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Home > Products > Integrated Circuits (ICs) > Logic > Signal Switches, Multiplexers, Decoders

Renesas IDT728985J

Name: IDT728985J
Brand: Renesas
SKU: IDT728985J
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: IDT728985J

Manufacturer:: Renesas

Category:: Signal Switches, Multiplexers, Decoders

Package:: 44-LCC (J-Lead)

Datasheet:: IDT728985J.pdf

Description:: IC MULTIPLEXER 1 X 8:8 44PLCC

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Product details

Overview

IDT728985J from Integrated Device Technology is a 256 × 256 non-blocking time slot interchange (TSI) digital switch IC for ST-BUS®/GCI-compliant telecom systems. It supports eight 2.048 Mb/s RX inputs and eight TX outputs, each carrying 32 × 64 Kbit/s PCM channels, with per-channel variable or constant throughput delay modes and microprocessor-controlled channel mapping via an 8-bit parallel bus.

For engineers reviewing the IDT728985J datasheet, IDT728985J pinout, IDT728985J application, or IDT728985J equivalent, this device serves as a core TSI element in digital PBX, voice-over-PCM multiplexers, ISDN trunk interfaces, and integrated data/multimedia network switching nodes requiring frame integrity, low-latency voice routing, or deterministic delay control.

Technical Context

The IDT728985J implements dual-mode time slot switching-Variable Delay mode (minimum 3-slot latency, ideal for voice) and Constant Delay mode (32–94-slot fixed latency, preserving frame alignment for data). Its internal architecture includes serial-to-parallel converters for eight RX streams, 256-position Data Memory, split Connection Memory (HIGH/LOW), and a timing unit synchronized to 4.096 MHz C4i clock and 8 kHz F0i frame pulse.

It features automatic ST-BUS®/GCI format detection via F0i polarity analysis, three-state TX outputs controlled by ODE and per-channel OE bits, and a non-multiplexed 8-bit microprocessor interface (A0–A5, D0–D7, CS, DS, R/W, DTA) supporting read/write access to Control Register, Connection Memory, and Data Memory (read-only).

Key Specifications

Parameter	Value and Actual Design Meaning
Switch Capacity	256 × 256 non-blocking TDM channel matrix, enabling full crosspoint connectivity between 8 input and 8 output serial streams.
Data Rate per Stream	2.048 Mb/s serial I/O (32 × 64 Kbit/s PCM channels per RX/TX line), compliant with E1/G.703 and ST-BUS®/GCI physical layer specs.
Throughput Delay Modes	Per-channel selectable: Variable Delay (3–34 slots, min latency for voice) or Constant Delay (32–94 slots, frame-aligned for data).
Microprocessor Interface	8-bit non-multiplexed bus with A0–A5 addressing, CS/DS/R/W control, and open-drain DTA acknowledgment (max 1220 ns for Data Memory reads).
Supply & Temp Range	+5.0 V ±5% supply (VCC = 4.75–5.25 V); industrial operating temperature range of –40°C to +85°C.
Package	44-pin Plastic Leaded Chip Carrier (PLCC, J44-1), 0.05″ pitch, 0.65″ × 0.65″ footprint - order code suffix 'J'.
Serial Clock Input	C4i = 4.096 MHz master clock, used for bit-level sampling and framing; supports both ST-BUS® (active-low frame sync) and GCI (active-high) formats.

Pinout & Package

Package: 44-pin PLCC (J44-1), 0.05″ pitch, 0.65″ × 0.65″ body size, surface-mount compatible with standard PLCC sockets or reflow soldering.

