MB85RS256A - 256Kbit SPI FRAM Memory, 25 MHz | RAMXEED
部品番号: MB85RS256A ✓ 生産中| 数量 | 単価 | 小計 |
|---|---|---|
| 1 | $3.85 | $3.85 |
| 10 | $3.42 | $34.20 |
| 100 | $2.95 | $295.00 |
| 500 | $2.58 | $1,290.00 |
| 1,000 | $2.21 | $2,210.00 |
MB85RS256A 概要
An FRAM (Ferroelectric Random Access Memory) is a type of nonvolatile RAM that combines the fast write speed and unlimited endurance of SRAM with the data-retention behaviour of flash or EEPROM. FRAM cells store data as the polarisation state of a ferroelectric capacitor, so writes occur at bus speed (no erase/program delay) and the technology slots into the same hierarchy as SRAM -> nonvolatile memory -> memory IC -> semiconductor. This makes FRAM useful wherever systems must log data continuously without wearing out the storage medium.
Key features include an operating voltage range of 2.7 V to 3.6 V (extended 2.0 V to 3.6 V for lower-speed operation), 4.5 mA active read current at 25 MHz, 2.6 uA standby current, page-mode write capability up to 32 bytes, and hardware-controlled write protection via the /WP pin. The device also supports SPI Mode 0 (CPOL=0, CPHA=0) and Mode 3 (CPHA=1), making it compatible with most microcontroller SPI peripherals. Data retention is specified at 10 years.
The MB85RS256A uses a standard SPI instruction set with eight instructions (WREN, WRDI, READ, WRITE, RDSR, WRSR, FSTRD, SLEEP) and a built-in 8-byte SRAM write buffer that enables byte-aligned writes at full bus speed. Compared with EEPROM, the absence of a write cycle time means that wear-levelling firmware is unnecessary. Compared with serial flash, the device does not require an erase-before-write sequence, simplifying firmware and shortening worst-case commit latency.
Typical applications include data logging for smart meters and industrial sensors, black-box event recorders, PLC/industrial automation parameter storage, medical devices requiring frequent log writes, and gaming-console cartridge save storage (the part is widely used in the Game Boy / non-volatile cart community). The wide voltage range and low standby current also suit battery-backed IoT endpoints.
When designing with this part, note that the /WP pin must be tied high (inactive) for normal SPI operation, and decoupling of at least 0.1 uF should be placed within 5 mm of the VDD pin. Unlike EEPROM, FRAM has no internal charge pump and no page-write time, so write throughput equals read throughput when the buffer is kept full.
This page synthesises distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone, helping engineers compare the MB85RS256A against newer MB85RS256B revisions and cross-brand SPI FRAM from TI, Cypress, and ROHM.
ドロップイン代替品: MB85RS256A — 同一パッケージでピン互換。PCBの作り直しが必要な異なるパッケージの部品は除外されています。
クイック比較ツール — 並列比較する代替部品を選択:
MB85RS256B
✅ ドロップイン📋 参考代替品（カタログ未掲載）
MB85RS256APNF-G-JNE1
✅ ドロップイン📋 参考代替品（カタログ未掲載）
FM25V01
✅ ドロップイン📋 参考代替品（カタログ未掲載）
FM25W256
✅ ドロップイン📋 参考代替品（カタログ未掲載）
MR45V256A
✅ ドロップイン📋 参考代替品（カタログ未掲載）
MB85RS256A 最大定格＆電気的特性
| メモリタイプ | Nonvolatile FRAM (Ferroelectric RAM) |
| Memory Density | 256 Kbit (32,768 × 8 bit) |
| インターフェース | SPI (Mode 0 / Mode 3), up to 25 MHz |
| Operating Voltage | 2.7 V to 3.6 V (2.0 V to 3.6 V at lower speed) |
| Active Read Current | 4.5 mA typical at 25 MHz |
| Standby Current | 2.6 uA typical |
| Write Endurance | 10^10 read/write cycles per cell |
| Data Retention | 10 years |
| Write Cycle Time | None (writes at bus speed) |
| Page Write Buffer | Up to 32 bytes |
| 動作温度 | -40 C to +85 C |
| パッケージ | 8-pin SOP (150 mil) |
| 実装タイプ | Surface Mount |
| RoHS ステータス | Compliant |
| Write Protection | /WP pin (active low) |
MB85RS256A ピン構成
| ピン 1 | CS/ — Chip Select (active low) |
| ピン 2 | SO — Serial Output (MISO) |
| ピン 3 | /WP — Write Protect (active low) |
| ピン 4 | GND — Ground |
| ピン 5 | SI — Serial Input (MOSI) |
| ピン 6 | SCK — Serial Clock |
| ピン 7 | /HOLD — Hold (active low) |
| ピン 8 | VDD — Power supply (2.7 V to 3.6 V) |
主な用途
MB85RS256A の用途: 6 件s: Smart Meter Data Logging, PLC / Industrial Automation Parameter Storage, Medical Device Event / Patient Data Logging, IoT Sensor Endpoint Configuration Storage, Black-Box / Event Recorder Nonvolatile Log, Retro Gaming Console Cartridge Save Storage.
