74CB3Q3257BQX - 4-Bit SPDT FET Bus Switch, 5V | Nexperia
MPN： 74CB3Q3257BQX ✓ 啟用中74CB3Q3257BQX 概覽
A FET bus switch (also called a bus multiplexer/demultiplexer) is a passive analog switch implemented with parallel NMOS transistors whose gates are driven by an internal charge pump. Unlike mechanical or relay switches, FET switches have no moving parts, offer nanosecond switching speeds, draw zero quiescent current through the signal path, and present a near-ideal connection when ON. They sit in the hierarchy: signal switch -> analog switch -> multiplexer/demultiplexer -> logic IC -> semiconductor.
Key features include 4 ohm typical on-resistance, 200 MHz bandwidth, undershoot-protection diodes on I/Os, partial-power-down support via Ioff circuitry, and standard CMOS inputs with TTL-compatible switching thresholds. A single select input (S) routes each of the four channels, while an active-high output enable (OE) places all channels in high-impedance when asserted. The DHVQFN-16 package provides an exposed thermal pad and is qualified to -40 C to +85 C operation.
Typical applications include USB 2.0/3.0 port switching, I2C/SPI/UART signal multiplexing, HDMI/DVI link switching, server hot-plug routing, and general-purpose high-speed signal gating. The wide 2.3 V to 3.6 V supply range and 5 V tolerant I/Os make the 74CB3Q3257BQX well suited for mixed-voltage board designs where signals exceed the local supply rail.
When designing with this part, place decoupling capacitors as close as possible to VCC and treat the exposed pad as a thermal/ground stitch to the inner PCB ground plane. Note that signal paths are unidirectional in terms of bandwidth optimization; for true bidirectional analog signals use a true analog switch variant. Always confirm output-enable logic polarity before board bring-up.
This page synthesizes distributor pricing, package-specific drop-in alternatives, and practical design notes that are not consolidated in the manufacturer datasheet, providing a single reference for component selection, replacement, and PCB redesign decisions.
直接替換替代品，適用於 74CB3Q3257BQX — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： 74CB3Q3257BQX （相同外形與佔位） — 差異在於 Function, Operating Temperature, Package.
74CB3Q3257BQ
✅ 直接替換📋 參考替代品（不在目錄中）
74CBTLV3257BQ
✅ 直接替換📋 參考替代品（不在目錄中）
SN74CB3Q3257
✅ 直接替換📋 參考替代品（不在目錄中）
SN74CBTLV3257PWR
✅ 直接替換聯絡詢價
查看資料表 →74CB3Q3257DSG
✅ 直接替換📋 參考替代品（不在目錄中）
74CB3Q3257BQX 最大額定值與電氣特性
| 功能 | FET bus switch / multiplexer-demultiplexer |
| Configuration | 4 x 2:1 (SPDT), 4 channels |
| On-Resistance (Ron) | 4 ohm typical |
| Ron Flatness | Improved (charge-pump biased) |
| Supply Voltage (VCC) | 2.3 V to 3.6 V |
| Signal Pass Voltage | Up to 5 V (when VCC = 3.3 V) |
| Input Type | CMOS control, TTL-compatible threshold |
| Select Input (S) | 1 (shared across 4 channels) |
| Output Enable (OE) | 1, active-HIGH disables all channels |
| Ioff / Partial Power Down | Supported |
| 工作溫度 | -40 C to +85 C |
| 封裝 | 16-DHVQFN (2.5 x 3.5 mm), SOT763 |
| RoHS 狀態 | Compliant |
| Lead-Free | Yes |
| 濕度敏感等級 (MSL) | 1 (per JEDEC J-STD-020) |
74CB3Q3257BQX 腳位配置
| 腳位 1 | 1B1 — Channel 1, port B, signal 1 |
| 腳位 2 | 1A — Channel 1, common port A |
| 腳位 3 | 1B2 — Channel 1, port B, signal 2 |
| 腳位 4 | 2B1 — Channel 2, port B, signal 1 |
| 腳位 5 | 2A — Channel 2, common port A |
| 腳位 6 | 2B2 — Channel 2, port B, signal 2 |
| 腳位 7 | GND — Ground reference |
| 腳位 8 | OE — Output enable, active-HIGH disables all channels |
| 腳位 9 | S — Select input (shared across all channels) |
| 腳位 10 | 3B1 — Channel 3, port B, signal 1 |
| 腳位 11 | 3A — Channel 3, common port A |
| 腳位 12 | 3B2 — Channel 3, port B, signal 2 |
| 腳位 13 | 4B1 — Channel 4, port B, signal 1 |
| 腳位 14 | 4A — Channel 4, common port A |
| 腳位 15 | 4B2 — Channel 4, port B, signal 2 |
| 腳位 16 | VCC — Supply voltage, 2.3 V to 3.6 V |
典型應用
74CB3Q3257BQX 適用於 7 應用s: USB 2.0 Port Multiplexing, I2C/SPI Bus Muxing, HDMI/DVI Signal Routing, Server Hot-Plug Card Routing, Audio Codec Source Switching, Industrial GPIO Expansion, Battery-Powered Sensor Multiplexing.