Pin	Circuit Role	Design Meaning
GND (Pins 10, 31)	Ground reference	Dual ground pins ensure stable return path for analog and digital sections; required for noise immunity in high-speed TDM switching.
VCC (Pin 22)	+5.0 V power supply	Single 5 V rail powers entire device; decoupling capacitor (0.1 µF) recommended adjacent to pin.
RX0–RX7 (Pins 2–9)	Serial data inputs	Eight 2.048 Mb/s PCM input streams; each carries 32 × 64 Kbit/s time slots; sampled on rising/falling edge of C4i depending on detected ST-BUS®/GCI mode.
TX0–TX7 (Pins 11–18)	Three-state serial outputs	Eight 2.048 Mb/s output streams; output state controlled globally by ODE and per-channel by CMH[0]; high-impedance when disabled.
F0i (Pin 21)	Frame synchronization input	8 kHz frame pulse input; automatically identifies polarity and format (ST-BUS® active-low / GCI active-high) to configure internal timing unit.
C4i (Pin 20)	Serial clock input	4.096 MHz master clock; defines bit cell boundaries and drives internal serial-to-parallel/parallel-to-serial conversion logic.
A0–A5 (Pins 23–28)	Address inputs	6-bit address bus selects Control Register (A5=0) or memory locations (A5=1, A0–A4 select channel 0–31 within stream).
D0–D7 (Pins 32–39)	Bidirectional data bus	8-bit parallel interface for CPU read/write to Control Register, Connection Memory LOW/HIGH, and Data Memory (read-only).
CS (Pin 12)	Chip select	Active-low enable for microprocessor access; must be asserted with DS to initiate internal read/write cycles.
DS (Pin 13)	Data strobe	Active-high signal that latches address and initiates bus transaction; works with CS and R/W to generate internal timing.
R/W (Pin 14)	Read/write control	High = read, Low = write; controls direction of D0–D7 during microprocessor interface transactions.
DTA (Pin 15)	Data acknowledge	Open-drain, active-low output signaling completion of bus transfer; requires external pull-up; max delay 1220 ns for Data Memory reads.
ODE (Pin 29)	Output drive enable	Global three-state control for all TX0–TX7 outputs; LOW forces all outputs to high-impedance regardless of CMH settings.
CCO (Pin 30)	Control channel output	2.048 Mb/s serial output carrying 256 bits/frame (1 bit per channel); bit value sourced from CMH[1] for corresponding channel.

Key Features

Feature	Design Value
Automatic ST-BUS®/GCI format detection	Eliminates manual configuration: F0i polarity analysis determines interface standard and configures internal timing edges without software intervention.
Per-channel delay mode selection	Each of 256 channels independently configured for Variable Delay (voice-optimized) or Constant Delay (data-integrity-critical) via CMH[6].
Split memory addressing architecture	Enables simultaneous CPU access to Connection Memory (LOW/HIGH) and Data Memory using A5 as mode selector and STA bits for stream targeting.
Processor Mode and Connection Mode operation	Processor Mode (PE bit set) routes CPU-written CML data directly to TX outputs; Connection Mode uses CML as pointer into Data Memory for switched PCM routing.
Guaranteed minimum throughput delay	3-slot minimum latency in Variable Delay mode ensures real-time voice interconnect; deterministic 32-slot base delay in Constant Delay mode preserves frame sequence.

Applications

ISDN Primary Rate Interface (PRI) Multiplexer	Digital PBX Time-Slot Switching
Use Scenario: Aggregating 30 B-channels and 1 D-channel from multiple E1 lines into a unified PRI backplane with dynamic time-slot reassignment. IC Role / Device Role / Timing Role: Core TSI fabric performing non-blocking 256×256 time-slot routing between RX and TX serial streams under microprocessor control. Use Value: Enables flexible call setup, conferencing, and trunk sharing while maintaining strict 8 kHz frame alignment and sub-frame jitter tolerance.	Use Scenario: Implementing scalable voice switching in carrier-grade digital PBX systems handling up to 256 concurrent voice calls across multiple shelves. IC Role / Device Role / Timing Role: Time-slot interchange engine providing per-call latency control and broadcast capability (one RX channel → multiple TX channels). Use Value: Supports low-latency voice paths (<1 ms) in Variable Delay mode and maintains data channel integrity for signaling protocols in Constant Delay mode.
PCM-Based Voice over IP Gateway	TDM Over Packet Network Edge Node
Use Scenario: Bridging legacy TDM voice infrastructure to VoIP networks by extracting, buffering, and repackaging individual 64 Kbit/s PCM channels. IC Role / Device Role / Timing Role: Precision time-slot demultiplexer and remultiplexer, synchronizing incoming E1 frames to packetized output timing. Use Value: Provides deterministic delay and frame boundary visibility essential for jitter buffer design and echo cancellation in gateway applications.	Use Scenario: Edge node converting TDM traffic to pseudowire (e.g., SAToP) for transport over MPLS or Ethernet, requiring strict TDM structure preservation. IC Role / Device Role / Timing Role: Frame-aligned TSI ensuring constant-delay switching to prevent payload misalignment and maintain CESoPSN compliance. Use Value: Guarantees 32-slot minimum delay and frame integrity across all switched channels, satisfying RFC 5086 and ITU-T Y.1413 requirements.

