Texas Instruments SN75477D

Overview

SN75477D from Texas Instruments is a dual NAND peripheral driver IC designed for high-voltage, high-current switching in electromechanical interface circuits. It delivers 300 mA continuous output current per channel, supports 100 V typical output breakdown voltage, features integrated clamp diodes for inductive transient suppression, and operates across 0°C to 70°C - making it suitable for relay, solenoid, and hammer-driver applications.

For engineers reviewing the SN75477D datasheet, SN75477D pinout, SN75477D application, or SN75477D equivalent, this page provides verified functional identity, SOIC-8 package mapping, confirmed NAND logic behavior, absolute maximum ratings, thermal derating data, and two validated alternative parts with documented functional and application differences.

Technical Context

The SN75477D implements two independent open-collector NAND drivers with PNP transistor inputs that reduce input current demand and enable TTL- or MOS-compatible operation. Each channel includes diode-clamped inputs and high-voltage clamp diodes rated for 300 mA/70 V transient suppression.

It is characterized for 0°C to 70°C operation with supply voltage limited to 4.5–5.5 V, exhibits propagation delays of 200–350 ns, and avoids latch-up at 55 V after conducting 300 mA - confirming robustness in inductive load switching environments.

Key Specifications

Pinout & Package

SN75477D is housed in an 8-pin SOIC (D) package with 1.27 mm lead pitch, 3.9 mm body width, and 1.75 mm max height - compatible with standard surface-mount assembly processes and IPC-7351 land patterns.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual NAND peripheral driver applications.

Compared with SN75477P, SN75477D offers surface-mount compatibility and tighter thermal resistance; compared with ULN2003A, SN75477D provides superior transient protection via its dedicated CLAMP pin and lower saturation voltage under 300 mA, but supports only two channels.

Availability

SN75477D is available at Aetrix Electronics and suitable for industrial relay interfaces, electromechanical printer subsystems, and solenoid actuator control requiring stable component supply across extended product lifecycles.

Supply support for SN75477D 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic products with broad industrial and automotive qualification.

The SN75477D belongs to TI's legacy dual peripheral driver family designed specifically for robust, high-voltage electromechanical interfacing in commercial-grade office and industrial equipment.

FAQ

What logic function does the SN75477D implement?

The SN75477D implements two independent NAND gates with active-low enable: each output Y = NOT(A AND S). When S is low, the output follows the inverse of A; when S is high, both outputs enter high-impedance state. This behavior is confirmed in the device's function table and logic diagrams in SLRS025A, and applies identically to all variants including SN75477D.

Does the SN75477D require external flyback diodes when driving inductive loads?

No - the SN75477D integrates output clamp diodes rated for 300 mA and 70 V reverse voltage. When the CLAMP pin is connected to a positive supply (e.g., +55 V), these diodes provide a safe path for inductive kickback energy. External diodes are unnecessary unless operating beyond the specified 70 V clamp threshold.

What is the purpose of the CLAMP pin on the SN75477D?

Pin 8 (CLAMP) is the anode connection for the internal output clamp diodes. It must be tied to a positive voltage rail (up to +55 V) to provide a return path for inductive transient current. Without this connection, the clamp diodes cannot function, exposing outputs to destructive voltage spikes during coil turn-off.

Can the SN75477D operate from a 3.3 V supply?

No - the SN75477D is specified only for 4.5 V to 5.5 V operation. Its TTL/MOS-compatible inputs require ≥2 V high-level input voltage and ≤0.8 V low-level input voltage, and internal PNP input structure is optimized for 5 V biasing. Operation below 4.5 V risks incomplete logic transitions and reduced output current capability.

Is the SN75477D pin-compatible with the SN75476D or SN75478D?

Yes - SN75476D (AND), SN75477D (NAND), and SN75478D (OR) share identical SOIC-8 pinouts, package dimensions, and electrical interfaces. Only the internal logic function differs; all three support the same VCC, CLAMP, GND, and I/O pin assignments, enabling direct functional substitution with logic-level adjustment.