Nec B58944 Datasheet Jun 2026
| Parameter | Specification | | :--- | :--- | | | 32,768 words × 8 bits | | Total Capacity | 262,144 bits (256 Kib) | | Access Time (Max) | 70 ns (for the -70L version) | | Supply Voltage (VCC) | 4.5 V to 5.5 V for standard operation | | Standby Current | 50 μA (max) for LL version, 3 μA (max) for L version | | Data Retention VCC | 2.0 V (min) | | Operating Ambient Temp | 0°C to 70°C (for the standard -70L version) | | Package | 28-pin Plastic SOP (450 mil / 11.43 mm wide) |
Based on the collected data, the B58944 is most likely a , manufactured by NEC (now Renesas). This likely means its internal functionality is that of a standard 32K x 8-bit (256 Kbit) CMOS static RAM with an access time of 70 nanoseconds. However, this is our strongest hypothesis and not a confirmed fact.
Examine the SOP-28 package pins using a microscope to look for solder fatigue or thermal discoloration.
: 70 nanoseconds (ns) maximum time window from address stabilization to valid data output (derived from the -70L / -70Y nomenclature). Supply Voltage ( VCCcap V sub cap C cap C end-sub ) : Normally operates on a regulated power plane. nec b58944 datasheet
Thermal expansion causes internal chip micro-cracks to expand, breaking connection lines when warm.
The fuel pump relay or ignition coils fail to receive pulse-width modulation (PWM) commands. In-Circuit Bench Testing
The NEC B58944 is engineered using a high-reliability CMOS process. It acts as high-speed volatile scratchpad memory for automotive microcontrollers, storing real-time sensor data, fault codes (DTCs), fuel trim maps, and operational variables. | Parameter | Specification | | :--- |
Common in EDC7 and EDC16 units for heavy vehicles like Iveco.
: Often paired or co-indexed with the D43256 family, indicating integrated Static RAM (SRAM) or logic interface structures designed for high-speed buffering and low latency.
You can find replacements on AliExpress and eBay for relatively low costs. Examine the SOP-28 package pins using a microscope
As an SRAM chip, the pinout follows the standard JEDEC layout for 32K x 8 memories: A0 – A14: Address Inputs. I/O1 – I/O8: Data Inputs/Outputs. modified CS with bar above modified CE with bar above Chip Select/Enable. modified WE with bar above Write Enable. modified OE with bar above Output Enable. Vcc / GND: Power Supply (5V) and Ground. 4. Applications and Use Cases Automotive ECUs: Its most frequent application is in Bosch automotive engine computers
Below is a technical summary of the component, which can serve as a reference paper for its datasheet. 1. Component Identification Manufacturer: NEC Electronics (now part of Renesas Electronics). Part Number: Functional Equivalent: $\mu$PD43256BGU-70L Common Branding: