Renesas 728980JG

Overview

IDT728980JG from Renesas Electronics (formerly IDT) is a 256 × 256 non-blocking time slot interchange (TSI) digital switch for ST-BUS®-compliant telecom systems. It features 8 serial RX inputs and 8 TX outputs, each carrying 32 × 64 Kbit/s channels at 2.048 Mb/s frame rate, with microprocessor-controlled connection memory mapping and 5 V single-supply operation.

For engineers reviewing the IDT728980JG datasheet, IDT728980JG pinout, IDT728980JG application, or IDT728980JG equivalent, key selection criteria include ST-BUS® timing compliance (F0i frame sync, C4i 4.096 MHz clock), per-channel switching control via Connection Memory HIGH/LOW, ODE-driven three-state TX output management, and PLCC-44 packaging for legacy telecom board integration.

Technical Context

The IDT728980JG implements a dual-mode TSI architecture: Connection Mode routes Data Memory contents to TX streams using Connection Memory LOW as channel address pointers, while Processor Mode directly outputs Connection Memory LOW contents-enabling flexible time-slot assignment in PCM-based voice/data multiplexing. Internal serial-to-parallel and parallel-to-serial conversion enforces minimum 2-channel delay depending on RX/TX stream pairing.

Control is executed via an 8-bit microprocessor bus (D0–D7, A0–A5, CS, DS, R/W) with split-memory addressing (SM bit), processor-enable (PE bit), and per-channel configuration bits (CS, OE, CCO) stored in Connection Memory HIGH. The ODE pin provides global three-state control over all TX0–TX7 outputs independent of software state.

Key Specifications

Pinout & Package

Package: 44-pin PLCC (J44), 0.05″ pitch, green RoHS-compliant body per ordering code "JG".

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT728980JG, MC145506P offers reduced channel density and simplified control but lacks CCO and dual-mode capability, while MT8980AP adds MVIP support and PLL integration at the cost of larger package and increased design complexity-making IDT728980JG optimal for dedicated ST-BUS® systems needing precise per-channel control in compact PLCC form factor.

Availability

IDT728980JG is available at Aetrix Electronics and suitable for PCM voice multiplexers, digital loop carrier systems, ISDN PRI interface cards, and telecom test equipment requiring stable component supply and long-term lifecycle support.

Supply support for IDT728980JG 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 and Renesas Technology, specializing in microcontrollers, analog, power, and telecom ICs.

The IDT728980JG belongs to Renesas' legacy telecom timing and switching portfolio, designed specifically for ST-BUS®-based time-division multiplexing infrastructure in carrier-grade and enterprise voice systems.

FAQ

What is the primary function of the IDT728980JG in a telecom system?

The IDT728980JG serves as a 256 × 256 time slot interchange digital switch that dynamically routes individual 64 Kbit/s time slots between eight 2.048 Mb/s ST-BUS® input and output streams. Its core function is non-blocking TDM switching for voice/data grooming in E1-based infrastructure, enabling real-time channel reassignment under microprocessor control via Connection Memory HIGH/LOW registers. This makes IDT728980JG essential for PCM multiplexers, DLC systems, and ISDN interface cards where deterministic time-slot mapping is required.

How does the IDT728980JG handle timing synchronization with external networks?

The IDT728980JG synchronizes to external telecom networks using two dedicated inputs: F0i accepts an 8 kHz frame pulse aligned to E1 superframe boundaries, while C4i receives a 4.096 MHz bit clock derived from the same network source. These signals drive internal counters and serial shift registers to maintain strict ST-BUS® timing compliance-including 125 μs frame width, 32-slot structure, and bit-level alignment. The IDT728980JG does not generate clocks; it relies entirely on externally supplied, network-derived timing references to ensure zero-jitter switching in synchronous digital hierarchies.

What is the role of the ODE pin on the IDT728980JG, and how does it interact with software control?

The ODE (Output Drive Enable) pin on the IDT728980JG acts as a hardware-level master enable for all eight TX0–TX7 serial outputs. When ODE is driven LOW, all TX outputs enter high-impedance state regardless of Connection Memory HIGH (CMH) bit 0 settings-providing fail-safe bus isolation during power-up or fault conditions. When ODE is HIGH, per-channel output enable is governed by CMH bit 0, allowing selective activation/inactivation of individual time slots. This dual-layer control ensures robust initialization (ODE held low until CMH is programmed) and fine-grained runtime switching without risk of bus contention in matrix configurations.

Can the IDT728980JG operate in both Connection Mode and Processor Mode simultaneously?

No-the IDT728980JG operates in either Connection Mode or Processor Mode globally, controlled by the PE (Processor Enable) bit in the Control Register. When PE = 1, all TX channels output the contents of Connection Memory LOW (CML) every frame, effectively disabling hardware-based routing. When PE = 0, each channel's behavior is determined individually by bit 2 (CS) in its corresponding Connection Memory HIGH (CMH) location: CS = 1 selects Processor Mode for that channel; CS = 0 selects Connection Mode. Thus, mixed-mode operation is possible at the per-channel level only when PE = 0, enabling hybrid configurations such as some channels passing through CML data while others route from Data Memory.

What is the minimum propagation delay through the IDT728980JG, and what factors affect it?

The minimum propagation delay through the IDT728980JG is two time slots (i.e., two 64 Kbit/s channel periods), occurring only for specific RX-to-TX stream combinations listed in Table 1 of the datasheet-such as RX0 → TX1 or RX4 → TX4. This delay arises from mandatory serial-to-parallel conversion on input, storage in 256-position Data Memory, and parallel-to-serial conversion on output. Delay increases with inter-stream distance (e.g., RX0 → TX7 incurs greater latency than RX0 → TX1) and depends on whether data originates from Data Memory (Connection Mode) or Connection Memory LOW (Processor Mode). The IDT728980JG does not support zero-delay pass-through; all switching introduces at least one full frame offset for timing safety.