins 2–11 are data inputs (1D–10D), pin 13 is CLK, pins 14–23 are outputs (1Q–10Q), pin 24 is VCC, and pin 12 is GND.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 10-bit bus-interface flip-flop applications.

Compared with SN74BCT29821DW, SN74ACT29821DW trades drive strength for lower static power and better noise rejection, while SN74LS29821N sacrifices speed and efficiency to maintain full TTL compatibility - making SN74BCT29821DW the optimal balance for new 5 V bus-interface designs requiring both speed and drive.

Availability

SN74BCT29821DW is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy bus interface adapters, and memory-mapped peripheral register implementations requiring stable component supply and long-term production continuity.

Supply support for SN74BCT29821DW 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 founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74BCT29821DW belongs to TI's BCT (Bipolar-CMOS Transistor) logic family, engineered specifically for high-speed, low-power bus interface and register applications in 5 V systems.

FAQ

What is the maximum clock frequency supported by the SN74BCT29821DW?

The SN74BCT29821DW supports a maximum clock frequency of 125 MHz under recommended operating conditions (VCC = 5 V, TA = 25°C). This rating is validated across the full commercial temperature range (0°C to 70°C) and assumes CL = 50 pF load. At 125 MHz, the device maintains guaranteed setup (7 ns) and hold (1 ns) times, enabling reliable synchronization in high-speed bus architectures. The SN74BCT29821DW achieves this performance through its BiCMOS design, which combines bipolar speed with CMOS low-power characteristics.

Does the SN74BCT29821DW support hot insertion or live bus connection?

The SN74BCT29821DW is not explicitly rated for hot insertion per JEDEC standards, but its absolute maximum ratings support safe operation during live bus connection: outputs tolerate −0.5 V to 5.5 V in disabled state, and input clamp current is rated to −18 mA. When OE is asserted high before power-up, all outputs remain in high-impedance, preventing bus contention. However, TI does not guarantee glitch-free behavior during partial power sequencing, so controlled power-rail ramping and OE initialization are recommended. The SN74BCT29821DW should be used with external series resistors or bus isolation if true hot-swap capability is required.

How does the output-enable (OE) function interact with internal flip-flop state in the SN74BCT29821DW?

In the SN74BCT29821DW, the output-enable (OE) signal affects only the output drivers - it has no effect on internal flip-flop operation or stored data. While OE is high (disabled), the Q outputs enter high-impedance, but the latched data remains intact and can be updated on subsequent CLK edges. This allows continuous data capture or retention independent of bus activity, enabling seamless handoff between multiple bus masters. The SN74BCT29821DW thus supports concurrent register update and bus arbitration without risk of data loss or metastability.

What is the purpose of the BiCMOS design in the SN74BCT29821DW?

The BiCMOS design in the SN74BCT29821DW integrates bipolar transistors for high-speed switching with CMOS circuitry for low static power consumption. This hybrid architecture delivers 125 MHz operation while limiting ICCZ (quiescent supply current with outputs open) to just 2–6 mA - significantly lower than pure bipolar alternatives like the SN74LS29821N (ICC ≈ 45 mA). The result is reduced thermal load and improved power efficiency in dense PCB layouts. The SN74BCT29821DW leverages this advantage for sustained high-speed bus interfacing without excessive heat dissipation.

Can the SN74BCT29821DW drive a 50 pF bus load while meeting timing specifications?

Yes, the SN74BCT29821DW is characterized for CL = 50 pF in its switching characteristics table, with tPLH/tPHL ≤ 10 ns and tPZH/tPZL ≤ 12 ns at VCC = 5 V and TA = 25°C. Its ±24 mA high-level and 48 mA low-level output drive ensures clean signal transitions into 50 pF loads, including trace capacitance and receiver inputs. The SN74BCT29821DW maintains these specs across the full 0°C to 70°C range, making it suitable for board-level bus routing without added termination or buffering - provided VCC regulation stays within 4.5–5.5 V.