SN74LVC1G241DBVR Design Guide for Tri-State Bus Buffer Applications

Bottom Line: When designing isolation between two logic domains on a shared bus, the SN74LVC1G241DBVR — a single non-inverting buffer with 3-state outputs in a 5-pin SOT-23 package — handles 32 mA outputs, 1.65 V to 5.5 V supply, and 1.0 ns max propagation delay at 3.3 V. Three rules dominate: (1) tie OE high or low through a defined pull resistor, never float it, (2) match VCC to the driven domain (overdrive tolerant up to 5.5 V on inputs even at 1.8 V VCC), and (3) place a 0.1 µF X7R bypass within 5 mm of the package pins to keep the partial-power-down (Ioff) protection effective.

What the SN74LVC1G241DBVR Actually Does

The SN74LVC1G241DBVR is a single-channel non-inverting bus buffer / driver with a 3-state output, manufactured in TI's LVC family on a low-voltage CMOS process. It is functionally one quarter of the classic SN74LVC241 octal buffer, repackaged in a tiny 5-pin SOT-23 (DBV) for point-of-load isolation rather than wide-bus driving. The output enable (OE) pin gates the output: when OE is asserted, the input data flows to the output; when OE is deasserted, the output goes to a high-impedance state and the device looks electrically disconnected.

That high-Z behavior is exactly what makes the part useful in wired-OR situations where multiple sources share one trace: a microcontroller GPIO, a sensor, and a debug header can all drive the same line if only one buffer is enabled at a time. Compared with SN74LVC1G125DBVT, which has the same function in the LVC1G125 line, the SN74LVC1G241DBVR uses an active-high OE; choose by the polarity that matches your enable-signal source so you do not need an extra inverter.

Design Considerations

Supply-Voltage Selection and Mixed-Voltage Operation

The supply voltage you pick determines the entire timing budget — pick it from the driven side, not the driving side. The SN74LVC1G241DBVR supports 1.65 V to 5.5 V VCC with overvoltage-tolerant inputs up to 5.5 V regardless of VCC; this means a 1.8 V supply rail can reliably accept 3.3 V CMOS levels at the input without level shifting. Set VCC equal to the destination logic family's voltage so output VOH meets the receiver's VIH spec with margin.

Avoid the common mistake of running VCC at the source voltage. If a 3.3 V MCU drives a 1.8 V FPGA through a 3.3 V-supplied buffer, the buffer will output 3.3 V and overstress the FPGA input. Set VCC = 1.8 V instead, let the input tolerate 3.3 V (because the part is overvoltage-tolerant on inputs), and let the output meet 1.8 V CMOS levels. This single-buffer level-translation trick eliminates a separate translator IC such as a TXS0102 in many designs.

Drive Strength, Capacitive Load, and Edge Rate

Output drive strength dictates how fast the device can charge a transmission line and how clean the resulting edges will be. The SN74LVC1G241DBVR specifies IOL / IOH = ±32 mA at VCC = 3.3 V, with propagation delay ≤ 1.0 ns and a typical CL = 15 pF reference. Real PCB capacitance on a few-centimeter trace adds 5–8 pF; under heavy capacitive load the rise time can lengthen and SI degrades. Use the formula t_r ≈ 2.2 × R_eff × C_load with R_eff ≈ VCC / IOL to estimate edge rates; if t_r approaches 30% of bit period, lower CL by shortening the route or using a series source-termination resistor of 22–33 Ω placed within 5 mm of the buffer output.

Edge rates that are too fast can also cause problems. A 0.5 ns edge into 8 cm of unterminated trace radiates at the third harmonic into the FM band and creates ground-bounce on the buffer side. Add 22–33 Ω series-source termination on outputs feeding > 3 cm traces; the termination minimally affects propagation delay (< 200 ps) but drops reflections to the noise floor.

Output Enable Behavior and Glitch Prevention

The OE pin must be defined at all times, including during power-up sequencing. The SN74LVC1G241DBVR does not have an internal pull-up or pull-down on OE — float the pin and you get an undefined output that may oscillate during transients. Drive OE actively from a known signal, or use a 10 kΩ pull-up to VCC (output enabled by default, disabled when MCU drives low) or pull-down to GND (output disabled by default), depending on the safe state. The 10 kΩ value balances leakage against switching speed; values above 100 kΩ make OE susceptible to coupled noise on the trace.

For glitch-free output engagement, use a synchronizer on the OE control if it crosses a clock domain. A two-flip-flop synchronizer ahead of OE prevents the metastability that would otherwise let the output briefly enable mid-transition, corrupting a shared bus.

Power Sequencing and Partial-Power-Down (Ioff)

The Ioff feature lets the SN74LVC1G241DBVR sit on a powered bus while its own VCC is removed. With Ioff active, the input and output pins present a high impedance even with VCC = 0 V, so the buffer does not load the bus or back-feed current into its own supply. This is critical when the buffer isolates an FPGA that is power-gated for low-power modes. Confirm Ioff guarantees by reading the datasheet's "VCC = GND" leakage row — typically < 10 µA — and check that any pull-up resistors on the bus respect that leakage so the bus high level is preserved.

Recommended Solutions

Option A: 1-of-N Bus Sharing in Test or Debug

When a debug header, an MCU GPIO, and an in-circuit programmer must share one signal line, place an SN74LVC1G241DBVR on each source's connection. Drive OE active-high from a one-hot decoder so exactly one buffer is enabled at any time. The 32 mA drive easily handles a 50–100 pF debug header capacitance, and the 3-state output guarantees zero load when the buffer is disabled. Use SN74LVC2G241DCTR for the dual-channel equivalent if two related signals share enable logic.

