Renesas Electronics America Inc IDT71P74804S250BQ

Product Summary IDT71P74804S250BQ Renesas QDR II SRAM

The IDT71P74804S250BQ from Renesas Electronics Corporation is a high-density, high-speed synchronous static random access memory (SRAM) device featuring the QDR™ II architecture. With 18Mbit capacity, organized as either 1M x 18-bit or 512K x 36-bit, this memory IC is offered in a 165-ball fine-pitch BGA package, making it suitable for demanding communication, networking, and data processing systems. This device is engineered to simultaneously support independent read and write accesses at elevated frequencies up to 250 MHz, delivering an 8.4 ns access time and quad-data-rate performance for maximum data throughput.

Main Features and Design Advantages of the IDT71P74804S250BQ QDR II SRAM

The IDT71P74804S250BQ distinguishes itself through several critical architectural features tailored for high-performance applications:

Independent read and write ports allow for concurrent transactions, eliminating bus contention and simplifying system-level signal integrity.

DDR (Double Data Rate) data bus transmits four words per clock cycle, quadrupling throughput compared to standard single-data-rate SRAMs at comparable clock speeds.

Dual echo clock outputs closely align with data signals, enabling downstream systems to reliably capture output at high speed without requiring the design of alternate, precisely-timed clocks.

Multiplexed address bus supports one read or write request per clock cycle for streamlined addressing.

Output drive strength is programmable via an external impedance control, allowing on-the-fly adaptation to varying PCB trace characteristics and system requirements.

Full compliance with HSTL (High-Speed Transceiver Logic) inputs supports scalable voltage interfacing between 1.4V and 1.9V, and the 1.8V core enables integration into modern low-voltage designs.

These architectural choices enable the device to provide exceptional system bandwidth, reduce design complexity for signal integrity at gigabit speeds, and offer the flexibility necessary for advanced networking or telecommunications infrastructure.

Operational Functions of the IDT71P74804S250BQ QDR II SRAM

The QDR II architecture at the heart of the IDT71P74804S250BQ provides true simultaneous access via independent read and write ports, each supporting four-word burst transfers. The memory accesses are pipelined and managed with byte-write control signals, allowing granular control over data modification. Addressing is managed via a multiplexed address bus, enabling efficient read and write operation interleaving on alternate clock cycles. If both operations are requested simultaneously, the architecture prioritizes read accesses, ensuring predictability for timing-critical systems.

The device also supports depth expansion, with specific address bits reserved for compatibility with higher-density memory modules. Designers benefit from built-in data forwarding logic—if a read follows a write to the same address in immediate succession, the new value is returned, thus facilitating rapid transaction cycles required in networking or buffer management applications.

Timing and Clock Structure in the IDT71P74804S250BQ QDR II SRAM

Efficient clock management in high-performance synchronous memory is vital, and the IDT71P74804S250BQ provides multiple clock domains for enhanced flexibility. It accepts two sets of input clocks (K/K and C/C), while generating dual echo clocks (CQ/CQ) aligned with output data. The architecture leverages an internal delay-locked loop (DLL) for precise timing alignment between incoming clocks and data output, ensuring robust synchronous operation across temperature and voltage variations.

Single clock mode is supported by disabling C and C clocks, further simplifying timing design when required by the system. DLL operation may also be disabled for specific use-cases where direct clock-to-output alignment is preferred. Programmable impedance adjustments, synchronized every 1024 clock cycles, help maintain consistent high-speed operation even with environmental changes.

Electrical Specs and System Compatibility of the IDT71P74804S250BQ QDR II SRAM

The IDT71P74804S250BQ supports a commercial temperature range (0°C to 70°C) and provides flexibility in interface voltage (VDDQ from 1.4V to 1.9V, core voltage at 1.8V). Input capacitance, operating and standby currents, and output drive characteristics are optimized for gigabit-per-second signaling, consistent with its QDR II design goals. All drive strengths are programmable and supported by external RQ impedance adjustment, enabling system designers to match transmission line characteristics, reducing reflections and EMI.

A comprehensive set of DC and AC electrical specifications ensures that signal margins are maintained for both input and output circuitry. Built-in features such as automatic output enable/disable (high impedance output when not valid) and byte-wide write are supported for advanced system control.

Package Details and Pin Layout for the IDT71P74804S250BQ QDR II SRAM

The device is housed in a space-efficient 165-ball fine-pitch BGA package (13mm x 15mm, 1.0mm ball pitch), supporting both x18 and x36 configurations to facilitate board-level density optimization. Detailed pinouts and reserved address lines for future expansion are provided for straightforward PCB integration.

Notes on configuration detail support proper connectivity—certain address pins must be tied to ground (VSS) to prevent floating inputs in lower-density applications, and reserved pins accommodate scalability for larger memory systems.

JTAG Testing Capabilities in the IDT71P74804S250BQ QDR II SRAM

Integrated IEEE 1149.1 boundary scan (JTAG) support delivers robust in-system testability for manufacturing validation and board-level diagnostics. The TAP controller, identification/bypass registers, and defined instruction set facilitate chainable scan operations, pad connectivity verification, and ID signature read-out. All electrical characteristics for the JTAG port are consistent with system integration standards, optimizing for mixed-signal layouts and supporting standard scan chain architectures.

Alternative and Substitute Models for the IDT71P74804S250BQ QDR II SRAM

For system design flexibility or long-term supply assurance, engineers may examine related QDR II SRAM products such as the IDT71P74604S250BQ (512K x 36-bit variant, same total density), or QDR II SRAMs produced by partner companies including Cypress Semiconductor and Micron Technology, Inc. These products share the core architectural features and may offer variants in density, configuration, or speed grade. Careful review of the interface, package size, and feature set is recommended to ensure drop-in compatibility or to enable seamless upgrades in existing designs.

Conclusion

The Renesas IDT71P74804S250BQ QDR II 18Mbit SRAM stands out as a high-throughput, highly-integrated synchronous memory solution, designed for advanced communications and process-critical applications. Its architectural optimizations—from dual independent access ports and echo clocks to programmable output impedance and robust JTAG test features—ensure signal integrity, ease of integration, and exceptional performance. For product selection engineers and procurement teams, this device forms the backbone of systems requiring reliable, concurrent high-speed data exchange, and represents a sound investment for future-proofed designs.