Analog Devices Inc./Maxim Integrated DS2176+

Overview

DS2176+ from Maxim Integrated (formerly Dallas Semiconductor) is a low-power CMOS T1 receive buffer IC designed to synchronize loop-timed T1 PCM data streams (1.544 MHz) to system-side timing while extracting and supervising robbed-bit ABCD signaling. It features a 2-frame (386-bit) FIFO buffer, slip-compensated multiframe sync (SMSYNC), open-collector SLIP output active-low for 65 SYSCLK cycles, and supports both 193S and 193E framing modes. Used in digital cross-connects and PABX-to-computer interfaces.

For engineers reviewing the DS2176+ datasheet, DS2176+ pinout, DS2176+ application, or DS2176+ equivalent, key selection considerations include its dual-clock compatibility (1.544/2.048 MHz via SCLKSEL), signaling freeze behavior under alarm/slip, serial/parallel backplane interface flexibility (S/P pin), and industrial-grade temperature support in DS2176N variant.

Technical Context

The DS2176+ implements a deterministic 2-frame deep FIFO with real-time buffer depth monitoring via RMSYNC–SMSYNC edge spacing. Slip detection triggers automatic recentering on frame boundaries and asserts SLIP for exactly 65 SYSCLK cycles - no partial-frame slips occur.

Signaling supervision uses configurable integration (SM0/SM1) across 1–5 multiframes and enforces freeze during slip or external SIGH assertion. Robbed-bit extraction is framed by FMS (193S/193E), and signaling updates are strictly synchronized to SMSYNC rising edges - never mid-multiframe.

Key Specifications

Pinout & Package

DS2176+ is packaged in a 24-pin 300-mil DIP (dual in-line package) with 0.3-inch width and standard through-hole footprint. Pin assignments are validated per DS2176 datasheet Rev. 06/13/97.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar T1 receive buffer applications.

Compared with DS2176+, DS2176N+ offers identical electrical and functional behavior with broader thermal qualification, while DS2180A+ integrates line-driver capability but requires redesign of analog front-end and power delivery - neither is pin-compatible with DS2176+.

Availability

DS2176+ is available at Aetrix Electronics and suitable for digital cross-connect systems, PABX-to-computer interfaces, and T1 trunk equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for DS2176+ 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

Maxim Integrated (acquired by Analog Devices in 2021) is a semiconductor company specializing in precision analog, mixed-signal, and high-reliability interface solutions for communications infrastructure.

The DS2176+ belongs to Maxim's legacy T-carrier interface product line, engineered specifically for robust T1/E1 receive-side synchronization and robbed-bit signaling supervision in telecom access and switching equipment.

FAQ

What is the primary function of the DS2176+ in a T1 system?

The DS2176+ performs two core functions: (1) synchronizing loop-timed T1 PCM data (1.544 MHz) to a system-side clock domain using a 2-frame FIFO buffer, and (2) extracting, buffering, and supervising robbed-bit ABCD signaling embedded in the T1 stream. It delivers slip-compensated signaling outputs (SMSYNC, A/B/C/D) and maintains frame-aligned serial output (SSER) - all critical for interoperability between line-side and backplane-side logic in DS2176+ implementations.

Does the DS2176+ support both T1 and E1 clock rates?

Yes, the DS2176+ supports both 1.544 MHz (T1) and 2.048 MHz (E1) system clock rates. Selection is controlled by the SCLKSEL pin: tied low for 1.544 MHz operation, high for 2.048 MHz. Internal logic adjusts slip detection criteria and F-bit handling accordingly - in 1.544 MHz mode, the F-bit passes through SSER; in 2.048 MHz mode, it is dropped and channel 1 MSB appears one bit later. This dual-rate capability is explicitly confirmed in DS2176+ datasheet AC characteristics and clock select section.

How does the DS2176+ handle signaling during a frame slip?

During a frame slip, the DS2176+ asserts SLIP (active-low, open-collector) for exactly 65 SYSCLK cycles and freezes signaling updates - holding A/B/C/D outputs constant and asserting SIGFRZ high. Signaling resumes only after the slip completes and the next SMSYNC rising edge occurs. Integration is limited to two multiframes during slip conditions to minimize delay, as documented in DS2176+ signaling supervision timing diagrams and Table 2 notes.

What is the role of the S/P pin on the DS2176+?

The S/P (Serial/Parallel Select) pin configures the DS2176+ for either serial or parallel backplane interfacing: tied to VSS for parallel operation (enabling look-ahead output timing), or to VDD for serial operation. In parallel mode, data appears at SSER eight clocks earlier than in serial mode - a hardware-level timing optimization that eliminates need for external pipeline registers in parallel TDM architectures using DS2176+.

Is the DS2176+ pin-compatible with the DS2176Q or DS2176N variants?

No - DS2176+ refers to the base commercial-grade 24-pin DIP version. DS2176Q is a 28-pin PLCC surface-mount variant with different pinout and package dimensions; DS2176N is the same 24-pin DIP package but rated for –40°C to +85°C operation. All share identical logic, timing, and signal functionality, but DS2176Q requires PCB redesign due to different pin mapping and footprint - DS2176+ and DS2176N are mechanically and electrically interchangeable.