Renesas 7140LA55CB

Overview

7140LA55CB from IDT (Integrated Device Technology) is a 1K × 8 dual-port static RAM configured as a slave device in MASTER/SLAVE memory expansion systems, supporting fully asynchronous left/right port access with 55 ns maximum read cycle time, 1 mA typical standby current, and 2 V data retention capability. It serves as the SLAVE unit paired with IDT7130 MASTER in 16-bit-or-wider memory subsystems for real-time interprocessor communication.

For engineers reviewing the 7140LA55CB datasheet, 7140LA55CB pinout, 7140LA55CB application, or 7140LA55CB equivalent, key selection considerations include its BUSY input behavior (not output), INT flag support for port-to-port signaling, battery backup operation at 2 V, industrial temperature range (–40°C to +85°C), and compatibility with 48-pin ceramic flatpack (FP48) packaging.

Technical Context

The 7140LA55CB operates as a SLAVE dual-port SRAM with dedicated BUSY inputs (BUSYL, BUSYR) that inhibit writes when asserted low-unlike the MASTER IDT7130 which drives BUSY outputs. Its arbitration logic responds only to address match detection and requires tAPS ≥ 5 ns setup to prevent indeterminate BUSY assertion.

It supports R/W-controlled and CE-controlled write cycles with tWP = 30 ns (min), tWC = 55 ns (min), and tDW = 20 ns (min); all I/O pins are TTL-compatible, and both ports share independent CE, OE, R/W, and address lines enabling true concurrent access without external logic.

Key Specifications

Pinout & Package

48-pin ceramic flatpack (FP48) package with 0.75″ × 0.75″ footprint and 0.11″ height; body material is alumina ceramic with side-brazed leads for hermetic sealing and thermal robustness.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-port SRAM applications.

Compared with CY7C135-55JC and AS7C31025B-55JC, the 7140LA55CB uniquely delivers SLAVE-specific BUSY input behavior, 2 V data retention, and FP48 hermetic packaging-making it irreplaceable in high-reliability MASTER/SLAVE memory expansion systems.

Availability

7140LA55CB is available at Aetrix Electronics and suitable for real-time interprocessor communication, redundant control system memory, digital signal processor co-processor buffering, and legacy industrial bus interface bridging requiring stable component supply across extended product lifecycles.

Supply support for 7140LA55CB 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

IDT (Integrated Device Technology) was a fabless semiconductor company specializing in high-performance memory, timing, and interface ICs before its acquisition by Renesas Electronics in 2019.

The IDT7140 family was engineered specifically for MASTER/SLAVE dual-port SRAM expansion in real-time embedded systems-enabling 16-bit+ word widths without discrete glue logic or timing penalties.

FAQ

What is the function of BUSYL and BUSYR on the 7140LA55CB?

BUSYL and BUSYR are dedicated input pins on the 7140LA55CB-unlike the MASTER IDT7130, which drives them as outputs. When either BUSYL or BUSYR is driven low by the MASTER device, the corresponding port's write operations are internally inhibited. This hardware handshake prevents memory corruption during simultaneous access to the same address location, and is fundamental to the 7140LA55CB's role as a SLAVE in MASTER/SLAVE configurations.

Does the 7140LA55CB support battery backup operation?

Yes, the 7140LA55CB supports battery backup operation with guaranteed data retention down to 2.0 V (VDR), as specified in Table 7 of the datasheet. In data retention mode, ICCDR is ≤4000 µA (military/industrial) or ≤1500 µA (commercial) at VCC = 2.0 V and TA = +25°C. This allows direct connection to a lithium coin cell without regulation, preserving memory contents during main power loss-a key requirement in railway signaling and medical device black-box logging.

What package type is used for the 7140LA55CB?

The 7140LA55CB is packaged in a 48-pin ceramic flatpack (FP48), as confirmed by Pin Configuration diagrams on pages 3 and 4 of the datasheet. The FP48 body measures approximately 0.75″ × 0.75″ × 0.11″ and features side-brazed leads for hermetic sealing-providing superior moisture resistance and thermal stability versus plastic DIP or PLCC alternatives, especially under industrial temperature cycling.

Can the 7140LA55CB operate as a standalone dual-port RAM?

No-the 7140LA55CB is explicitly designed as a SLAVE device and cannot function autonomously. It lacks on-chip port arbitration logic and relies on an external IDT7130 MASTER to drive BUSY signals and manage contention. Attempting standalone use results in undefined write behavior when both ports access the same address. The datasheet states: "IDT7140 (SLAVE): BUSY is input", confirming its dependency on MASTER coordination.

What is the minimum setup time required for arbitration priority (tAPS) on the 7140LA55CB?

The 7140LA55CB requires a minimum arbitration priority setup time (tAPS) of 5 ns, as specified in Table 11a and 11b of the datasheet. This parameter ensures deterministic BUSY assertion during address-match arbitration between MASTER and SLAVE. If tAPS < 5 ns, the BUSY response becomes indeterminate-potentially causing data corruption. Layout must minimize skew between address and enable signals to guarantee this timing across temperature and voltage corners.