My Inquiry
My Account
Renesas QS3251QG
- Part No.:
- QS3251QG
- Manufacturer:
- Renesas
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
QS3251QG.pdf
- Description:
- IC MUX/DEMUX 1 X 8:1 16QSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,253
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
QS3251QG from Renesas Electronics is a high-speed CMOS 8:1 bidirectional multiplexer/demultiplexer with TTL-compatible control inputs, 5Ω typical ON resistance, zero propagation delay, and industrial temperature range (–40°C to +85°C). It serves as a logic-level signal routing device in video/audio switching, hot-swap interfaces, and voltage translation between 5V and 3.3V domains.
For engineers reviewing the QS3251QG datasheet, QS3251QG pinout, QS3251QG application, or QS3251QG equivalent, key selection criteria include guaranteed 5Ω switch RON, undershoot clamp diodes on all I/Os, 3-state output enable control, and compatibility with legacy 74F251/74FCT251 logic families.
Technical Context
The QS3251QG implements an enhanced N-channel FET bus switch architecture with no inherent body diode to VCC, enabling true bidirectional signal flow without DC path constraints. Its control logic accepts standard TTL voltage levels (VIL ≤ 0.8 V, VIH ≥ 2.0 V) and drives three select lines (S0–S2) plus active-low enable (E) to route one of eight inputs (I0–I7) to the Y output.
Switching performance is defined by sub-nanosecond turn-on/turn-off delays (tPZL/tPLZ ≤ 6.6 ns max), negligible propagation delay contribution (<0.25 ns typical), and low dynamic power consumption (0.25 mA/MHz). All I/O pins feature integrated undershoot clamp diodes for robust ESD protection during hot-plug events.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch ON Resistance | 5 Ω typical at VCC = 5 V, 0 V input - enables low-loss analog/digital signal routing with minimal voltage drop |
| Propagation Delay | <0.25 ns typical - adds negligible timing overhead in high-speed data paths |
| Operating Temperature | –40°C to +85°C - supports industrial-grade reliability without derating |
| Supply Voltage Range | –0.5 V to +7 V - accommodates 3.3 V, 5 V, and mixed-voltage system interfacing |
| Input Clamp Diodes | Integrated on all switch and control inputs - protects against –3 V AC undershoot transients |
| Output Drive Capability | ±120 mA DC - supports direct connection to moderate capacitive loads without external buffering |
| Power Dissipation | 0.5 W max at TA = 85°C - allows operation in compact PCB layouts without forced cooling |
Pinout & Package
QS3251QG is packaged in a 16-pin QSOP (Quarter Size Outline Package) with green RoHS-compliant finish. Pin spacing is 0.65 mm, body width 3.9 mm, and total footprint compatible with SOIC-16 footprints using appropriate pad layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| I0–I7 | Data Inputs/Outputs | Bidirectional signal terminals; connected to Y when selected, high-impedance otherwise |
| S0–S2 | Select Inputs | TTL-compatible binary address lines determining which Ix connects to Y (0–7) |
| E | Enable Input | Active-low control: Y = Hi-Z when E = HIGH; functional routing enabled when E = LOW |
| Y | Data Output/Input | Single bidirectional terminal routed to selected Ix; 3-state when E = HIGH |
| VCC | Positive Supply | Primary power rail (5 V nominal); supplies internal logic and switch bias |
| GND | Ground Reference | Signal and power return path; required for clamp diode operation and logic reference |
| NC | No Connect | Pin 9 is internally unconnected; must be left floating or tied to GND per layout best practice |
Key Features
| Feature | Design Value |
|---|---|
| Zero-propagation-delay switching | RC-limited delay <0.25 ns ensures timing-critical paths remain unaffected by mux insertion |
| Undershoot clamp diodes on all I/Os | Withstands –3 V transient pulses, enabling safe hot-swapping in live backplanes |
| 5 Ω low ON-resistance FET switches | Minimizes signal attenuation and distortion for analog video, audio, and digital buses |
| Pin-compatible with 74F251/74FCT251 | Direct drop-in replacement for legacy logic muxes without PCB redesign |
| TTL-compatible control inputs | Operates with standard 5 V logic drivers; no level-shifting circuitry required |
Applications
| Video Signal Routing | Hot-Swappable Peripheral Interface |
|---|---|
Use Scenario: Switching multiple HDMI or analog RGB video sources to a single display controller in broadcast equipment. IC Role / Device Role / Timing Role: Bidirectional 8:1 analog mux providing low-distortion, low-delay signal path selection. Use Value: 5 Ω RON and <0.25 ns delay preserve signal integrity across DC–100 MHz bandwidths without gain compensation. | Use Scenario: Enabling safe insertion/removal of USB or PCIe daughter cards in server blade chassis. IC Role / Device Role / Timing Role: Signal isolation gate with undershoot clamping and 3-state control during plug events. Use Value: Integrated –3 V clamp diodes prevent latch-up during hot-dock transients; E pin enables deterministic isolation sequencing. |
| 5V-to-3.3V Voltage Translation | Legacy Logic System Upgrade |
Use Scenario: Interfacing 5 V microcontroller GPIOs to 3.3 V FPGA configuration pins in mixed-voltage embedded systems. IC Role / Device Role / Timing Role: Passive bidirectional level translator leveraging FET conduction without direction control. Use Value: No external bias or direction pin needed; operates across full 0–5 V input range while driving 3.3 V logic thresholds reliably. | Use Scenario: Replacing obsolete 74F251 multiplexers in industrial PLC I/O modules with improved speed and noise immunity. IC Role / Device Role / Timing Role: Pin- and function-identical upgrade delivering zero ground bounce and lower power. Use Value: Drop-in replacement eliminates redesign cost; 3 μA quiescent current reduces standby power by >90% vs. original TTL part. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8:1 analog/digital multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74CBT3251PWR | Higher RON (7 Ω typ), same pinout, identical control interface, slightly higher ICCD (0.35 mA/MHz) | Valid for 3.3 V–5 V translation but less optimal for high-fidelity analog video due to higher on-resistance | Preferred where TI supply chain preference applies and minor RON increase is acceptable |
| 74FCT251CTSO | Legacy TTL part; 12 ns propagation delay, no undershoot clamps, 25 mA IOUT drive limit | Only suitable for non-critical digital-only muxing; cannot replace QS3251QG in hot-swap or analog applications | Use only for legacy repair; not recommended for new designs requiring robustness or speed |
Compared with SN74CBT3251PWR and 74FCT251CTSO, the QS3251QG delivers superior analog fidelity via 5 Ω RON, essential hot-swap safety via integrated clamps, and zero-delay routing-making it the only choice for mixed-signal, high-reliability, or timing-sensitive implementations.