Option B: Level Translation with Single VCC

Connect the source side directly to inputs (overvoltage tolerant up to 5.5 V), set VCC to the destination voltage, and route the output to the destination receiver. Eliminates a dedicated level translator and saves PCB area. A typical use case is a 3.3 V STM32 MCU driving a 1.8 V camera sensor: VCC = 1.8 V, input gets 3.3 V CMOS, output presents clean 1.8 V signaling. For inverting requirements, swap to SN74LVC1G240DBVR which performs the same translation with logic inversion.

Option C: Hot-Swap or Backplane Insertion

When a daughtercard inserts into a powered backplane, the SN74LVC1G241DBVR's Ioff feature ensures the disconnected card does not corrupt the backplane bus. Power the buffer from the daughtercard's local supply; while the card is unpowered the buffer presents high-Z. Once the card powers up, hold OE low until the local clock and reset are stable, then enable OE through a synchronized control signal. This pattern eliminates the need for dedicated hot-swap controllers in low-current digital backplanes.

Option	Best for	Drive strength	Key constraint
A — 1-of-N sharing	Debug, programming, multi-master probes	32 mA	One-hot OE control needed
B — Level translation	MCU↔FPGA / sensor across rails	32 mA at destination V	VCC must equal driven domain
C — Hot-swap	Backplane insertion	32 mA	Sequencing OE during power-up

Common Pitfalls and Troubleshooting

Pitfall 1: Floating OE pin. A floating OE causes the buffer output to oscillate or drift to an undefined level. Symptom: intermittent bus errors that disappear when a fingertip touches the OE trace. Fix: add a 10 kΩ pull resistor to the safe-state rail.

Pitfall 2: Mismatched VCC and destination logic. Running VCC = 3.3 V into a 1.8 V FPGA input destroys the receiver over time. Symptom: receiver chip fails after weeks in the field. Fix: set VCC to the receiving domain voltage and rely on the 5.5 V-tolerant inputs.

Pitfall 3: Insufficient bypass capacitance. A missing or distant bypass cap adds inductance to the supply path and compromises both Ioff guarantees and edge rates. Symptom: ground bounce, jitter, or coupled noise. Fix: place a 0.1 µF X7R within 5 mm of the VCC pin, with a short fat trace or shared via to the ground plane.

Pitfall 4: Forgotten series termination. Long traces (> 3 cm) without source termination produce visible reflections that violate setup/hold at the receiver. Symptom: occasional sampling errors that worsen with temperature. Fix: insert a 22–33 Ω resistor immediately after the buffer output.

Pitfall 5: Wrong drive direction in pin-compatible swap. SN74LVC1G241 (active-high OE) and SN74LVC1G240 (inverting variant) share footprints but invert the data signal. Symptom: receiver sees the wrong logic level after a "drop-in" change. Fix: confirm logic polarity from the datasheet truth table before substituting.

FAQ

What is the maximum supply voltage I can apply to the SN74LVC1G241DBVR?

The SN74LVC1G241DBVR supports VCC from 1.65 V to 5.5 V; the absolute-maximum specified by TI's datasheet is 6.5 V, but operate well within the 1.65–5.5 V recommended range. Inputs are 5.5 V-tolerant independent of VCC, allowing the device to receive higher-voltage signals while running at a lower local supply for level translation.

Can I leave the OE pin floating if I always want the buffer enabled?

No. CMOS inputs without a defined level can drift, oscillate, and cause undefined output behavior or excess current. Tie OE to GND through a 10 kΩ pull-down resistor for "always enabled" if your data sheet specifies active-low OE, or directly drive OE from a microcontroller pin. The SN74LVC1G241DBVR uses an active-low OE on this part, so a pull-down enables the buffer permanently while still allowing emergency disable from a wired-OR signal.

How much delay does the SN74LVC1G241DBVR add to a signal path?

At VCC = 3.3 V and CL = 15 pF, propagation delay is typically 2.2 ns and 4.0 ns max. At VCC = 1.8 V it lengthens to roughly 4.0 ns typical and 6.5 ns max. For setup/hold-critical paths, budget the worst-case spec from the datasheet at your operating voltage and add board-level capacitance derating per the IBIS model.

Does the SN74LVC1G241DBVR work safely if VCC is removed while inputs are still driven?

Yes — that is exactly what the Ioff feature enables. With VCC = 0 V, the input and output pins go high-impedance and present minimal leakage (typically < 10 µA), so the device will not back-feed current into the supply or pull the bus low. This makes it suitable for hot-swap and partial-power-down systems, provided the input drive level stays within the 5.5 V tolerance window.

How do I choose between SN74LVC1G241 and SN74LVC1G125?

Both are single-channel buffers with 3-state outputs, but the SN74LVC1G241DBVR has active-low OE while the SN74LVC1G125 has active-high OE. Pick the one whose enable polarity matches your control signal so you avoid an extra inverter. Drive strength, supply range, and propagation delay are essentially equivalent within the same DBV package. For comparison logic-family alternatives, see our NOR gate selection guide.

Bottom Line and Next Steps

The SN74LVC1G241DBVR earns its place in modern designs because it solves three problems with one tiny part: bus sharing, level translation, and partial-power-down isolation. Match VCC to the driven domain, anchor OE through a defined resistor, and place a tight bypass capacitor — those three rules cover 90% of the pitfalls.

For volume sourcing of TI logic in single-channel SOT-23 packages, search FindMyChip for current authorized-distributor pricing across 200+ verified suppliers, or request a quote directly. Need a different drive polarity or channel count? Compare the SN74LVC1G family on the same product page and our team can quote in 24 hours.