Renesas QS3126S1G

Overview

QS3126S1G from Renesas Electronics is a high-speed CMOS quadruple bus switch with individual active-high enables, designed for bidirectional signal routing between A and Y buses. It features 5 Ω typical ON resistance at 5 V, zero propagation delay, undershoot clamp diodes on all inputs, and operates across –40°C to +85°C. It is used in voltage translation (5 V ↔ 3.3 V), hot-swapping, and clock gating applications.

For engineers reviewing the QS3126S1G datasheet, QS3126S1G pinout, QS3126S1G application, or QS3126S1G equivalent, key selection criteria include ON-resistance matching, enable timing (tPZL/tPLZ < 6.5 ns), industrial temperature support, SOIC-14 package compatibility, and absence of ground bounce in high-speed digital isolation.

Technical Context

The QS3126S1G implements four independent N-channel FET switches with no inherent body diode to V_CC, enabling true bidirectional signal flow without forward voltage drop or reverse conduction. Each channel has a dedicated active-high OE input controlling connection between corresponding A and Y terminals.

It operates with 5 V ±5% supply, supports DC switch voltages from –0.5 V to +7 V, and guarantees logic thresholds of V_IL ≤ 0.8 V and V_VH ≥ 2 V. The device adds no measurable propagation delay beyond RC time constant (~0.25 ns at 50 pF), making it suitable for timing-critical bus isolation.

Key Specifications

Pinout & Package

QS3126S1G is supplied in a 14-pin Small Outline IC (SOIC) package (package code DCG14), with 1.27 mm pitch, 8.65 mm × 3.91 mm body size, and standard JEDEC MS-012AC footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus switch applications.

Compared with SN74CBT3126DBR and 74LVC1G3157GW, the QS3126S1G offers guaranteed industrial temperature operation, lower off-state capacitance (7 pF), and integrated quad-channel layout-making it optimal for fixed 5 V, high-reliability bus isolation where PCB real estate and thermal stability are prioritized.

Availability

QS3126S1G is available at Aetrix Electronics and suitable for industrial control systems, embedded computing platforms, and storage subsystems requiring stable component supply amid end-of-life transitions.

Supply support for QS3126S1G 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, infrastructure, and IoT applications.

The QS3126S1G belongs to Renesas' QuickSwitch® family of high-speed bus switches, engineered specifically for zero-delay, low-noise signal routing in industrial and computing systems demanding deterministic timing and hot-swap reliability.

FAQ

What is the maximum supply voltage rating for QS3126S1G?

The QS3126S1G supports a maximum supply voltage (V_TERM) of +7 V relative to ground, with absolute maximum ratings specifying –0.5 V to +7 V on all terminals except V_CC. This allows safe operation under transient overvoltage conditions common in industrial environments. Exceeding these limits may cause permanent damage. The recommended operating V_CC remains 5 V ±5%, and the QS3126S1G must not be operated continuously above 7 V.

Does QS3126S1G support bidirectional signal flow between A and Y pins?

Yes, the QS3126S1G supports true bidirectional signal flow between each A and Y pair (e.g., 1A ↔ 1Y). Its enhanced N-channel FET structure eliminates the inherent body diode to V_CC, preventing unwanted conduction and enabling symmetrical signal transmission in either direction without external direction control. This behavior is confirmed in the functional block diagram and pin description section of the official datasheet for QS3126S1G.

Is QS3126S1G pin-compatible with standard TTL logic devices?

The QS3126S1G is explicitly stated as pin-compatible with the 74'126 function in its features list. While it is not a TTL device, its 14-pin SOIC layout matches the industry-standard 74-series footprint, allowing direct replacement in existing PCBs designed for 74LS126 or 74HC126-provided voltage and timing requirements are verified. The QS3126S1G retains identical pin numbering and terminal roles (e.g., OE, A, Y) as those legacy parts.

What is the significance of "zero ground bounce" in QS3126S1G?

"Zero ground bounce" means the QS3126S1G's switch architecture avoids injecting transient current spikes into the ground plane during switching transitions-a common issue in conventional logic buffers. This is achieved via low-impedance FET paths and optimized internal layout. For designs using QS3126S1G in high-speed bus isolation, this eliminates noise coupling into sensitive analog sections or clock domains, improving overall system signal integrity without requiring additional decoupling or layout mitigation.

Is QS3126S1G still recommended for new designs?

No-QS3126S1G is marked "NOT RECOMMENDED FOR NEW DESIGNS" and classified as OBSOLETE per the Renesas datasheet revision dated November 30, 2025. An End-of-Life notice (PLC230010) sets the last-time-buy date as July 31, 2024. While Aetrix Electronics maintains limited inventory for legacy support, engineers designing new systems should evaluate alternatives such as SN74CBT3126DBR or consult Renesas for qualified replacements before committing to QS3126S1G.