Texas Instruments DS3680N

Overview

DS3680N from Texas Instruments is a quad telephone relay driver IC designed to interface –48-V relay systems with TTL/CMOS logic in telecom central office and line card applications. It delivers 50-mA output current per channel from –52-V battery supply, features ±20-V common-mode input range referenced to battery ground, built-in clamp diodes, and fail-safe disconnect via complementary inputs.

For engineers reviewing the DS3680N datasheet, DS3680N pinout, DS3680N application, or DS3680N equivalent, key selection criteria include –52-V battery compatibility, high-impedance differential inputs, inductive load handling up to 5 H, low off-state battery current (–100 µA), and PDIP-14 packaging for through-hole telecom board assembly.

Technical Context

The DS3680N implements four independent high-side relay drivers with differential input pairs (IN+, IN–) and open-collector outputs referenced to BAT NEG. Each driver uses internal clamping to suppress relay coil flyback transients up to ±1.2 V and ensures fail-safe off-state when either input is open.

Its architecture supports wide common-mode input operation (–20 V to +20 V vs. BAT GND), enabling direct connection to diverse signaling sources-including negative logic, grounded logic, or floating battery-referenced controls-without level-shifting circuitry.

Key Specifications

Pinout & Package

DS3680N is housed in a 14-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width and through-hole mounting. Pin 1 is marked by a notch or dot; leads are tin-lead (NIPDAU) finished and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS3680D and SN75LBC176, the DS3680N uniquely combines through-hole PDIP-14 packaging, –52-V relay driving capability, and fail-safe differential inputs - making it the only viable option for repairing or maintaining legacy telecom hardware without board modification.

Availability

DS3680N is available at Aetrix Electronics and suitable for central office line cards, digital loop carrier systems, and legacy PBX interface modules requiring stable component supply and long-term obsolescence management.

Supply support for DS3680N 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 founded in 1930, delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The DS3680N belongs to TI's legacy telecom interface product line, engineered specifically for robust, fail-safe relay control in –48-V/–52-V telephone infrastructure equipment operating from 0°C to 70°C.

FAQ

What is the maximum inductive load the DS3680N can drive?

The DS3680N is rated for inductive loads up to 5 H at 50 mA, as specified in its Absolute Maximum Ratings table. This capacity covers standard electromechanical telephone relays used in central office and line card applications. The integrated clamp diode limits flyback voltage to ±1.2 V, protecting both the DS3680N and surrounding circuitry during coil de-energization. Always verify relay coil inductance and resistance against DS3680N's VO(on) and thermal limits in final design.

Does the DS3680N require external flyback diodes?

No, the DS3680N includes built-in output clamp diodes that suppress relay coil flyback transients, eliminating the need for external diodes. Its VOK specification guarantees clamp voltage of ±0.9 V to ±1.2 V at ±50 mA, ensuring safe energy dissipation. This integration reduces bill-of-materials cost and PCB footprint - critical in space-constrained telecom line cards where the DS3680N is commonly deployed.

Is the DS3680N pin-compatible with older National Semiconductor or Fairchild versions?

Yes, the DS3680N is a direct replacement for National Semiconductor DS3680 and Fairchild µA3680, sharing identical pinout, electrical specifications, and functional behavior. TI explicitly states this compatibility in the device description. No PCB changes are required when upgrading or replacing these legacy parts with DS3680N in existing through-hole telecom hardware.

What is the purpose of the complementary IN+ and IN– inputs on the DS3680N?

The complementary IN+ and IN– inputs implement a differential control scheme that ensures fail-safe operation: if either input opens or becomes disconnected, the driver output defaults to the off state, preventing unintended relay closure. This design is critical in telecom infrastructure where reliability and safety are paramount. The DS3680N leverages this feature across all four channels to maintain system integrity during wiring faults or connector failures.

Can the DS3680N operate with logic ground separated from battery ground?

Yes, the DS3680N is explicitly designed for ground separation: its inputs reference BAT GND, not logic ground, and support a ±20-V common-mode input range relative to BAT GND. This architecture accommodates IR drop and noise between logic and battery domains - a common challenge in large telecom cabinets. The DS3680N thus enables robust interfacing between low-voltage controllers and –52-V relay banks without level shifters or isolators.