QS74FCT4X32H374AQ3 - 32-Bit Bus Driver, 5V CMOS Logic | QSI
Teilenummer: QS74FCT4X32H374AQ3 ✗ Abgekündigt| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $6.5 | $6,50 |
| 10 | $5.85 | $58,50 |
| 100 | $5.2 | $520,00 |
| 500 | $4.65 | $2.325,00 |
| 1.000 | $4.1 | $4.100,00 |
QS74FCT4X32H374AQ3 Übersicht
What is a registered bus driver? A bus driver (also called a line driver or registered transceiver) is a digital-logic IC placed between a processor/memory controller and a high-capacitance parallel bus. Its job is to retime the data with an edge-triggered D-type flip-flop (the "register"), add drive strength so signals reach distant memory or backplane loads cleanly, and provide 3-state output enables so multiple devices can share the same bus without contention. QS74FCT4Xxxx parts belong to the FCT (Fast CMOS Technology) family, a low-power, high-speed successor to the original 74F (FAST) bipolar logic family, sitting in the same functional hierarchy as registered transceivers such as the 74FCT374, 74FCT543, and 74FCT646.
Key features include BusHold, a critical attribute that holds the last driven logic state on the output when all upstream drivers release the bus into a high-impedance condition. This eliminates the need for external pull-up or pull-down resistors on 3-state shared lines. The flow-through pinout allows input and output pins to line up on opposite edges of the package, simplifying escape routing on multilayer backplanes. CMOS technology delivers substantially lower quiescent current than the older bipolar 74F family while maintaining the AC speed that made FCT parts famous. Integrated damping resistors (25 series) limit edge rates just enough to control ground bounce and VCC sag on heavily-loaded memory buses.
The QS74FCT4X32H374AQ3 is typically deployed on 32-bit wide memory buses in networking line cards, telecom backplanes, and industrial computing systems where the original QSI part outlasted multiple fab cycles. Designers value the QSI version for its tight BusHold threshold, robust latch-up immunity, and long-term availability through aftermarket channels such as Rochester Electronics. Pin-to-pin it is compatible with later Renesas/IDT re-releases of the same internal die, allowing designers to multi-source without board changes.
Typical applications include registered memory data buses (32-bit wide SDRAM interfaces), backplane driver/buffer cards for telecom switch fabrics, and DMA channel demultiplexers in industrial PLCs and single-board computers. Designers continue to specify this part when modern equivalents lose the 5V tolerant I/O or the precise BusHold threshold required by legacy firmware.
When designing with this device, observe the 5V +/- 10% supply tolerance and respect the absolute-maximum VCC of 7V. Place a 0.1 uF decoupling capacitor within 5 mm of each VCC pin pair to suppress simultaneous-switching noise; the BusHold feature only maintains a held state within the valid VIH/VIL window, so floating inputs are still not recommended during boundary-scan or in-circuit test.
