SN74BCT574 - Octal D-Type Flip-Flop 3-State | Texas Instruments
MPN: SN74BCT574 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.2 | $1.20 |
| 10 | $1.08 | $10.80 |
| 100 | $0.85 | $85.00 |
| 500 | $0.7 | $350.00 |
| 1,000 | $0.58 | $580.00 |
SN74BCT574 Overview
An octal D-type flip-flop is a digital logic register that stores eight bits of data, capturing the logic level present on each D input at the rising edge of a common clock and presenting it on the corresponding Q outputs. In the broader logic-IC hierarchy, it belongs to the flip-flop and register family of sequential logic, a core building block of microprocessor bus interfaces. Its 3-state outputs can be disabled via an active-low output-enable (OE) pin, allowing multiple devices to share a common data bus without contention.
Key features include the BiCMOS design that significantly reduces ICCZ (high-impedance supply current), full parallel access for loading all eight bits on one clock edge, and strong bipolar output drive for heavy capacitive bus loads. According to TI datasheet SCBS074C, the edge-triggered architecture guarantees that data is captured only on the rising clock edge, giving predictable setup and hold behavior in synchronous systems.
Technical depth: the BCT (BiCMOS) technology combines TTL-compatible input thresholds with bipolar totem-pole output stages, delivering low dynamic supply current at high clock frequencies and high output current capability, making it superior to pure CMOS ABT/ACT predecessors for heavily loaded 5 V buses.
Typical applications include buffer registers, I/O ports, bidirectional bus drivers, working registers in microprocessor systems, memory address/data latching, industrial control, and communication interfaces where reliable latching plus high bus drive are required.
Design tip: control OE properly to avoid bus contention (OE low enables outputs, high forces high-Z), decouple VCC close to the pins with 0.1 uF ceramic capacitors, and drive the clock with a clean edge to avoid metastability.
Drop-in alternatives for SN74BCT574 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SN74ACT574PWR
✅ Drop-In📋 Reference alternative (not in catalog)
CD74BCT574
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
SN54BCT574
✅ Drop-In📋 Reference alternative (not in catalog)
74BCT574D
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
74BCT574SC
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
SN74BCT574 Maximum Ratings & Electrical Characteristics
| Function | Octal D-type edge-triggered flip-flop with 3-state outputs |
| Logic Family | BCT (BiCMOS) |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Bits per Element | 8 |
| Trigger Type | Positive edge |
| Output Type | 3-state, TTL-compatible |
| Output Enable | Active-low OE pin |
| Technology Feature | State-of-the-art BiCMOS design significantly reduces ICCZ |
| Max Operating Voltage | 5.5 V |
| Packages | DB (SSOP-20), DW (SOIC-20), N (PDIP-20), NS (SOP-20) |
| Military Variant | SN54BCT574 (J or W package) |
| Mounting Type | Surface Mount (DB, DW, NS) / Through Hole (N) |
| Data Sheet | SCBS074C, September 1991, revised March 2003 |
SN74BCT574 Pin Configuration
| Pin 1 | OE — Output enable, active low (high = 3-state) |
| Pin 2 | D1 — Data input 1 |
| Pin 3 | D2 — Data input 2 |
| Pin 4 | D3 — Data input 3 |
| Pin 5 | D4 — Data input 4 |
| Pin 6 | D5 — Data input 5 |
| Pin 7 | D6 — Data input 6 |
| Pin 8 | D7 — Data input 7 |
| Pin 9 | D8 — Data input 8 |
| Pin 10 | GND — Ground |
| Pin 11 | CLK — Clock, positive-edge triggered |
| Pin 12 | Q8 — 3-state output 8 |
| Pin 13 | Q7 — 3-state output 7 |
| Pin 14 | Q6 — 3-state output 6 |
| Pin 15 | Q5 — 3-state output 5 |
| Pin 16 | Q4 — 3-state output 4 |
| Pin 17 | Q3 — 3-state output 3 |
| Pin 18 | Q2 — 3-state output 2 |
| Pin 19 | Q1 — 3-state output 1 |
| Pin 20 | VCC — Supply, 4.5 V to 5.5 V |
Typical Applications
SN74BCT574 is suitable for 6 applications: Microprocessor Bus Buffer Registers, Industrial Control Systems, Memory Address and Data Latching, Communication Interface Cards, Test and Measurement Instrumentation, I/O Ports and Bidirectional Bus Drivers.
Microprocessor Bus Buffer Registers
In 5 V microprocessor systems, the SN74BCT574 serves as a pipeline or working register that snapshots address or data bus states on each rising clock edge. Its BiCMOS output stage drives heavily loaded backplanes, and the 3-state outputs let it release the bus under OE control. Full parallel access of all eight bits on one clock edge simplifies timing analysis, with setup/hold margins documented in TI datasheet SCBS074C.
