STMicroelectronics 74VHC238TTR

Overview

74VHC238TTR from STMicroelectronics is a high-speed CMOS 3-to-8 line decoder with symmetrical output drive (±8 mA), 5.5 ns typical propagation delay at 5V, 2V–5.5V operating voltage range, and full input power-down protection enabling 0–7V tolerant inputs independent of VCC. It serves as an address decoder in memory systems and logic selection blocks in industrial control and embedded microcontroller peripherals.

For engineers reviewing the 74VHC238TTR datasheet, 74VHC238TTR pinout, 74VHC238TTR application, or 74VHC238TTR equivalent, key selection criteria include enable-input cascade capability (G1, G2A, G2B), latch-up immunity, ESD robustness (2 kV HBM), and 3.3V/5V mixed-voltage interface compatibility.

Technical Context

The 74VHC238 implements active-high decoding logic with three binary address inputs (A, B, C) and three independent enable inputs (G1 low-active, G2A/G2B high-active) that collectively gate all eight outputs (Y0–Y7). Its truth table defines mutually exclusive single-output activation when enabled, supporting hierarchical address decoding in multi-chip memory maps.

Designed using sub-micron C2MOS technology, it features balanced tPLH/tPHL delays, input hysteresis (28% VCC noise immunity), and rail-to-rail input tolerance - allowing safe interfacing between 5V controllers and 3V subsystems without level shifters.

Key Specifications

Pinout & Package

TSSOP-16 package (4.9 × 6.4 mm body, 0.65 mm pitch), thin shrink small outline with exposed pad not present; RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with SN74LV138APWR and 74HC238PW,118, the 74VHC238TTR uniquely combines 5.5 ns speed, ±8 mA drive, and 0–7 V input tolerance - making it optimal for high-reliability, mixed-voltage address decoding where timing margin and interface safety are co-constrained.

Availability

74VHC238TTR is available at Aetrix Electronics and suitable for memory subsystem design, industrial I/O expansion, mixed-voltage interface bridging, and embedded bootloader selection requiring stable component supply and long-term lifecycle support.

Supply support for 74VHC238TTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The 74VHC series targets high-speed, low-power logic applications demanding robustness across wide voltage and temperature ranges - particularly in industrial control, instrumentation, and legacy-system upgrades.

FAQ

Can the 74VHC238TTR operate safely with VCC = 3.3 V while accepting 5 V inputs?

Yes. Its input structure tolerates 0–7 V regardless of VCC, including 5 V signals applied during 3.3 V operation. This eliminates external level-shifting components and prevents damage or false triggering due to voltage mismatch - verified per Absolute Maximum Ratings (VI = −0.5 to +7.0 V) and Input Equivalent Circuit (Figure 2).

What is the maximum capacitive load the 74VHC238TTR can drive while maintaining specified propagation delay?

The AC Electrical Characteristics table specifies tPLH/tPHL values for CL = 15 pF and CL = 50 pF loads. At 5.0 V VCC, delay remains within 9.5 ns (max) up to 50 pF. Driving heavier loads increases delay nonlinearly and may degrade edge integrity - use 50 pF as the practical upper limit for timing-critical applications.

How does the enable-input logic (G1, G2A, G2B) support cascading multiple decoders?

G1 is active-low; G2A and G2B are active-high. To cascade, tie the selected Yx output of a higher-order decoder to G1 of a subordinate decoder, while holding G2A/G2B low. This creates hierarchical decoding: e.g., first-stage selects bank, second-stage selects device within bank - confirmed by Truth Table and Logic Diagram (Figure 3).

Is the 74VHC238TTR suitable for automotive applications per AEC-Q100?

No. While rated for −55°C to +125°C operation and featuring enhanced latch-up immunity, STMicroelectronics does not qualify the 74VHC238TTR under AEC-Q100. For automotive use, consider the pin-compatible 74VHC238QTR (qualified to Grade 2) or SN74LV138A-Q1, which undergo full stress testing per AEC-Q100 Rev H.