Availability
QS3251QG is available at Aetrix Electronics and suitable for video switching, hot-swap peripheral interfaces, voltage translation, and legacy logic upgrades requiring stable component supply across industrial temperature ranges.
Supply support for QS3251QG 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
Renesas Electronics Corporation is a global semiconductor leader delivering microcontrollers, analog power, and connectivity solutions for automotive, industrial, and IoT applications.
The QS3251QG belongs to Renesas' QuickSwitch® bus switch product line, engineered specifically for low-latency, bidirectional signal routing in mixed-voltage, hot-plug-capable systems.
FAQ
What is the maximum operating voltage for QS3251QG?
The QS3251QG supports a supply voltage range of –0.5 V to +7 V on all terminals except VCC, and –0.5 V to +7 V on VCC. This allows safe operation with 3.3 V, 5 V, and mixed-voltage interfaces. The absolute maximum rating ensures robustness against transient overvoltage events without latch-up, provided thermal limits are observed.
Does QS3251QG support bidirectional signal flow?
Yes, the QS3251QG is a fully bidirectional bus switch: any of the I0–I7 pins can serve as input or output depending on signal direction, with Y acting as the common port. This enables flexible routing in both multiplexer and demultiplexer configurations without external direction control logic.
Is QS3251QG pin-compatible with standard logic multiplexers?
Yes, the QS3251QG is explicitly pin- and function-compatible with the 74F251, 74FCT251, and 74ALS/AS/LS251 8:1 multiplexers. Pin mapping, control logic behavior, and package outline match exactly-enabling drop-in replacement without PCB modification.
What is the purpose of the NC pin on QS3251QG?
Pin 9 of the QS3251QG is marked NC (No Connect) and is internally unconnected. It must be left floating or tied to GND per PCB layout best practices to avoid parasitic coupling. It does not affect functionality and has no electrical role in normal operation.
How does QS3251QG handle undershoot transients during hot-swap events?
The QS3251QG integrates undershoot clamp diodes on all switch and control inputs, rated to withstand –3 V AC transients (pulse width ≤20 ns). This prevents negative voltage excursions from damaging downstream logic or causing metastability, making it suitable for hot-docking applications like modular server backplanes.
QS3251QG Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Renesas
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Multiplexer/Demultiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- -
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QSOP
QS3251QG FAQ
1.How can I place an order for QS3251QG through Aetrix?
Please submit a Request for Quotation (RFQ) for QS3251QG on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for QS3251QG reliable?
The price and inventory of QS3251QG are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for QS3251QG is usually 5 days.
3.What payment methods are accepted for QS3251QG?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for QS3251QG transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for QS3251QG?
QS3251QG orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your QS3251QG order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for QS3251QG?
For technical support, including QS3251QG datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your QS3251QG requirements.
6.How does Aetrix verify that QS3251QG is sourced from the original manufacturer or authorized distributors?
All QS3251QG products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that QS3251QG meets industry standards.
7.What is the process for return or replacement of QS3251QG?
All QS3251QG units undergo pre-shipment inspection (PSI). If there is an issue with QS3251QG, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The QS3251QG part is unused and in its original packaging.
Return procedure for QS3251QG:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
QS3251QG Tags
-
SN74HC138DR
Texas Instruments
-
TC7SB3157CFU,LF(CT
Toshiba Semiconductor and Storage
-
74CBTLV3257PW,118
Nexperia USA Inc.
-
SN74CBTLV3257PWR
Texas Instruments
-
74CBTLV3257GUX
Nexperia USA Inc.
-
74HC154BQ,118
Nexperia USA Inc.
-
P3S0200GMX
NXP USA Inc.
-
SN74CB3Q3245PWR
Texas Instruments
-
SN74CB3Q3257RGYR
Texas Instruments
-
TCA9543APWR
Texas Instruments
-
TCA9546APWR
Texas Instruments
-
SN74HC138N
Texas Instruments
Tech Hub
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
