Renesas 72V8985J8

Overview

IDT72V8985J8 from Integrated Device Technology, Inc. is a 3.3 V ST-BUS®/GCI-compatible digital time slot interchange (TSI) switch implementing a non-blocking 256 × 256 channel matrix for TDM voice and data networks. It supports eight 2.048 Mb/s RX inputs and eight TX outputs, each carrying 32 × 64 Kbit/s channels, with per-channel variable or constant throughput delay modes and microprocessor-controlled routing via an 8-bit parallel interface.

For engineers reviewing the IDT72V8985J8 datasheet, IDT72V8985J8 pinout, IDT72V8985J8 application, or IDT72V8985J8 equivalent, key selection criteria include frame integrity support in Constant Delay mode (32–94 time slot delay), automatic ST-BUS®/GCI format detection on F0i/C4i, 3.3 V I/O with 5 V tolerant inputs, PLCC-44 packaging, and ODE-controlled three-state serial outputs for bus sharing in multi-device TSI systems.

Technical Context

The IDT72V8985J8 implements dual operational modes-Connection Mode (hardware-routed time slot mapping via Connection Memory LOW) and Processor Mode (CPU-written data output)-with per-channel control over delay type (V/C bit), source selection (CS bit), output enable (OE bit), and CCO bit assignment. Its internal timing unit synchronizes to 4.096 MHz (C4i) and auto-detects frame polarity/format (ST-BUS® active-low vs. GCI active-high) from F0i.

It uses a 256-position Data Memory for input buffering and split Connection Memory (HIGH/LOW) for routing configuration. In Constant Delay mode, it guarantees frame-aligned switching across all paths using double-buffered memory (input frame N → output frame N+2), while Variable Delay mode achieves minimum 3-slot latency for low-jitter voice paths. The DTA signal provides programmable acknowledgment timing (up to 1220 ns for Data Memory reads).

Key Specifications

Pinout & Package

Package: 44-pin Plastic Leaded Chip Carrier (PLCC), 0.65 in × 0.65 in, 0.05 in pitch (order code J). Pin 1 index corner marked; pins 1–22 and 33–44 on top row, pins 23–32 on bottom row (top view).

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT72V8985J8, IDT72V8983J8 offers identical footprint and control but halves switching capacity and removes CCO, while MC145506FN demands board-level redesign due to multiplexed bus and lack of auto-detection-neither is pin-compatible nor functionally equivalent.

Availability

IDT72V8985J8 is available at Aetrix Electronics and suitable for ISDN PRA systems, E1 line concentrators, VoIP gateway media planes, and TDM-over-IP edge routers requiring stable component supply across extended product lifecycles.

Supply support for IDT72V8985J8 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

Integrated Device Technology, Inc. (IDT) is a fabless semiconductor company specializing in timing, memory interface, RF, and high-performance interconnect solutions for communications and computing infrastructure.

The IDT72V8985J8 belongs to IDT's time slot interchange (TSI) product line, designed specifically for carrier-grade TDM switching in E1/T1 access equipment, PBX systems, and VoIP gateways requiring deterministic latency and frame-aligned data routing.

FAQ

What is the primary function of the IDT72V8985J8 in a TDM system?

The IDT72V8985J8 serves as a 256 × 256 non-blocking time slot interchange switch that dynamically routes 64 Kbit/s PCM channels between eight serial input and eight output streams. It enables flexible circuit-switched connectivity in E1-based infrastructure, supporting both voice (via Variable Delay mode) and data (via Constant Delay mode) traffic with microprocessor-controlled path setup and monitoring.

Does the IDT72V8985J8 support both ST-BUS® and GCI interface standards?

Yes, the IDT72V8985J8 automatically detects and adapts to both ST-BUS® and GCI formats using the F0i frame pulse input. It identifies polarity (active-HIGH for GCI, active-LOW for ST-BUS®) and configures internal timing accordingly-no external configuration or mode pins are required for compatibility.

How does the ODE pin affect the TX outputs of the IDT72V8985J8?

The ODE (Output Drive Enable) pin is a master hardware control that forces all eight TX outputs into high-impedance state when driven LOW, overriding per-channel OE bits in Connection Memory HIGH. When ODE is HIGH, individual TX channels can be enabled or disabled via software control, enabling safe bus sharing in multi-device TSI configurations.

What is the minimum and maximum throughput delay achievable with the IDT72V8985J8?

In Variable Delay mode, the IDT72V8985J8 achieves a minimum delay of three time slots (ideal for low-latency voice), while Constant Delay mode guarantees frame-aligned switching with delays ranging from 32 to 94 time slots-calculated as DELAY = [32 + (32 − IN) + (OUT − 1)]-to preserve data integrity across concatenated TDM links.

Is the IDT72V8985J8 compatible with 5 V logic systems?

The IDT72V8985J8 operates from a 3.3 V supply but features 5 V tolerant digital inputs (VI up to 5.25 V), allowing direct interfacing with 5 V microprocessors and peripheral logic without level-shifting. Its outputs are 3.3 V LVTTL compliant, requiring external level translation only when driving 5 V loads.