ISDN Primary Rate Interface (PRI) Multiplexer

Digital PBX Time-Slot Switching

Use Scenario: Aggregating 30 B-channels and 1 D-channel from multiple E1 lines into a unified PRI backplane with dynamic time-slot reassignment.

IC Role / Device Role / Timing Role: Core TSI fabric performing non-blocking 256×256 time-slot routing between RX and TX serial streams under microprocessor control.

Use Value: Enables flexible call setup, conferencing, and trunk sharing while maintaining strict 8 kHz frame alignment and sub-frame jitter tolerance.

Use Scenario: Implementing scalable voice switching in carrier-grade digital PBX systems handling up to 256 concurrent voice calls across multiple shelves.

IC Role / Device Role / Timing Role: Time-slot interchange engine providing per-call latency control and broadcast capability (one RX channel → multiple TX channels).

Use Value: Supports low-latency voice paths (<1 ms) in Variable Delay mode and maintains data channel integrity for signaling protocols in Constant Delay mode.

PCM-Based Voice over IP Gateway

TDM Over Packet Network Edge Node

Use Scenario: Bridging legacy TDM voice infrastructure to VoIP networks by extracting, buffering, and repackaging individual 64 Kbit/s PCM channels.

IC Role / Device Role / Timing Role: Precision time-slot demultiplexer and remultiplexer, synchronizing incoming E1 frames to packetized output timing.

Use Value: Provides deterministic delay and frame boundary visibility essential for jitter buffer design and echo cancellation in gateway applications.

Use Scenario: Edge node converting TDM traffic to pseudowire (e.g., SAToP) for transport over MPLS or Ethernet, requiring strict TDM structure preservation.

IC Role / Device Role / Timing Role: Frame-aligned TSI ensuring constant-delay switching to prevent payload misalignment and maintain CESoPSN compliance.

Use Value: Guarantees 32-slot minimum delay and frame integrity across all switched channels, satisfying RFC 5086 and ITU-T Y.1413 requirements.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
IDT728984J	256 × 128 capacity (half the output channels); identical PLCC-44 package, same 4.096 MHz clock, and ST-BUS®/GCI compatibility.	Suitable for cost-sensitive or lower-port-count systems where only 4 TX outputs are needed instead of 8.	Select IDT728984J when full 256×256 non-blocking matrix is unnecessary and board space or BOM cost optimization is prioritized.
Cypress CY22394	Programmable clock generator with integrated TSI function; supports 64 × 64 switching, 3.3 V operation, and I²C configuration - no native ST-BUS®/GCI auto-detect.	Targeted at mixed-signal SoC clocking + light TSI tasks, not standalone telecom switching; lacks per-channel constant/variable delay control.	Choose CY22394 only for embedded systems needing combined clock synthesis and basic time-slot routing, not carrier-grade TDM switching.

Compared with IDT728985J, IDT728984J offers reduced port count but identical interface and timing behavior, while CY22394 provides integrated clock generation at the expense of TSI scale, voltage compatibility, and telecom-specific features like automatic format detection and guaranteed frame-aligned delay.

