Renesas 728980J8

Overview

IDT728980J8 from Renesas Electronics (formerly IDT) is a 256 × 256 non-blocking time slot interchange (TSI) digital switch for ST-BUS®-compliant telecom systems. It supports eight 2.048 Mb/s serial input streams (RX0–RX7), eight 2.048 Mb/s serial output streams (TX0–TX7), microprocessor-controlled configuration via an 8-bit parallel bus, and operates from a single +5 V supply across –40°C to +85°C.

For engineers reviewing the IDT728980J8 datasheet, IDT728980J8 pinout, IDT728980J8 application, or IDT728980J8 equivalent, key selection considerations include ST-BUS® frame alignment (F0i), 4.096 MHz serial clock (C4i), per-channel connection memory control, ODE-driven output enable, and PLCC-44 packaging with three-state TX outputs.

Technical Context

The IDT728980J8 implements a dual-mode switching architecture: Connection Mode routes data from Data Memory using addresses stored in Connection Memory LOW, while Processor Mode directly outputs contents of Connection Memory LOW on TX streams. Internal serial-to-parallel and parallel-to-serial conversion enforces minimum 2-channel delay depending on RX/TX stream pairing (e.g., RX0→TX1 achieves minimal latency).

Control is managed through a 6-bit address bus (A0–A5), where A5 selects between Control Register (A5=0) and memory-mapped channel access (A5=1). The Control Register configures Split Memory mode, Processor Enable (PE), Stream Address (STA), and Memory Select bits-enabling precise per-stream, per-channel configuration of source, output enable, and CCO bit assignment.

Key Specifications

Pinout & Package

Package: 44-pin Plastic Leaded Chip Carrier (PLCC), J44 footprint, 0.65 in × 0.65 in, 0.05 in pitch, lead-free (Green) variant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar time slot interchange applications.

Compared with MC145506FN and Si2404-GM, the IDT728980J8 delivers native ST-BUS® timing (F0i/C4i), guaranteed 256×256 non-blocking performance at 5 V, and hardware-safe initialization via ODE - making it the only drop-in solution for retrofitting or maintaining legacy telecom infrastructure requiring zero-framing overhead.

Availability

IDT728980J8 is available at Aetrix Electronics and suitable for digital loop carrier systems, PCM multiplexers, telecom access nodes, and digital cross-connect systems requiring stable component supply across extended product lifecycles.

Supply support for IDT728980J8 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

Renesas Electronics Corporation is a global semiconductor leader formed from the merger of NEC Electronics, Renesas Technology, and IDT. It specializes in microcontrollers, analog, power, and connectivity solutions for automotive, industrial, and infrastructure markets.

The IDT728980J8 belongs to Renesas' legacy telecom TSI portfolio, designed specifically for ST-BUS®-based time-division multiplexing infrastructure - enabling reliable, low-latency channel switching in E1/T1 access equipment and digital switching systems.

FAQ

What is the function of the ODE pin on the IDT728980J8?

The ODE (Output Drive Enable) pin is a global active-HIGH control input that forces all TX0–TX7 serial outputs into high-impedance state when driven LOW - regardless of software configuration in Connection Memory HIGH. This provides hardware-level safety during power-up or fault conditions. When ODE is HIGH, individual TX channel drivers are enabled or disabled based on the OE bit in each Connection Memory HIGH location. The IDT728980J8 relies on this dual-layer control (ODE + per-channel OE) to prevent bus contention in multi-device switching matrices.

How does the IDT728980J8 achieve ST-BUS® compliance?

The IDT728980J8 achieves ST-BUS® compliance through dedicated hardware interfaces: F0i accepts an 8 kHz frame pulse to synchronize 125 µs frames, and C4i accepts a 4.096 MHz clock to sample 8-bit time slots at 2.048 Mb/s. Its internal serial-to-parallel converters align incoming RX data to frame boundaries, and its parallel-to-serial converters reconstruct ST-BUS®-formatted TX streams with precise bit ordering. All timing parameters (tFPS, tFPH, tCLK) meet ETSI-defined ST-BUS® specifications - confirmed in the AC Electrical Characteristics tables of the IDT728980J8 datasheet.

What are the two operational modes of the IDT728980J8, and how do they differ?

The IDT728980J8 supports Connection Mode and Processor Mode. In Connection Mode, the contents of Connection Memory LOW act as addresses pointing to Data Memory locations - enabling time slot routing from any RX channel to any TX channel. In Processor Mode, the contents of Connection Memory LOW are output directly on TX streams - allowing the microprocessor to inject custom data per time slot. Mode selection is controlled by the PE bit in the Control Register and per-channel CS bits in Connection Memory HIGH. The IDT728980J8 uses these modes to support both circuit-switched telephony and packetized voice gateway applications.

Can the IDT728980J8 be used in systems requiring less than 256 × 256 switching capacity?

Yes, the IDT728980J8 can be deployed in smaller-scale systems. Its 256 × 256 matrix is fully configurable - unused RX/TX streams can be left unconnected, and unused time slots can be set to high-impedance via OE bits. For example, a 64 × 64 application may use only RX0–RX1 and TX0–TX1, programming Connection Memory to route only those 64 channels while disabling others. The IDT728980J8 retains full functionality (F0i/C4i timing, ODE control, CCO output) regardless of utilization level - making it suitable for scalable designs from access nodes to central office switches.

What is the purpose of the CCO pin on the IDT728980J8?

The CCO (Control Channel Output) pin delivers a 2.048 Mb/s serial bitstream containing 256 bits per frame - one bit per time slot - sourced from the CCO bits in Connection Memory HIGH. Each CCO bit is transmitted one time slot before its associated TX channel (e.g., CCO bit for TX0, CH0 appears synchronously with TX7, CH31), enabling external logic to monitor or control per-slot behavior in real time. This feature supports diagnostic functions like channel activity logging, alarm insertion, or encryption key synchronization - unique to the IDT728980J8 among legacy TSI devices and critical for maintaining service-level agreements in carrier networks.