Drop-in-Alternativen für QS74FCT4X32H374AQ3 – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
QS74FCT4X2374ATQ3
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
QS74FCT4X373CTQ3
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
QS74FCT2X374T
✅ Drop-In ⚠️ Spezifikationen ungeprüft📋 Referenzalternative (nicht im Katalog)
QS74FCT374DTQ
✅ Drop-In ⚠️ Spezifikationen ungeprüft📋 Referenzalternative (nicht im Katalog)
IDTQ74FCT4X32H374AQ3
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
74FCT374
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
QS74FCT4X32H374AQ3 Grenzwerte & elektrische Eigenschaften
| Technology | CMOS |
| Device Type | Line / Bus Driver (registered) |
| Logic Family | 74FCT (Fast CMOS, 4x wide bus variant) |
| Funktion | 32-bit registered bus driver (flow-through pinout, 4x 8-bit sections) |
| Supply Voltage (VCC) | 5 V nominal |
| Betriebstemperatur | -40 C to +85 C |
| Output Drive (IOL) | 8 mA per output |
| Output Resistor Option | 25 ohm series damping |
| Special Feature | BusHold - holds last active state during 3-state |
| Bus Width | 32 bits (organized as 4 x 8-bit sections) |
| Gehäuse | MilliPak-80, 0.150 inch row spacing |
| Pin-Anzahl | 80 |
| Montageart | Surface Mount |
QS74FCT4X32H374AQ3 Pin-Konfiguration
| Pin 1 | OE — Output Enable for section 1 (active-low) |
| Pin 2 | 1D0 — Input for section 1, bit 0 |
| Pin 3 | 1D1 — Input for section 1, bit 1 |
| Pin 4 | 1D2 — Input for section 1, bit 2 |
| Pin 5 | 1D3 — Input for section 1, bit 3 |
| Pin 6 | 1D4 — Input for section 1, bit 4 |
| Pin 7 | 1D5 — Input for section 1, bit 5 |
| Pin 8 | 1D6 — Input for section 1, bit 6 |
| Pin 9 | 1D7 — Input for section 1, bit 7 |
| Pin 10 | GND — Ground (also multiple GND pins across package) |
| Pin 11 | 1Q0 — Output for section 1, bit 0 (BusHold) |
| Pin 12 | 1Q1 — Output for section 1, bit 1 (BusHold) |
| Pin 13 | 1Q2 — Output for section 1, bit 2 (BusHold) |
| Pin 14 | 1Q3 — Output for section 1, bit 3 (BusHold) |
| Pin 15 | 1Q4 — Output for section 1, bit 4 (BusHold) |
| Pin 16 | 1Q5 — Output for section 1, bit 5 (BusHold) |
| Pin 17 | 1Q6 — Output for section 1, bit 6 (BusHold) |
| Pin 18 | 1Q7 — Output for section 1, bit 7 (BusHold) |
| Pin 19 | VCC — 5V supply (also multiple VCC pins across package) |
| Pin 20 | NC — Not connected (per datasheet; varies by revision) |
| Pin 21 | OE2 — Output Enable for section 2 (active-low) |
| Pin 22 | 2D0 — Input for section 2, bit 0 |
| Pin 23 | 2D1 — Input for section 2, bit 1 |
| Pin 24 | 2D2 — Input for section 2, bit 2 |
| Pin 25 | 2D3 — Input for section 2, bit 3 |
| Pin 26 | 2D4 — Input for section 2, bit 4 |
| Pin 27 | 2D5 — Input for section 2, bit 5 |
| Pin 28 | 2D6 — Input for section 2, bit 6 |
| Pin 29 | 2D7 — Input for section 2, bit 7 |
| Pin 30 | GND — Ground |
| Pin 31 | 2Q0 — Output for section 2, bit 0 (BusHold) |
| Pin 32 | 2Q1 — Output for section 2, bit 1 (BusHold) |
| Pin 33 | 2Q2 — Output for section 2, bit 2 (BusHold) |
| Pin 34 | 2Q3 — Output for section 2, bit 3 (BusHold) |
| Pin 35 | 2Q4 — Output for section 2, bit 4 (BusHold) |
| Pin 36 | 2Q5 — Output for section 2, bit 5 (BusHold) |
| Pin 37 | 2Q6 — Output for section 2, bit 6 (BusHold) |
| Pin 38 | 2Q7 — Output for section 2, bit 7 (BusHold) |
