Analog Devices Inc./Maxim Integrated DS21552LB

Overview

DS21552LB from Maxim Integrated is a 5V single-chip T1 transceiver supporting DS1/ISDN-PRI/J1 line interface, long- and short-haul LIU operation, crystal-less jitter attenuation (32/128-bit selectable), DSX-1 and CSU line build-outs (–7.5dB/–15dB/–22.5dB), and HDLC controller with 64-byte buffers configurable for FDL or DS0. It serves in telecom access equipment requiring ANSI T1.403-1995, ITU G.703/G.704 compliance.

For engineers reviewing the DS21552LB datasheet, DS21552LB pinout, DS21552LB application, or DS21552LB equivalent, key selection considerations include its 100-pin LQFP package, independent transmit/receive elastic stores synchronized to asynchronous backplanes up to 8.192 MHz, IEEE 1149.1 JTAG boundary scan support, and programmable in-band loop code generation/detection (1–8 bits).

Technical Context

The DS21552LB integrates full T1 framer, line interface unit (LIU), jitter attenuator, HDLC controller, and dual elastic stores - all operating independently on transmit and receive paths. Its clock recovery supports cable lengths from 0 to >6000 ft, and it synthesizes an 8.192 MHz output locked to RCLK while accepting 1.544 MHz or 2.048 MHz RSYSCLK inputs.

It implements hardware-based signaling with reinsertion into backplane multiframe sync, supports D4 (SLC-96) and ESF framing, and provides per-channel loopback, idle code insertion, and alarm detection (RCL, RLOS, RRA, RAIS) with state-change interrupts. The parallel control port supports Intel/Motorola bus protocols, muxed or non-muxed.

Key Specifications

Pinout & Package

DS21552LB is housed in a 100-pin LQFP package (14 mm × 14 mm), RoHS-compliant, with separate analog (RVDD/TVDD) and digital (DVDD) supply domains, dedicated ground planes (RVSS/TVSS/DVSS), and IEEE 1149.1 JTAG test access pins.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21552LB, DS21552L lacks industrial temperature support but shares identical electrical and functional behavior, while DS21352LN offers voltage and power advantages at the cost of supply-domain compatibility - making DS21552LB the sole choice for legacy 5V, wide-temperature T1 line cards.

Availability

DS21552LB is available at Aetrix Electronics and suitable for telecom infrastructure, channel bank design, and ISDN PRI gateway development requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for DS21552LB 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and RF solutions for communications, industrial, and automotive markets.

The DS21552LB belongs to Maxim's SCT (Single-Chip Transceiver) product line, engineered specifically for carrier-class T1/E1 line interface applications demanding full standards compliance, low-jitter timing, and hardware-accelerated signaling processing.

FAQ

What is the operating voltage range for DS21552LB?

The DS21552LB operates from a nominal 5V supply with ±5% tolerance (4.75V to 5.25V). This 5V specification distinguishes it from the 3.3V DS21352LN variant and ensures compatibility with legacy telecom power architectures. All digital I/Os are 5V-tolerant, and analog supplies (RVDD, TVDD, DVDD) must be independently regulated per datasheet recommendations to maintain noise immunity and jitter performance in the DS21552LB.

Does DS21552LB support both D4 and ESF framing formats?

Yes, DS21552LB fully supports both D4 (Superframe) and ESF (Extended Superframe) framing structures. Its framer automatically detects and locks to either format, locates frame/multiframe boundaries, extracts and inserts robbed-bit signaling (for D4) or FDL data (for ESF), and monitors alarms including RLOS, RRA, and RAIS. This dual-format capability is confirmed in the device description and functional block diagram, making DS21552LB suitable for migration from legacy D4 networks to modern ESF deployments.

Can DS21552LB generate and detect in-band loop codes?

Yes, DS21552LB includes a programmable in-band loop code generator and detector capable of handling codes 1–8 bits in length, including AT&T TR62411 CSU-compliant sequences. This functionality is implemented in dedicated registers (e.g., LCR, LCR2) and operates independently on transmit and receive paths. Loop code detection triggers status flags and can assert the INT* pin, enabling automated line diagnostics without host CPU polling - a core capability documented in Sections 17 and 7 of the DS21552LB datasheet.

Is DS21552LB pin-compatible with earlier Maxim T1 transceivers?

Yes, DS21552LB is explicitly stated as pin-compatible with DS2152, DS2154, DS21354, and DS21554 single-chip transceivers. This compatibility extends to mechanical footprint, signal assignment, and power pin mapping in the 100-pin LQFP package. However, software initialization may require minor updates to leverage new features like interleaved PCM bus operation or JTAG boundary scan - as noted in the "NEW FEATURES (after the DS2152)" section of the DS21552LB datasheet.

What clock frequencies does DS21552LB accept on RSYSCLK and TSYSCLK?

DS21552LB accepts RSYSCLK and TSYSCLK inputs at 1.544 MHz, 2.048 MHz, or bursty clocks up to 8.192 MHz - enabling elastic store synchronization to common telecom backplane rates. The 8.192 MHz capability is critical for interleaved PCM bus operation, where multiple T1 channels share a time-division multiplexed data path. This specification is validated in Section 24.3 (Receive Side AC Characteristics) and Figure 21-4/21-5 of the DS21552LB datasheet, confirming operational margin beyond nominal rates.