USB 2.0 Port Multiplexing
The 74CB3Q3257BQX routes USB 2.0 differential pairs between two sources (Type-A and Type-C) sharing a single host controller. Its 4 ohm on-resistance and flat unipolar Ron from an internal charge pump preserve signal integrity at USB 2.0 high-speed (480 Mbps). Placed between the connector ESD array and the host PHY, it adds nanosecond-scale switching with negligible insertion loss. Unlike mechanical or relay switches, the FET bus switch draws zero DC bias current through the data path, keeping idle power at zero. The 2.3 V to 3.6 V VCC range aligns directly with USB 2.0 PHY supply rails.
推薦
I2C/SPI Bus Muxing
The 74CB3Q3257BQX serves as a 4-channel 2:1 mux for I2C, SPI, or UART buses connecting a master MCU to one of two slaves per channel. The 5 V signal pass capability from a 3.3 V supply lets it bridge 3.3 V MCUs to 5 V peripherals without level shifters. With undervoltage-protected I/Os and Ioff partial-power-down, removing VCC does not back-drive the upstream master. The 16-pin DHVQFN footprint allows a compact bus-routing island adjacent to the MCU.
推薦
HDMI/DVI Signal Routing
The 74CB3Q3257BQX can switch HDMI/DVI TMDS pairs between two sources sharing one display, especially in docking stations and KVM equipment. The 4 ohm Ron minimizes eye-diagram degradation at TMDS clock rates up to ~165 MHz, though signal-integrity margins should be validated in-system. The active-high OE pin lets an HDMI controller gate the source path during cable hot-plug events. Designers should pay attention to PCB layout for 100 ohm differential pairs to preserve impedance continuity.
推薦
Server Hot-Plug Card Routing
In server backplanes, the 74CB3Q3257BQX multiplexes low-speed management signals (I2C, GPIO, present-sense) between hot-swappable cards. The Ioff feature prevents back-powering when a card is removed, protecting upstream controllers. Its DHVQFN-16 footprint saves board area in dense 1U server designs, and the -40 C to +85 C operating range covers data-center ambient. The active-high OE enables a fault-tolerant default state during inrush.
推薦
Audio Codec Source Switching
The 74CB3Q3257BQX routes I2S or analog-mute lines between two audio codecs in a multi-source headphone amplifier or mixer. Because the FET bus switch has near-zero Ron flatness through the audio spectrum (20 Hz to 20 kHz), it does not introduce channel imbalance. The 5 V tolerant I/Os permit switching line-level signals above the local 3.3 V supply. Designers should pair it with a dedicated audio MUX if THD+N is critical at the analog node.
推薦
Industrial GPIO Expansion
In industrial PLC and HMI modules, the 74CB3Q3257BQX doubles the number of usable GPIO pins by switching between two banks of peripherals. The industrial-grade -40 C to +85 C rating and wide VCC range make it suitable for factory-floor equipment. The internal charge pump keeps Ron stable across the industrial temperature range. The DHVQFN-16 footprint suits compact PLC daughter cards where PCB real estate is at a premium.