Recommended
Industrial Control Systems
Industrial PLC and motor-control I/O modules in legacy 5 V environments use the SN74BCT574 to latch sensor and actuator status words. The device tolerates the electrically noisy industrial environment thanks to TTL-compatible thresholds and strong bipolar drive, while the 3-state outputs allow one microcontroller bus to service many latched I/O banks via decoded OE signals. The PDIP (N) package option eases prototyping and field repair of through-hole control boards.
Recommended
Memory Address and Data Latching
When interfacing memory arrays that multiplex address and data, the SN74BCT574 captures the address or data word on a clock edge and holds it stable for the memory access window. Its BiCMOS drive sustains the capacitive loading of long address traces across PCB or backplane runs, and reduced ICCZ limits supply draw while outputs are disabled during the multiplexed phase of the bus cycle.
Recommended
Communication Interface Cards
Line cards and communication backplanes running at 5 V use the SN74BCT574 as status and control register banks between the protocol controller and the backplane connector. The positive-edge-triggered register gives deterministic capture timing relative to the system strobe, and the 3-state outputs share status lines among multiple cards. Strong output drive maintains signal integrity across backplane stubs and connector capacitance.
Recommended
Test and Measurement Instrumentation
Bench instruments and automated test equipment use the SN74BCT574 in capture registers that snapshot counter or sampler outputs synchronously with a trigger clock. The edge-triggered D architecture ensures all eight bits are captured simultaneously, eliminating skew that would occur with latching alternatives. PDIP packaging supports quick prototyping on breadboards, while SOIC-20 suits production ATE boards.
Recommended
I/O Ports and Bidirectional Bus Drivers
Parallel I/O expansion ports use the SN74BCT574 as an output port register: the CPU writes data on the clock edge and OE gates the port onto external cables or backplanes. Paired with a transceiver such as the SN74LVC244A or a bus switch, it forms a bidirectional port. The BiCMOS drive is particularly valuable for driving ribbon-cable capacitance in parallel-printer-style interfaces.
Recommended
Recommended Products Summary
Engineering reference data for SN74BCT574 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN74ACT574PWR | SN54BCT574 | 74BCT574D | 74BCT574SC |
|---|---|---|---|---|---|
| Package | DB/DW/N/NS (20-pin) | TSSOP-20 (PW) - different body, same '574 pin map | J or W (ceramic) | SOIC-20 (DW-compatible) | SOIC-20 (DW-compatible) |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | NXP Semiconductors | onsemi |
| Supply Voltage | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Technology | BiCMOS (BCT) | Advanced CMOS (ACT) | BiCMOS (BCT), military grade | BiCMOS (BCT) | BiCMOS (BCT) |
| Output Type | 3-state | 3-state | 3-state | 3-state | 3-state |
| Trigger | Positive edge | Positive edge | Positive edge | Positive edge | Positive edge |
| ICCZ (High-Z Supply Current) | Significantly reduced (BiCMOS) | Higher than BCT (CMOS leakage) | Same die as this product | Comparable BiCMOS spec | Comparable BiCMOS spec |
Key Differentiators
- BiCMOS drive for heavy bus loads (vs SN74ACT574PWR)
- Four package options (vs 74BCT574D)
- Military-grade companion (vs 74BCT574SC)
Design Notes
Bus contention is the most common failure mode with the SN74BCT574 in shared-bus systems. Because the bipolar output stage can source and sink substantial current, two devices driving opposite levels simultaneously cause large current flow. Decode OE so only one device is enabled per bus cycle, and add a pull-up or pull-down on OE to define the safe state (outputs off) during power-up and reset.
Drive the CLK pin with a clean, monotonic rising edge. Slow or noisy clock edges can cause multiple captures or metastability in the D flip-flops. If the clock source is a slow RC oscillator or a long, unterminated trace, buffer it through a Schmitt-trigger device such as SN74LVC1G14 before the CLK pin. Keep D-input setup and hold times satisfied per datasheet SCBS074C switching characteristics.
Place a 0.1 uF ceramic decoupling capacitor within 5 mm of the VCC pin (pin 20) and GND (pin 10). During simultaneous switching of all eight outputs into a capacitive bus, ground bounce can corrupt adjacent logic; use a solid ground plane and keep bus traces short. The DW (SOIC-20) package with a thermal pad-less layout dissipates little heat, so no thermal relief is needed at logic load levels.
Compliance Information
Compliance status varies by package suffix; check TI.com product page for the specific ordering part number. This is a legacy 5 V BiCMOS device first released September 1991 (SCBS074C).
