Analog Devices Inc./Maxim Integrated DS21Q48

Overview

DS21Q48 from Maxim Integrated is a quad-channel 5V E1/T1/J1 Line Interface Unit (LIU) in a 144-ball CSBGA package, supporting simultaneous long- and short-haul trunks with software-selectable 75Ω/100Ω/120Ω receive termination, AMI/HDB3/B8ZS encoding/decoding, and crystal-less jitter attenuation requiring only 2.048MHz or 1.544MHz master clock. It serves as the physical layer interface in telecom access equipment for E1/T1 line aggregation.

For engineers reviewing the DS21Q48 datasheet, DS21Q48 pinout, DS21Q48 application, or DS21Q48 equivalent, key selection criteria include quad-channel LIU integration, 5V-only operation, 144-pin CSBGA thermal performance (θJA = 19.5°C/W at 200 LFM), G.703/G.775 compliance, and support for both multiplexed/nonmultiplexed parallel and serial control interfaces.

Technical Context

The DS21Q48 implements four independent LIU channels sharing a common 5V supply and control bus, each featuring full analog front-end circuitry including transformer-coupled RTIP/RRING inputs, programmable receive sensitivity (–43dBm E1 / –36dBm T1), active filtering for nonlinear loss compensation, and bipolar/NRZ data I/O on TPOS/TNEG and RPOS/RNEG. Each channel integrates dedicated PLL-based clock/data recovery, selectable 32-/128-bit jitter attenuator FIFOs, and line build-out generation per G.703 (E1) and DSX-1/CSU (T1).

Control is implemented via 8-bit parallel (Intel/Motorola timing, muxed or nonmuxed), 3-wire serial (SDI/SDO/SCLK), or hardware mode (BIS0/BIS1), with register-mapped configuration of encoding schemes (AMI/HDB3/B8ZS), loopback types (local/remote/analog/dual), PRBS pattern generation/detection, and alarm detection (AIS, RCL, LOTC). All channels support synchronized backplane clock outputs (2.048–16.384MHz) derived from RCLK.

Key Specifications

Pinout & Package

DS21Q48 uses a 144-ball CSP Ball Grid Array (CSBGA) package measuring 17mm × 17mm with 0.8mm ball pitch. Thermal characteristics are specified in Table 9-4: θJA = 19.5°C/W at 200 LFM airflow, θJC = 3.5°C/W. Pin assignments are defined in Section 8 (Figure 8-1) and Table 8-1 of the datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar line interface unit applications.

Compared with DS2148GN and MAX3005, the DS21Q48 uniquely delivers four synchronized, carrier-grade E1/T1 interfaces with crystal-less jitter attenuation, full G.703 line build-out support, and thermal-optimized 144-ball CSBGA packaging - making it the sole option for high-density, standards-compliant telecom line cards.

Availability

DS21Q48 is available at Aetrix Electronics and suitable for telecom access gateways, DSLAM line cards, enterprise PBX trunk modules, and wireless backhaul radios requiring stable component supply and long-term lifecycle support.

Supply support for DS21Q48 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 industrial, communications, and computing applications.

The DS21Q48 belongs to Maxim's telecom line interface product line, designed specifically for carrier-class E1/T1/J1 physical layer interfacing in multi-channel access equipment requiring G.703/G.775 compliance and thermal reliability.

FAQ

What is the operating temperature range for the DS21Q48?

The DS21Q48 is rated for commercial temperature operation from 0°C to +70°C, as confirmed in the Ordering Information table. This distinguishes it from the industrial-grade DS21Q48N variant (-40°C to +85°C). The DS21Q48's thermal characteristics (θJA = 19.5°C/W at 200 LFM) are validated for this range and must be respected in thermal design to ensure reliable operation within specifications.

Does the DS21Q48 support 3.3V operation?

No, the DS21Q48 is a 5V-only device. Revision history notes explicitly state "Changes to datasheet to indicate 5V only part" (Rev 6, 011801) and "Corrected typos and removed instances of 3V operation" (Rev 9, 082504). VSM must be tied high, and VDD must be supplied with 5.0V ±5%; operation outside this range violates Absolute Maximum Ratings and may cause functional failure.

How many independent line interfaces does the DS21Q48 provide?

The DS21Q48 provides four fully independent E1/T1/J1 line interface units (LIUs) on a single die, as stated in the Ordering Information table and detailed in Section 8 ("DS21Q48 Quad LIU"). Each channel has dedicated RTIP/RRING, TTIP/TRING, RPOS/RNEG, TPOS/TNEG, and associated control registers - enabling true parallel line processing without resource contention.

What clock frequencies does the DS21Q48 support for jitter attenuation?

The DS21Q48 supports 2.048MHz master clock (MCLK) for both E1 and T1 operation, with optional 1.544MHz MCLK for T1-only applications. Its crystal-less jitter attenuator uses either 32-bit or 128-bit FIFO depth, and the recovered clock (RCLK) synthesizes backplane clocks at 2.048MHz, 4.096MHz, 8.192MHz, or 16.384MHz - all referenced to RCLK per CCR5 register settings.

Is the DS21Q48 pin-compatible with the DS2148?

No, the DS21Q48 is not pin-compatible with the DS2148. The DS2148 uses 44-pin TQFP or 49-ball CSBGA packages, while the DS21Q48 uses a 144-ball CSBGA (17mm × 17mm) package with entirely different pin assignment (Section 8, Figure 8-1). Although register maps and functional blocks are architecturally similar, PCB layout, thermal design, and interconnect routing are incompatible between the two families.