Analog Devices Inc./Maxim Integrated DS2187+

Overview

DS2187+ from Maxim Integrated (now part of Analog Devices) is a T1/CEPT receive line interface IC that extracts clock and data from twisted-pair or coaxial transmission lines. It supports 1.544 MHz (T1) and 2.048 MHz (CEPT) primary-rate networks, features on-chip precision PLL with laser-trimmed VCO, decodes AMI/B8ZS/HDB3, and operates from a single 5V supply. Used in CSU, DACS, channel banks, and PABX-to-computer interfaces.

For engineers reviewing the DS2187+ datasheet, DS2187+ pinout, DS2187+ application, or DS2187+ equivalent, key selection considerations include its dual-standard support (T1/CEPT), integrated jitter-tolerant clock recovery, alarm reporting (AIS/RCL/BPV), zero external crystal requirement, and compatibility with DS2180A/DS2181A transceivers and DS2186/DS2188 companion devices.

Technical Context

The DS2187+ employs a hybrid frequency-locked loop (FLL) and digital phase-locked loop (DPLL) architecture: the high-Q FLL tracks average incoming frequency (±6% capture range, 50 Hz loop bandwidth), while the DPLL handles jitter tracking using programmable divide ratios (÷11/12/13) off 18.528 MHz (T1) or 24.576 MHz (CEPT) internal VCO clocks. This enables compliance with TR 62411 and G.823 jitter specifications.

Signal acquisition begins with peak detection at RTIP/RRING inputs (minimum 0.6 V_pk threshold), followed by 50% slicer decisioning. Code suppression (ZCSEN) selectively replaces B8ZS/HDB3 codewords with all-zeros, and alarm logic monitors AIS (via RAIS timing), RCL (192 consecutive zeros), and BPV (bipolar violations), with outputs synchronized to RCLK.

Key Specifications

Pinout & Package

DS2187+ is available in two industry-standard packages: 18-pin DIP (300-mil) and 20-pin SOIC (300-mil). Both variants share identical pin functions but differ in pin count due to NC assignments - the SOIC version adds two no-connect pins (pins 4 and 17).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar T1/CEPT receive line interface applications.

Compared with DS2187S and DS2180A, the DS2187+ offers the most direct fit for dedicated, low-jitter receive termination - its single-function architecture delivers superior lock stability and lower component count than transceiver alternatives, while its DIP/SOIC dual packaging supports both legacy through-hole and modern SMT production.

Availability

DS2187+ is available at Aetrix Electronics and suitable for channel banks, CSUs, DACS systems, and PABX-to-computer interfaces requiring stable component supply, long-lifecycle support, and compliance with North American and European telecom standards.

Supply support for DS2187+ 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, now part of Analog Devices, is a semiconductor company specializing in high-performance analog, mixed-signal, and power management solutions for communications, industrial, and computing markets.

The DS2187+ belongs to Maxim's telecom line interface product line, designed specifically for carrier-class T1 and CEPT physical layer receive termination with integrated clock recovery, alarm reporting, and standard-compliant decoding.

FAQ

What is the primary function of the DS2187+ in a T1/CEPT system?

The DS2187+ serves as a dedicated receive line interface IC that extracts clock and data from T1 (1.544 MHz) or CEPT (2.048 MHz) transmission lines. It performs AMI/B8ZS or AMI/HDB3 decoding, generates synchronized RCLK and RPOS/RNEG outputs, and reports alarms including AIS, RCL, and BPV - all without requiring external crystals or tuning components. Its role is strictly receive-side physical layer termination.

How does the DS2187+ achieve jitter-tolerant clock recovery?

The DS2187+ uses a dual-loop architecture: a high-Q frequency-locked loop (FLL) tracks the average line frequency (±6% capture range, 50 Hz bandwidth), while a digital phase-locked loop (DPLL) handles short-term jitter using programmable divide ratios (÷11/12/13) off an internal laser-trimmed VCO (18.528 MHz for T1, 24.576 MHz for CEPT). This combination meets AT&T TR 62411 and CCITT G.823 jitter specifications, with 200 UI input tolerance at 10 Hz.

What are the key differences between DS2187+ and DS2187S?

The DS2187+ and DS2187S share identical silicon and electrical specifications, but differ in packaging: DS2187+ is offered in both 18-pin DIP and 20-pin SOIC variants, whereas DS2187S refers exclusively to the 20-pin SOIC version. The SOIC variant adds two no-connect pins (4 and 17), and is optimized for surface-mount assembly. Functionally, both operate identically when configured for the same T1/CEPT mode via RCLKSEL.

Can the DS2187+ be used without an external crystal or oscillator?

Yes - the DS2187+ integrates a laser-trimmed voltage-controlled oscillator (VCO) that provides the precise 18.528 MHz (T1) or 24.576 MHz (CEPT) reference frequencies required for clock recovery. This eliminates the need for external crystals, LC tanks, or crystal oscillators, reducing component count, board space, and calibration effort. The only external passive required is a 10 µF capacitor on the LCAP pin for loop filter stability.

What alarm conditions does the DS2187+ monitor and report?

The DS2187+ monitors and reports three standardized alarm conditions: AIS (Alarm Indication Signal) triggered when fewer than three zeros appear in two RAIS periods; RCL (Receive Carrier Loss) asserted after 192 consecutive zeros at RPOS/RNEG; and BPV (Bipolar Violation) pulsed for each bipolar violation detected - unless suppressed by ZCSEN during B8ZS/HDB3 decoding. All outputs are synchronous to RCLK and meet PUB 43801 and TR 62411 timing requirements.