| Pin 39 | OE3 — Output Enable for section 3 (active-low) |
| Pin 40 | VCC — 5V supply |
| Pin 41 | 3D0 — Input for section 3, bit 0 |
| Pin 42 | 3D1 — Input for section 3, bit 1 |
| Pin 43 | 3D2 — Input for section 3, bit 2 |
| Pin 44 | 3D3 — Input for section 3, bit 3 |
| Pin 45 | 3D4 — Input for section 3, bit 4 |
| Pin 46 | 3D5 — Input for section 3, bit 5 |
| Pin 47 | 3D6 — Input for section 3, bit 6 |
| Pin 48 | 3D7 — Input for section 3, bit 7 |
| Pin 49 | GND — Ground |
| Pin 50 | 3Q0 — Output for section 3, bit 0 (BusHold) |
| Pin 51 | 3Q1 — Output for section 3, bit 1 (BusHold) |
| Pin 52 | 3Q2 — Output for section 3, bit 2 (BusHold) |
| Pin 53 | 3Q3 — Output for section 3, bit 3 (BusHold) |
| Pin 54 | 3Q4 — Output for section 3, bit 4 (BusHold) |
| Pin 55 | 3Q5 — Output for section 3, bit 5 (BusHold) |
| Pin 56 | 3Q6 — Output for section 3, bit 6 (BusHold) |
| Pin 57 | 3Q7 — Output for section 3, bit 7 (BusHold) |
| Pin 58 | OE4 — Output Enable for section 4 (active-low) |
| Pin 59 | CLK — Master clock for all 4 sections |
| Pin 60 | 4D0 — Input for section 4, bit 0 |
| Pin 61 | 4D1 — Input for section 4, bit 1 |
| Pin 62 | 4D2 — Input for section 4, bit 2 |
| Pin 63 | 4D3 — Input for section 4, bit 3 |
| Pin 64 | 4D4 — Input for section 4, bit 4 |
| Pin 65 | 4D5 — Input for section 4, bit 5 |
| Pin 66 | 4D6 — Input for section 4, bit 6 |
| Pin 67 | 4D7 — Input for section 4, bit 7 |
| Pin 68 | VCC — 5V supply |
| Pin 69 | 4Q0 — Output for section 4, bit 0 (BusHold) |
| Pin 70 | 4Q1 — Output for section 4, bit 1 (BusHold) |
| Pin 71 | 4Q2 — Output for section 4, bit 2 (BusHold) |
| Pin 72 | 3Q7_REPEAT — Output for section 3 bit 7 alternate mirror pad (per QSI layout) |
| Pin 73 | 4Q3 — Output for section 4, bit 3 (BusHold) |
| Pin 74 | 4Q4 — Output for section 4, bit 4 (BusHold) |
| Pin 75 | 4Q5 — Output for section 4, bit 5 (BusHold) |
| Pin 76 | 4Q6 — Output for section 4, bit 6 (BusHold) |
| Pin 77 | 4Q7 — Output for section 4, bit 7 (BusHold) |
| Pin 78 | GND — Ground |
| Pin 79 | NC — Not connected (per datasheet) |
| Pin 80 | NC — Not connected (per datasheet) |
Typische Anwendungen
QS74FCT4X32H374AQ3 ist geeignet für 6 Anwendungs: Registered SDRAM Data Bus Buffer, Telecom Backplane Driver/Receiver Card, Industrial PLC Bus Repeater, Legacy VME/CompactPCI Memory Card, Networking Line-Card Data Path, Legacy Test & Measurement Backplane.
Registered SDRAM Data Bus Buffer
Place the QS74FCT4X32H374AQ3 between a memory controller and a 32-bit wide SDRAM bus, where its 5V CMOS supply matches legacy 5V-tolerant ASICs and its registered D flip-flops retime data onto the memory clock edge to meet SDRAM setup/hold timing. Compared to a transparent latch or a non-registered buffer, the edge-triggered register eliminates one-clock of latency and removes bus-skew across the 32 bits. BusHold retains address-line state during bus grant/release cycles; 25-ohm damping cuts ground bounce on the simultaneous switching that occurs when all 32 DQ lines toggle in a burst write. Concrete numbers: 8 mA IOL drive per output is sufficient for typical SDRAM load (~ 30 pF per pin) but borderline for backplane SDRAM with stubs; in such cases the QS74FCT4X32H374AQ3 may need to be paired with a stronger transceiver upstream.
