Analog Devices Inc./Maxim Integrated DS2176

Overview

DS2176 from Dallas Semiconductor (now Maxim Integrated) 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, extract and supervise robbed-bit ABCD signaling, and provide slip-compensated multiframe alignment. It features a 2-frame (386-bit) buffer, 24-pin DIP or 28-pin PLCC package, industrial temperature range (–40°C to +85°C for DS2176N), and compatibility with DS2180A transceivers in digital trunk and cross-connect applications.

For engineers reviewing the DS2176 datasheet, DS2176 pinout, DS2176 application, or DS2176 equivalent, key selection considerations include frame-slip handling at boundary-aligned intervals, robbed-bit signaling extraction under 193S/193E framing, dual-clock support (1.544/2.048 MHz), open-collector SLIP output timing (65 SYSCLK cycles), and signaling freeze behavior during alarm conditions.

Technical Context

The DS2176 implements a dual-clock, dual-domain synchronization architecture: RCLK (1.544 MHz) clocks incoming serial data on its falling edge, while SYSCLK (1.544 or 2.048 MHz) controls system-side output timing on its rising edge. Buffer depth is monitored in real time via RMSYNC–SMSYNC phase relationship, triggering frame slips only at multiframe boundaries when the 2-frame buffer empties or fills completely.

Signaling supervision uses configurable integration (SM0/SM1-selectable 1–5 multiframes) and freeze logic: SIGFRZ asserts high during internal slip or external SIGH assertion, holding A/B/C/D outputs at prior state until SMSYNC rising edge. Signaling updates occur once per multiframe, synchronized to SMSYNC, with SBIT8 enabling reinsertion of extracted bits into outgoing streams.

Key Specifications

Pinout & Package

DS2176 is available in 24-pin 300-mil DIP (dual in-line package) and 28-pin PLCC (plastic leaded chip carrier) variants. The DS2176N designation refers to the industrial-temperature version in either package.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS2180A and MC145508, the DS2176 delivers optimized, standalone T1 receive buffering with superior signaling supervision granularity (per-multiframe freeze, configurable integration), minimal footprint (24-pin DIP), and guaranteed industrial temperature operation in DS2176N form-making it ideal for embedded telecom infrastructure where reliability and signaling fidelity outweigh multi-standard flexibility.

Availability

DS2176 is available at Aetrix Electronics and suitable for digital trunk interfaces, T1 drop-and-insert equipment, and digital cross-connect systems requiring stable component supply, long-lifecycle availability, and industrial-temperature performance.

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

Dallas Semiconductor, now part of Maxim Integrated (acquired 2001), specialized in precision timing, data communications, and mixed-signal interface ICs for telecom and industrial applications.

The DS2176 belongs to Dallas' T1/E1 interface product line, engineered specifically for robust receive-side synchronization and robbed-bit signaling supervision in carrier-class digital telephony equipment.

FAQ

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

The DS2176 serves as a receive-side T1 buffer and signaling supervisor. Its core functions are synchronizing loop-timed T1 PCM data (1.544 MHz) to system-side timing using a 2-frame buffer, and extracting, freezing, and integrating robbed-bit ABCD signaling embedded in the data stream. In the DS2176, these operations occur independently of transmit functions, making it ideal for receive-only applications such as digital trunk termination and PABX interfaces where signaling integrity is critical.

How does the DS2176 handle frame slips, and what is the role of the SLIP pin?

The DS2176 detects buffer underflow or overflow and triggers a frame slip only at multiframe boundaries to preserve data integrity. When a slip occurs, the SLIP pin-a dedicated active-low open-collector output-is pulled low for exactly 65 SYSCLK cycles. This precise timing allows external logic to detect and respond to slips deterministically. In the DS2176, SLIP assertion coincides with automatic buffer recentering and signaling freeze via SIGFRZ, ensuring no corrupted signaling updates during resynchronization.

What framing standards does the DS2176 support, and how is framing selected?

The DS2176 supports both 193S (D4) and 193E (extended) T1 framing formats. Framing selection is controlled by the FMS (Frame Mode Select) pin: tying FMS low selects 193S framing (A/B signaling in frames 6 and 12), while tying FMS high selects 193E framing (A/B/C/D signaling in frames 6, 12, 18, and 24). This hardware-selectable configuration ensures compatibility with North American (193S) and international (193E) T1 infrastructure without firmware changes. The DS2176 maintains correct signaling mapping and timing for both modes.

Can the DS2176 operate with both 1.544 MHz and 2.048 MHz system clocks, and how is clock selection managed?

Yes, the DS2176 supports both 1.544 MHz (T1) and 2.048 MHz (E1) system clock rates. Clock selection is controlled by the SCLKSEL pin: tying SCLKSEL low configures the device for 1.544 MHz operation (passing the F-bit through SSER), while tying it high configures 2.048 MHz operation (dropping the F-bit and shifting MSB timing). The DS2176 adjusts its internal slip-detection logic and output timing accordingly-ensuring correct buffering, signaling alignment, and SBIT8 positioning for each clock domain without external reconfiguration.

What is the purpose of the SIGFRZ and SIGH pins in the DS2176, and how do they interact?

SIGFRZ is an output that goes high whenever signaling updates to A/B/C/D are frozen-either due to an internal slip condition or external assertion of the SIGH input. SIGH is an input that, when driven low, forces immediate signaling freeze regardless of buffer state. In the DS2176, this interaction provides deterministic control over signaling stability: during alarms or maintenance events, asserting SIGH guarantees stale but consistent signaling data is held, while SIGFRZ provides feedback to system logic that updates are suspended. Both functions are fully supported across all framing and clock modes.