Renesas 72V8985JG8

Overview

IDT72V8985JG8 from Integrated Device Technology is a 3.3 V ST-BUS®/GCI-compatible digital time slot interchange (TSI) switch with 256 × 256 non-blocking channel capacity, 8 RX and 8 TX serial streams at 2.048 Mb/s, microprocessor-controlled 8-bit parallel interface, and per-channel variable or constant throughput delay modes. It serves as the core TSI matrix in voice/data multiplexing systems such as ISDN access nodes and digital loop carriers.

For engineers reviewing the IDT72V8985JG8 datasheet, IDT72V8985JG8 pinout, IDT72V8985JG8 application, or IDT72V8985JG8 equivalent, key selection criteria include frame integrity support for GCI/ST-BUS®, 3.3 V I/O with 5 V tolerant inputs, 44-pin PLCC package compatibility, -40°C to +85°C industrial temperature range, and microprocessor-accessible connection memory for dynamic path configuration.

Technical Context

The IDT72V8985JG8 implements a dual-mode TSI architecture: Variable Delay Mode (minimum 3 time slots, optimized for voice) and Constant Delay Mode (32–94 time slots, preserving frame integrity for data). Its internal timing unit auto-detects ST-BUS® (active-low frame sync) or GCI (active-high frame sync) formats via F0i and synchronizes to the 4.096 MHz C4i clock.

It features split-memory addressing (Control Register, Connection Memory HIGH/LOW, Data Memory), with A5–A0 enabling register selection and stream/channel targeting. The ODE pin provides master three-state control over TX0–TX7 outputs, while DTA delivers open-drain data acknowledgment with ≤800 ns max delay for connection memory accesses.

Key Specifications

Pinout & Package

Package: 44-pin PLCC (J44-1, order code J), 0.05 in pitch, 0.65 in × 0.65 in footprint. 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 IDT72V8985JG8, IDT72V8984JG8 offers identical functionality at half the switching density, while MC145506FN requires external level translation and manual format setup-making IDT72V8985JG8 the sole choice for new 3.3 V, auto-sensing, full-matrix TSI designs.

Availability

IDT72V8985JG8 is available at Aetrix Electronics and suitable for ISDN access nodes, digital loop carrier systems, and VoIP gateway media processing requiring stable component supply, long-term lifecycle assurance, and industrial temperature compliance.

Supply support for IDT72V8985JG8 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 (IDT) was a fabless semiconductor company specializing in timing, memory interface, RF, and interconnect solutions before its acquisition by Renesas Electronics in 2019. IDT pioneered high-performance TSI and clock management ICs for telecom infrastructure.

IDT72V8985JG8 belongs to IDT's legacy 3.3 V TSI switch family designed specifically for carrier-grade digital telephony systems requiring ST-BUS®/GCI compatibility, deterministic delay, and microprocessor configurability.

FAQ

What is the primary function of the IDT72V8985JG8 in a TDM system?

The IDT72V8985JG8 serves as a 256 × 256 non-blocking time slot interchange switch that dynamically routes individual 64 Kbit/s PCM time slots between eight 2.048 Mb/s serial input and output streams. Its role is to perform real-time, per-channel time slot reordering under microprocessor control-enabling call setup, conferencing, and channel grooming in digital telephony infrastructure. The IDT72V8985JG8 supports both Variable and Constant Delay modes to meet distinct voice and data timing requirements.

Does the IDT72V8985JG8 require external level shifters when interfaced with a 5 V microcontroller?

No, the IDT72V8985JG8 features 5 V tolerant digital inputs (CS, DS, R/W, A0–A5, F0i, C4i, ODE, RESET), allowing direct connection to 5 V microcontrollers without external level shifters. Its 3.3 V I/O outputs (D0–D7, DTA, CCO, TX0–TX7) are compatible with 3.3 V logic families, but the 5 V tolerance applies only to inputs-not outputs. Therefore, output signals driving 5 V receivers require external buffering or resistive termination if voltage translation is needed.

How does the IDT72V8985JG8 handle ST-BUS® versus GCI frame synchronization automatically?

The IDT72V8985JG8 uses its F0i input to detect frame sync polarity and format: it recognizes ST-BUS® by an active-low 8 kHz pulse and GCI by an active-high pulse. Based on this detection, the internal timing unit configures sampling edges-rising-edge sampling at 3/4 bit cell for ST-BUS®, falling-edge sampling for GCI-and aligns the 4.096 MHz C4i clock accordingly. This auto-detection occurs at power-up or reset and requires no software initialization or external configuration.

What is the minimum and maximum throughput delay achievable with the IDT72V8985JG8?

In Variable Delay Mode, the IDT72V8985JG8 achieves a minimum throughput delay of 3 time slots (e.g., input channel 0 → output channel 3) and a maximum of 34 time slots (e.g., input channel 30 → output channel 1). In Constant Delay Mode, delay ranges from 32 time slots (input channel 31 → output channel 0) to 94 time slots (input channel 0 → output channel 31), calculated as DELAY = [32 + (32 − IN) + (OUT − 1)]. These values are guaranteed and independent of traffic load.

Is the RESET pin available on the IDT72V8985JG8 PLCC package?

No, the RESET pin is not present on the IDT72V8985JG8 PLCC (J44-1) package. According to the datasheet, RESET is only provided on the SSOP package variant (SO48-1, order code PV). For the IDT72V8985JG8, system-level reset must be managed externally via the ODE pin (to place TX outputs in high-impedance) and software-initiated register clearing, since hardware reset is unavailable in this package configuration.