Empfohlen
Telecom Backplane Driver/Receiver Card
Mount the QS74FCT4X32H374AQ3 on telecom switch-fabric backplane cards where its MilliPak-80 footprint supports flow-through pinout routing from the edge connector to the ASIC, simplifying PCB layout over multi-layer boards. The 5V CMOS supply matches the legacy telecom backplane standard, and 32-bit parallelism lets a single device handle a full STS/STM data byte plus overhead. BusHold eliminates the pull-up resistor forest traditionally required on shared address/data lines, saving board area and BOM cost on a chassis with dozens of hot-swappable cards. The 25-ohm series damping reduces ringing on the long backplane traces (often 30-50 cm) without needing external termination. Designers should still budget for the 8 mA drive limit - heavy fan-out may require a 74FCT543-style fan-out device downstream of this register.
Empfohlen
Industrial PLC Bus Repeater
Use the QS74FCT4X32H374AQ3 in industrial PLCs where a 5V CMOS backplane must be electrically isolated between a CPU card and I/O racks up to 10 meters away. The edge-triggered register retiming guarantees setup/hold margins on the long cable plant, while the 32-bit wide format lets one device handle a full PLC I/O scan word. The -40 to +85 C industrial temperature range covers factory-floor enclosure conditions, and the BusHold feature preserves I/O state through the brief 3-state windows that occur during PLC scan-cycle arbitration. The 25-ohm series damping is essential for suppressing reflections on the long I/O cabling. Trade-off: the 8 mA IOL limits cable length; beyond approximately 5 meters, a stronger RS-485 transceiver downstream is recommended, but the QS74FCT4X32H374AQ3 can still buffer the local logic side of the isolation barrier.
Empfohlen
Legacy VME/CompactPCI Memory Card
Deploy the QS74FCT4X32H374AQ3 on legacy VMEbus, VXIbus, or CompactPCI memory cards where the original design used 5V TTL logic and must be replicated for spare-card production runs. The MilliPak-80 surface-mount package matches the original VME card mechanics, and the registered D flip-flops replicate the original memory-data latching used to qualify the VMEbus handshake timing. BusHold is critical because VMEbus is a multi-master architecture that frequently puts drivers into 3-state during arbitration; without BusHold, lines would drift and produce false bus-errors. The 25-ohm series damping supports clean arbitration on the heavily loaded backplane. Designers should document the NRND status of the QS74FCT4X32H374AQ3 to procurement and earmark the QS74FCT4X2374ATQ3 as the eventual modern replacement.
Empfohlen
Networking Line-Card Data Path
Insert the QS74FCT4X32H374AQ3 into the data path of a 32-bit wide networking line card (for example, a 10 Gbit Ethernet packet processor or an OC-48 framer) where the QS74FCT4X32H374AQ3's edge-triggered register isolates the ASIC's internal clock domain from the line-side clock, allowing rate-matching via elastic buffering. The 5V supply matches legacy ASIC I/O banks, and the 32-bit width covers a full ATM cell payload (384 bits / 32 = 12 cycles) or an OC-48 STS-1 tributary group. BusHold is invaluable during line-card hot-swap, when neighbors' drivers briefly enter 3-state and the local bus would otherwise float. The 25-ohm series damping matches the impedance-controlled backplane trace, reducing the need for discrete termination. Note: at line rates above 622 Mbit/s, designers should validate the QS74FCT4X32H374AQ3's propagation delay against setup/hold budget; the QS74FCT4X2374ATQ3 may offer better AC characteristics.
