Analog Devices Inc./Maxim Integrated DS2176QN

Overview

DS2176QN from Maxim Integrated (now Analog Devices) 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 detection on frame boundaries, open-collector SLIP output active low for 65 SYSCLK cycles, and supports both 193S and 193E framing modes via FMS pin. Used in digital cross-connects and PABX-to-computer interfaces.

For engineers reviewing the DS2176QN datasheet, DS2176QN pinout, DS2176QN application, or DS2176QN equivalent, key selection criteria include its dual-clock compatibility (1.544/2.048 MHz), signaling freeze control via SIGFRZ, external buffer recentering via ALN, and explicit support for serial/parallel backplane interfacing with S/P select.

Technical Context

The DS2176QN implements a 2-frame deep FIFO with real-time buffer depth monitoring via RMSYNC–SMSYNC edge spacing. Slip correction occurs only at frame boundaries, and the device enforces signaling update inhibition during alarm or slip conditions using internal freeze logic tied to SM0/SM1 configuration.

It extracts ABCD bits from T1 frames-A/B in 193S (FMS=0), A/B/C/D in 193E (FMS=1)-and integrates them across 1–5 multiframes depending on SM0/SM1 settings. Signaling updates are slip-compensated and synchronized to SMSYNC rising edges, with SBIT8 providing LSB timing for reinsertion into outgoing streams.

Key Specifications

Pinout & Package

DS2176QN is packaged in a 24-pin 300-mil DIP (dual in-line package) with through-hole mounting, rated for industrial temperature operation (–40°C to +85°C). Pin numbering follows standard DIP layout with Pin 1 at top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS2176Q, DS2176QN offers extended thermal operation critical for outdoor cabinets and uncooled enclosures; compared with DS2180A, DS2176QN provides lower power, smaller footprint, and design flexibility when transmit functionality is handled separately.

Availability

DS2176QN is available at Aetrix Electronics and suitable for digital cross-connect systems, PABX-to-computer interfaces, and T1 trunk aggregation requiring stable component supply, long-term lifecycle support, and industrial temperature performance.

Supply support for DS2176QN 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

Analog Devices (formerly Maxim Integrated) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for communications, industrial, and automotive markets.

The DS2176QN belongs to Maxim's legacy T-carrier interface product line, engineered specifically for telecom infrastructure applications requiring precise T1 receive synchronization, robbed-bit signaling supervision, and industrial-grade reliability.

FAQ

What is the primary function of the DS2176QN in a T1 system?

The DS2176QN serves as a receive-side T1 buffer that synchronizes loop-timed 1.544 MHz PCM data to system clock domains while extracting and supervising robbed-bit ABCD signaling. Its 2-frame FIFO ensures slips occur only at frame boundaries, and it delivers slip-compensated signaling updates via SMSYNC-making DS2176QN essential for deterministic timing in digital cross-connects and PABX interfaces.

How does the DS2176QN handle different T1 framing standards?

The DS2176QN supports both 193S and 193E framing via the FMS pin: FMS=0 selects 193S (A/B signaling only), FMS=1 selects 193E (A/B/C/D signaling). Signaling bit positions are fixed per standard-A in frame 6, B in frame 12 for 193S; C in frame 18, D in frame 24 for 193E-and DS2176QN outputs valid A/B/C/D signals accordingly, with C/D holding prior multiframe data in 193S mode.

What is the role of the SLIP output on the DS2176QN?

The SLIP output on DS2176QN is an active-low, open-collector signal asserted for exactly 65 SYSCLK cycles whenever the 2-frame buffer underflows or overflows. It provides a hardware-level slip event indicator for system-level fault handling, enabling external logic to pause processing, log events, or trigger recovery-without requiring software polling of internal status registers, since DS2176QN has no serial interface or status register.

Can the DS2176QN operate with a 2.048 MHz system clock?

Yes, the DS2176QN supports 2.048 MHz system clock operation when SCLKSEL is tied high. In this mode, the F-bit is dropped from the output stream, and the MSB of channel 1 appears at SSER one bit period after SFSYNC rising edge. Buffer slip criteria are adjusted internally to accommodate faster read rates, ensuring robust synchronization-confirming DS2176QN's dual-rate capability for E1/T1 hybrid systems.

How does the DS2176QN manage signaling updates during alarm conditions?

The DS2176QN freezes ABCD signaling updates during alarm or slip conditions using internal logic that holds previous values at outputs A/B/C/D and asserts SIGFRZ high. This freeze duration is configurable via SM0/SM1 (1–5 multiframes), and forcing SIGH low externally also triggers freeze. DS2176QN ensures signaling integrity by preventing corruption from transient line faults-critical for DS2176QN deployments in mission-critical telecom infrastructure where false signaling could disrupt call control.