推薦
Battery-Powered Sensor Multiplexing
The 74CB3Q3257BQX multiplexes multiple low-power sensors to a single ADC input in battery-powered IoT designs. The near-zero quiescent current through the signal path extends battery life compared with active buffer muxes. The Ioff feature prevents back-powering through the switch when VCC collapses, preserving state and protecting the host. The 16-pin DHVQFN is well suited to coin-cell powered sensor nodes where PCB area is constrained.
推薦
推薦產品摘要
工程參考資料，適用於 74CB3Q3257BQX — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | 74CB3Q3257BQ | 74CBTLV3257BQ | SN74CB3Q3257 | SN74CBTLV3257 | 74CB3Q3257DSG |
|---|---|---|---|---|---|---|
| Brand | Nexperia | Nexperia | Nexperia | Texas Instruments | Texas Instruments | Diodes Incorporated |
| Package | DHVQFN-16 (SOT763, 2.5x3.5 mm) | DHVQFN-16 (SOT763) - same | DHVQFN-16 (SOT763) - same | DHVQFN-16 (BQQ) - same | DHVQFN-16 (BQB) - same | DHVQFN-16 - same |
| Function | 4 x 2:1 FET bus switch | 4 x 2:1 FET bus switch | 4 x 2:1 FET bus switch (low-voltage) | 4 x 2:1 FET bus switch | 4 x 2:1 FET bus switch (low-voltage) | 4 x 2:1 FET bus switch |
| Supply Voltage (VCC) | 2.3 V to 3.6 V | 2.3 V to 3.6 V | 2.3 V to 3.6 V | 2.3 V to 3.6 V | 2.3 V to 3.6 V | 2.3 V to 3.6 V |
| On-Resistance (Ron) | 4 ohm typical | 4 ohm typical | 5 ohm typical | 5 ohm typical | 5 ohm typical | 5 ohm typical |
| Output Enable (OE) Polarity | Active-HIGH disables | Active-HIGH disables | Active-HIGH disables | Active-HIGH disables | Active-HIGH disables | Active-HIGH disables |
| Operating Temp Range | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
| Ioff / Partial Power Down | Yes | Yes | Yes | Yes | Yes | Yes |
主要差異化特點
- Charge-pump biased gate for improved Ron flatness (對比74CBTLV3257BQ)
- Nexperia-second-source compatibility with TI SN74CB3Q3257 (對比SN74CB3Q3257)
- 5 V signal pass from 3.3 V supply without level shifters (對比Discrete NMOS pass gate)
設計說明
Place a 0.1 uF X7R decoupling capacitor within 3 mm of the VCC pin and stitch the exposed pad to the inner ground plane with at least four thermal vias. Keep switch trace impedance controlled (50 ohm single-ended, 90 ohm differential for USB/HDMI) and avoid routing switch paths near noisy power inductors. The exposed pad serves both thermal dissipation and ground return.
Estimated: at 480 Mbps USB 2.0 high-speed signaling, a 4 ohm Ron plus the package's ~1.5 nH lead inductance introduces approximately 0.6 dB of insertion loss and modest jitter. Maintain differential pair length matching within 150 mil, and place the switch as close to the connector ESD array as practical. For HDMI TMDS above 1 Gbps, prefer a true redriver and validate eye diagrams in-system.
The OE pin is active-HIGH (disables channels when asserted HIGH), which is opposite of the legacy 74HC245 direction convention - verify polarity at board bring-up. Never apply 5 V to VCC; the absolute-maximum VCC is 4.6 V. Signals on B1/A/B2 may exceed VCC up to 5 V when VCC is 3.3 V, but exceeding this range can latch the charge pump or damage ESD cells. Use the Ioff feature to safely remove VCC without back-powering upstream devices.
The 74CB3Q3257BQX draws a typical ICC of less than 1 mA in active operation plus charge-pump switching losses that scale with toggle frequency. Estimated: at 10 MHz toggle rate the ICC rises to approximately 3 mA. The internal charge pump draws brief current spikes during state changes - decouple VCC locally to prevent rail droop. No external pump capacitors are required.
合規資訊
RoHS compliant per Nexperia product page. Not AEC-Q100 qualified - choose 74CB3Q3257 automotive variant for vehicle applications. Halogen-free status not explicitly stated in the verified web data.
