Analog Devices Inc./Maxim Integrated DS21552L

Overview

DS21552L from Maxim Integrated is a 5V single-chip T1 transceiver supporting DS1/ISDN-PRI/J1 line interfaces, featuring crystal-less jitter attenuation (32- or 128-bit selectable), dual elastic store slip buffers for asynchronous backplanes up to 8.192 MHz, HDLC controller with 64-byte buffers configurable for FDL or DS0 operation, and full compliance with ANSI T1.403-1995, ITU G.703/G.704/G.706, and G.823 standards - deployed in carrier-grade CSU/DSU, channel banks, and TDM multiplexers.

For engineers reviewing the DS21552L datasheet, DS21552L pinout, DS21552L application, or DS21552L equivalent, key selection criteria include its 100-pin LQFP package, independent transmit/receive paths, programmable in-band loop code generation (1–8 bits), IEEE 1149.1 JTAG boundary scan support, and compatibility with both long-haul (CSU) and short-haul (DSX-1) line build-outs (-7.5 dB, -15 dB, -22.5 dB).

Technical Context

The DS21552L integrates a complete T1 framer, line interface unit (LIU), HDLC controller, and dual elastic stores - enabling simultaneous framing, signaling extraction/insertion (robbed-bit, FDL), and phase/frequency compensation between recovered T1 data (RCLK) and asynchronous backplane clocks (RSYSCLK/TSYSCLK up to 8.192 MHz). Its clock recovery circuitry supports cable lengths from 0 to over 6000 feet.

It implements hardware-based signaling reinsertion, signaling freeze, and interrupt-on-alarm-change (RCL, RLOS, RRA, RAIS), while decoupling line interface functions from framer logic to allow monitoring of bipolar data streams or integration with optical/HDSL NRZ interfaces. The 8.192 MHz clock output is synthesized and locked to RCLK.

Key Specifications

Pinout & Package

DS21552L is housed in a 100-pin LQFP package (14 mm × 14 mm), with separate analog receive/transmit supplies (RVDD/TVDD), dual ground domains (RVSS/TVSS/DVSS), and dedicated JTAG test access pins (JTMS, JTCLK, JTRST, JTDI, JTDO).

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS21552LN, DS21552L offers identical feature set at lower cost for commercial-temperature deployments; compared with DS2152, DS21552L delivers essential modern capabilities - including hardware signaling, elastic store, and JTAG - that reduce system-level firmware burden and improve testability.

Availability

DS21552L is available at Aetrix Electronics and suitable for carrier-grade CSU/DSU units, TDM channel banks, remote terminal multiplexers, and TDM-over-IP gateways requiring stable component supply across multi-year production cycles.

Supply support for DS21552L 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 precision analog, mixed-signal, and power management ICs for communications, industrial, and computing applications.

The DS21552L belongs to Maxim's SCT (Single-Chip Transceiver) product line, designed specifically for integrated T1/E1 line interface solutions in space-constrained, high-reliability telecom infrastructure equipment.

FAQ

What is the operating voltage requirement for DS21552L?

The DS21552L operates from a single 5V ±5% supply. It does not support 3.3V operation - that function is reserved for the pin-compatible DS21352L variant. All digital I/Os are 5V-tolerant, and analog sections (RVDD, TVDD) require clean, well-decoupled 5V rails per the layout guidelines in the datasheet. DS21552L must not be powered from mixed-voltage domains without level translation.

Does DS21552L support both D4 and ESF framing formats?

Yes, DS21552L natively supports both D4 superframe (12-frame multiframe) and ESF extended superframe (24-frame multiframe) structures. The framer automatically detects and locks to either format, extracts Fs/Ft signaling bits in D4 mode, and handles FPS and CRC6 in ESF mode - including Japanese CRC6 compliance per JIS C 5901. Configuration is register-controlled and runtime-switchable.

Can DS21552L generate and detect in-band loop codes without external logic?

Yes, DS21552L includes a dedicated programmable in-band loop code generator and detector capable of handling codes 1–8 bits in length, including AT&T-defined CSU loop codes. Detection triggers status register flags and optional INT* assertion; generation is controlled via registers and requires no host CPU intervention during loopback execution.

Is DS21552L pin-compatible with earlier Maxim T1 transceivers?

DS21552L is pin-compatible with DS2152, DS2154, DS21354, and DS21554 single-chip transceivers in the same 100-pin LQFP package. However, software compatibility is not guaranteed due to added registers and enhanced features (e.g., elastic store control, HDLC configuration, JTAG). Migration from DS2152 requires firmware updates but no PCB revision.

What clock frequencies does DS21552L support on its RSYSCLK and TSYSCLK inputs?

DS21552L supports RSYSCLK and TSYSCLK inputs at 1.544 MHz, 2.048 MHz, 4.096 MHz, and 8.192 MHz - enabling use in D4, E1, and interleaved PCM backplane architectures. The elastic stores synchronize to these clocks independently, allowing mismatched transmit/receive backplane rates. AC timing specifications for all four frequencies are provided in Section 24 of the datasheet.