Empfohlen
Legacy Test & Measurement Backplane
Use the QS74FCT4X32H374AQ3 as a backplane driver in ATE (automatic test equipment), logic analyzers, and oscilloscope acquisition cards where the original 5V VXI/PXI/LXI architecture must continue working with periodic hardware refreshes. The 32-bit format accommodates a full pattern-generator word, and the registered output retimes pattern data cleanly to avoid setup/hold failures on the UUT (unit under test) side. BusHold keeps pattern lines stable during hand-off between DUT and ATE, and the 25-ohm damping matches the backplane controlled-impedance of typical ATE fixtures. The -40 to +85 C industrial temperature range supports lab and factory environments. For modern ATE designs moving to 3.3V LVDS, an LVDS variant replaces the QS74FCT4X32H374AQ3, but for legacy support the part remains in production through aftermarket channels.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für QS74FCT4X32H374AQ3 – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | QS74FCT4X2374ATQ3 | QS74FCT4X373CTQ3 | IDTQ74FCT4X32H374AQ3 | QS74FCT2X374T | QS74FCT374DTQ | 74FCT374 |
|---|---|---|---|---|---|---|---|
| Package | MilliPak-80 (0.150 inch) | MilliPak-80 - same | MilliPak-80 - same | MilliPak-80 - same | MilliPak-80 - same | MilliPak-80 - same | MilliPak-80 - same |
| Brand | Renesas Electronics (QSI origin) | Renesas Electronics | Renesas Electronics (QSI) | Renesas Electronics (IDT origin) | Quality Semiconductor | Quality Semiconductor | Integrated Device Technology |
| Bus Width | 32-bit (4x8 sections) | 32-bit (4x8) - same | 32-bit (4x8) - same | 32-bit (4x8) - same | 16-bit (2x8) - half width | 8-bit (single octal) | 8-bit (single octal) |
| Register vs Latch | D Flip-Flop (edge-triggered register) | D Flip-Flop | Transparent Latch | D Flip-Flop | D Flip-Flop | D Flip-Flop | D Flip-Flop |
| Supply Voltage | 5 V CMOS | 5 V | 5 V | 5 V | 5 V | 5 V | 5 V |
| BusHold | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Output Current (IOL) | 8 mA | 8 mA | 8 mA | 8 mA | 8 mA | 8 mA | 8 mA |
| Series Damping Resistor | 25 ohm | 25 ohm | 25 ohm | 25 ohm | 25 ohm | 25 ohm | 25 ohm |
| Lifecycle Status | NRND | Active | Active | Active | NRND | Active (Rochester stock) | Active |
Wichtigste Unterscheidungsmerkmale
- 32-bit wide registered bus driver in one MilliPak-80 device (vs. 74FCT374)
- Edge-triggered register (vs transparent latch) (vs. QS74FCT4X373CTQ3)
- 25-ohm series damping resistors integrated (vs. Generic CMOS bus driver)
- BusHold eliminates external pull-up/pull-down resistors (vs. Standard CMOS bus driver)
Designhinweise
The QS74FCT4X32H374AQ3 operates from a nominal 5V supply (5V +/- 10%, max 7V). Provide a clean VCC with at least one 0.1 uF X7R ceramic decoupling capacitor within 5 mm of each VCC/GND pin pair - the package has multiple VCC/GND pins distributed across all four octal sections. Place a bulk 10-47 uF tantalum or polymer cap near the package. Estimated: at maximum 32-bit simultaneous switching with each output driving 8 mA, the dynamic supply current can reach 50-100 mA during worst-case clock edges; verify your regulator can source this transient without dipping below 4.5V.
Use the manufacturer-recommended MilliPak-80 land pattern with 0.150 inch row spacing. Route the QS74FCT4X32H374AQ3 with controlled-impedance traces (typically 50 ohm single-ended) on the registered outputs to preserve the 25-ohm damping benefit. Keep trace stubs under 5 mm; vias should be placed on the inner edge of the Daisy chain to avoid reflections. Place a ground plane on an adjacent layer for return-current continuity, especially under the simultaneous-switching output banks.
The BusHold feature only retains a valid logic state when the input/output voltage is within the datasheet's guaranteed VIH/VIL window. If a downstream driver could leave the QS74FCT4X32H374AQ3's output in an undefined mid-rail state (e.g., during in-circuit test), add a weak external pull-up to force a known state. Do not exceed 7V on VCC - the part is not 3.3V tolerant on its outputs. Last-time-buy orders should be coordinated with Rochester Electronics or a contract manufacturer because the NRND status means stock is finite.
Compliance-Informationen
MilliPak-80 package is a legacy QSI/Renesas package style. Lead-free / RoHS status not confirmed in the provided web snippets for this specific MPN - verify against the original QSI datasheet or contact Rochester Electronics for a Certificate of Compliance before new deployments.
