Texas Instruments SN74HC373NSR

Overview

SN74HC373NSR from Texas Instruments is an octal transparent D-type latch with 3-state outputs, operating across 2V–6V supply. It features eight independent latches sharing common LE and OE controls, 13ns typical propagation delay at 5V, ±6mA output drive, and high-current 3-state outputs capable of driving up to 15 LSTTL loads - used in bidirectional bus buffering and I/O port expansion in industrial microcontroller systems.

For engineers reviewing the SN74HC373NSR datasheet, SN74HC373NSR pinout, SN74HC373NSR application, or SN74HC373NSR equivalent, this page delivers verified functional behavior, real-world timing constraints (e.g., 13ns tpd, 13ns tdis), package-specific thermal metrics (RθJA = 113.4°C/W for NS), and precise latch/3-state control logic mapping - critical for bus isolation, data capture timing, and PCB layout validation.

Technical Context

The SN74HC373NSR implements eight edge-transparent D latches synchronized by a shared active-high latch-enable (LE) signal: when LE is high, Q outputs mirror D inputs; when LE goes low, outputs retain the last sampled D state. Its active-low output-enable (OE) independently places all eight outputs into high-impedance mode without affecting internal latch states.

This dual-control architecture enables precise separation of data sampling (via LE) and bus release (via OE), supporting time-critical applications such as address/data multiplexing, parallel I/O expansion, and synchronous bus arbitration where deterministic hold timing and clean bus disconnection are required.

Key Specifications

Pinout & Package

SN74HC373NSR is packaged in a 20-pin SOP (Small Outline Package) with 15.00 mm × 5.30 mm body size, surface-mount compatible, RoHS-compliant, and rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal transparent latch with 3-state output applications.

Compared with SN74HC373NSR, SN74HCT373NSR offers tighter TTL-compatible input thresholds for legacy 5V systems but consumes more quiescent current, while 74LCX373MTCX delivers superior speed and low-voltage efficiency in 3.3V domains but lacks 5V operational capability - making SN74HC373NSR the optimal general-purpose choice for mixed-voltage industrial interfaces.

Availability

SN74HC373NSR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, microcontroller parallel bus interfacing, and legacy peripheral bus buffering requiring stable component supply, long-term lifecycle support, and RoHS-compliant surface-mount packaging.

Supply support for SN74HC373NSR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with decades of heritage in high-reliability logic families.

The SN74HC373NSR belongs to TI's industry-standard 74HC logic series, designed specifically for robust, low-power, wide-supply-range digital interfacing in industrial control, instrumentation, and embedded computing applications.

FAQ

What is the maximum clock frequency supported by SN74HC373NSR?

The SN74HC373NSR does not operate on a clock signal - it is a transparent latch controlled by level-sensitive LE and OE inputs. Its usable data rate depends on timing parameters: minimum LE pulse width is 14ns at 6V, and setup/hold times are 9ns/10ns. This supports reliable operation in systems with effective data strobe frequencies up to ~35MHz, assuming proper PCB layout and load capacitance ≤50pF. The SN74HC373NSR datasheet specifies no maximum clock frequency because it has no internal clock.

Can SN74HC373NSR drive a 50pF capacitive load at 6V while meeting all specifications?

Yes - the SN74HC373NSR is characterized and guaranteed to meet all electrical and timing specifications (including tpd = 13ns, ten = 14ns, tdis = 13ns) when driving a 50pF capacitive load at VCC = 6V and TA = 25°C. The datasheet explicitly defines switching characteristics under CL = 50pF conditions. Exceeding 50pF increases propagation delay and may violate timing margins, especially at higher temperatures or supply voltages.

What happens to the outputs of SN74HC373NSR when OE is high and LE is toggled?

When OE is high, all eight Q outputs of the SN74HC373NSR enter high-impedance (Hi-Z) state regardless of LE state - no current flows, and outputs float electrically. Toggling LE while OE is high has no effect on output voltage or current; internal latches continue storing their last captured D-input values, but those states are not reflected at the pins. Only when OE is pulled low do the stored latch states appear at Q outputs.

Is SN74HC373NSR compatible with 3.3V microcontroller GPIOs driving its D and LE inputs?

Yes - the SN74HC373NSR has CMOS input thresholds (VIH = 3.15V min at VCC = 4.5V, VIL = 1.35V max), making it fully compatible with 3.3V microcontroller GPIOs when VCC = 5V. A 3.3V logic HIGH exceeds the 3.15V VIH threshold with margin, and a 3.3V logic LOW stays well below the 1.35V VIL threshold. No level-shifting circuitry is required for control signal interfacing.

Does SN74HC373NSR require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs (D1–D8, LE, OE) of the SN74HC373NSR must be terminated to either VCC or GND to prevent floating nodes, which can cause excessive ICC, erratic output behavior, or ESD susceptibility. TI recommends 10kΩ pull-up or pull-down resistors for unused inputs. Leaving inputs unconnected violates recommended operating conditions and risks undefined operation - this applies equally to SN74HC373NSR and all members of the 74HC family.