Texas Instruments DS3668N

Overview

DS3668N from National Semiconductor is a quad fault-protected peripheral driver IC with open-collector NPN outputs, 70V breakdown voltage, 600 mA sink capability per channel, and integrated 12 µs fault detection with automatic shutdown and reset via input or enable toggle. It serves as a high-voltage, high-current interface between logic-level controllers and inductive loads such as relays and solenoids in industrial control systems.

For engineers reviewing the DS3668N datasheet, DS3668N pinout, DS3668N application, or DS3668N equivalent, key selection criteria include its 1.0 A fault threshold, 550 mV typical output ON voltage at 600 mA, built-in clamp diodes rated for 800 mA, fail-safe high-impedance state on open inputs, and compatibility with 5 V TTL/MOS logic sources.

Technical Context

The DS3668N implements four independent NPN output stages, each with dedicated current-sensing and delay-based fault protection circuitry that disables only the affected channel upon >1.0 A overload for >12 µs-preserving operation of remaining channels. Its TTL-compatible inputs draw just 1 µA typical, enabling direct drive from CMOS or microcontroller GPIOs without buffering.

Each output integrates a clamp diode (VF = 1.2–1.6 V @ 800 mA) to suppress inductive fly-back up to 35 V, preventing latch-up; the device guarantees glitch-free power-up/down behavior and enters high-impedance state if any input floats, ensuring safe default behavior in system initialization or failure modes.

Key Specifications

Pinout & Package

Molded 16-pin dual-in-line package (NS Package Number N16E), with four dedicated ground pins thermally bonded directly to the die via copper lead frame for enhanced power dissipation-rated 2 W at 25°C free-air.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN75437AN and ULN2803ADWR, the DS3668N uniquely delivers per-channel fault isolation with 12 µs response, sub-600 mV ON voltage, and thermally optimized 16-pin DIP packaging-making it optimal for mission-critical industrial interfaces where reliability, efficiency, and board-level integration are prioritized.

Availability

DS3668N is available at Aetrix Electronics and suitable for relay drivers, solenoid drivers, and stepping motor drivers requiring stable component supply, long-term lifecycle support, and consistent electrical performance across temperature extremes (−40°C to +125°C).

Supply support for DS3668N 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

National Semiconductor Corporation was a U.S.-based analog and mixed-signal semiconductor company acquired by Texas Instruments in 2011, known for high-reliability interface and power management ICs.

The DS3668N belongs to National's legacy peripheral driver family, engineered specifically for rugged industrial control applications demanding fault resilience, high-voltage tolerance, and direct logic-level interfacing without external protection circuitry.

FAQ

What is the maximum continuous output current per channel of the DS3668N?

The DS3668N supports 600 mA continuous sink current per output channel under specified thermal conditions. All four channels may conduct rated current simultaneously, provided average power dissipation remains within the 2075 mW limit at 25°C free-air-derating linearly to 1328 mW at 70°C. The DS3668N's thermal design with four GND pins helps sustain this rating in real-world PCB layouts.

Does the DS3668N require external fly-back diodes when driving inductive loads?

No, the DS3668N does not require external fly-back diodes for inductive loads operating ≤35 V. Each output integrates a clamp diode rated for 800 mA peak current and 1.2–1.6 V forward voltage. These on-chip diodes safely dissipate inductive energy during turn-off, eliminating the need for discrete components-confirmed in the DS3668N datasheet Figure 4 and Application Note AN-213.

How does the fault protection circuit in the DS3668N reset after activation?

The DS3668N fault protection circuit resets when either the corresponding input is toggled (e.g., from high to low or low to high) or the global EN pin is driven low for at least 1.0 µs. This reset mechanism is asynchronous and immediate-no power cycle or external timer is needed. The DS3668N truth table and Electrical Characteristics table explicitly define t_RL = 1.0 µs as the minimum low-time requirement for EN-based reset.

Is the DS3668N pin-compatible with the SN75437AN?

Yes, the DS3668N is pin-for-pin compatible with the SN75437AN, sharing identical pin numbering, package outline (N16E), and basic functional mapping. However, the DS3668N adds per-channel fault protection, integrated clamp diodes, and fail-safe open-input behavior-features absent in the SN75437AN. System-level replacement requires verifying that these enhancements align with design requirements.

What is the recommended supply voltage range for reliable operation of the DS3668N?

The DS3668N is specified for reliable operation from 3.0 V to 5.25 V DC on VCC. Operation below 3.0 V risks undefined logic thresholds and reduced output drive strength; above 5.25 V exceeds absolute maximum ratings and may cause permanent damage. The DS3668N datasheet Table "Operating Conditions" confirms this range, and all electrical characteristics-including VOL and ICC-are guaranteed only within it.