Availability

IDT728985J is available at Aetrix Electronics and suitable for digital PBX infrastructure, ISDN PRI multiplexers, and TDM-over-packet edge nodes requiring stable component supply, long-term lifecycle support, and verified telecom-grade reliability.

Supply support for IDT728985J 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), now part of Renesas Electronics, is a fabless semiconductor company specializing in timing, memory interface, RF, and high-performance interconnect solutions for communications and computing markets.

The IDT728985J belongs to IDT's Time Slot Interchange (TSI) product line, designed specifically for carrier-class TDM switching in voice and integrated data networks requiring precise frame synchronization, low-latency routing, and ST-BUS®/GCI protocol compliance.

FAQ

What is the primary function of the IDT728985J in a telecom system?

The IDT728985J functions as a 256 × 256 non-blocking time slot interchange digital switch, enabling dynamic, microprocessor-controlled routing of individual 64 Kbit/s PCM channels between eight 2.048 Mb/s serial input and output streams. It is deployed in digital PBX, ISDN multiplexers, and TDM gateways to perform real-time voice/data channel switching while preserving frame integrity and meeting strict telecom timing requirements.

Does the IDT728985J support both ST-BUS® and GCI interface standards?

Yes, the IDT728985J natively supports both ST-BUS® and GCI standards through automatic frame synchronization polarity detection on the F0i input. It internally configures its timing unit to match the detected format-using active-low frame pulses for ST-BUS® and active-high for GCI-without requiring external mode selection or firmware configuration.

How does the IDT728985J achieve deterministic throughput delay in Constant Delay mode?

In Constant Delay mode, the IDT728985J uses a multi-buffer Data Memory architecture to guarantee that input data written during frame N is always read out during frame N+2. This enforces a fixed minimum delay of 32 time slots and ensures frame-aligned output regardless of source/destination channel pairing, which is critical for data applications requiring strict sequence integrity.

What is the role of the ODE pin on the IDT728985J?

The ODE (Output Drive Enable) pin on the IDT728985J acts as a global three-state control for all eight TX0–TX7 serial outputs. When ODE is driven LOW, all TX outputs enter high-impedance state irrespective of per-channel settings in Connection Memory HIGH. This allows safe power-up initialization and system-level output isolation.

Can the IDT728985J operate with a 3.3 V supply?

No, the IDT728985J is specified exclusively for +5.0 V ±5% operation (4.75–5.25 V). Its electrical characteristics-including VIH/VIL thresholds, output drive strength, and internal logic levels-are validated only at 5 V. Using 3.3 V will result in undefined behavior, failed timing margins, and potential functional failure.

IDT728985J Specifications

Product attributes: Attribute value

Manufacturer:: Renesas

Series:: 7200

Package/Case:: 44-LCC (J-Lead)

Packaging:: Tube

Product Status:: Obsolete

Type:: Multiplexer

Circuit:: 1 x 8:8

Independent Circuits:: 1

Current - Output High, Low:: -

Voltage Supply Source:: Single Supply

Voltage - Supply:: 4.75V ~ 5.25V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 44-PLCC (16.59x16.59)

IDT728985J FAQ

1.How can I place an order for IDT728985J through Aetrix?

Please submit a Request for Quotation (RFQ) for IDT728985J on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for IDT728985J reliable?

The price and inventory of IDT728985J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for IDT728985J is usually 5 days.

3.What payment methods are accepted for IDT728985J?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for IDT728985J transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for IDT728985J?

IDT728985J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your IDT728985J order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for IDT728985J?

For technical support, including IDT728985J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your IDT728985J requirements.

6.How does Aetrix verify that IDT728985J is sourced from the original manufacturer or authorized distributors?

All IDT728985J products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that IDT728985J meets industry standards.

7.What is the process for return or replacement of IDT728985J?

All IDT728985J units undergo pre-shipment inspection (PSI). If there is an issue with IDT728985J, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The IDT728985J part is unused and in its original packaging.

Return procedure for IDT728985J:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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