Smart Meter Data Logging
The MB85RS256A's 10^10 write endurance and bus-speed writes make it ideal for smart-meter data logging where the device records consumption telemetry every few seconds for 10+ years. With 256 Kbit (32 KB) it can buffer several days of interval data before flush, and the 2.7 V to 3.6 V range aligns with metering battery-backed rails. Unlike EEPROM, it requires no page-write firmware loops or wear levelling, reducing MCU code size and BOM cost in residential and industrial AMI deployments.
おすすめ
PLC / Industrial Automation Parameter Storage
Factory PLCs and industrial controllers frequently overwrite calibration setpoints, recipe parameters, and event counters in nonvolatile memory during normal operation. The MB85RS256A's 10^10 endurance and instant-write FRAM cells absorb this high-frequency update pattern without the wear that would destroy EEPROM or flash in months. SPI at 25 MHz and the 8-SOP footprint integrate with most 3.3 V industrial MCU SPI peripherals, and the -40 C to +85 C industrial temperature grade suits cabinet-mounted equipment on production lines.
おすすめ
Medical Device Event / Patient Data Logging
Medical monitors and diagnostic equipment require nonvolatile storage that survives frequent parameter updates (vital signs, event timestamps, calibration data) for the device lifetime. The MB85RS256A provides 256 Kbit FRAM with 10^10 cycle endurance and 10-year data retention, well beyond typical IEC 60601-1 design lifetimes. Its 4.5 mA active current and 2.6 uA standby help battery-powered infusion pumps and ambulatory monitors minimise drain, while the 8-SOP-150 footprint supports compact PCB assemblies used in patient-worn devices.
おすすめ
IoT Sensor Endpoint Configuration Storage
Battery-powered IoT sensor nodes (wireless environmental sensors, asset trackers, smart locks) frequently overwrite configuration parameters, authentication tokens, and rolling counters. The MB85RS256A's 2.6 uA standby current and 2.7 V to 3.6 V operating range suit coin-cell or Li-ION powered endpoints, while its 256 Kbit capacity holds months of buffered telemetry samples. SPI Mode 0/3 compatibility means it interfaces directly with common low-power MCUs (NRF52, STM32, ESP32) without glue logic, and the absence of an internal charge pump removes the EMI associated with EEPROM writes.
おすすめ
Black-Box / Event Recorder Nonvolatile Log
Automotive black-box recorders, industrial fault loggers, and elevator event recorders must capture high-speed event streams that arrive in milliseconds and survive without data loss across power cycles. The MB85RS256A writes at SPI bus speed (no erase delay), enabling event bursts up to 25 MHz with deterministic latency - critical for crash logs and machine-fault forensics. The 10-year data retention supports decade-long archives, and the 8-SOP-150 package fits inside the compact form factor typical of recorder modules.
おすすめ
Retro Gaming Console Cartridge Save Storage
The MB85RS256A is widely adopted by the retro gaming community as save storage in modified Game Boy, Analogue Pocket, and FPGA-based cartridge clones. Its 32 KB capacity comfortably holds save RAM for classic titles, and the bus-speed writes avoid the perceptible save-delay that EEPROM-based carts exhibit. The 8-SOP-150 package is straightforward to wire to cartridge-edge connectors, and the 10^10 endurance tolerates the millions of save operations accumulated by users over a console's lifetime.
おすすめ
おすすめ製品の概要
エンジニアリング参考データ: MB85RS256A — 比較、設計ガイダンス、コンプライアンス情報。
選定ガイド
代替品との比較
| パラメータ | この製品 | MB85RS256B | MB85RS256APNF-G-JNE1 | FM25V01 | FM25W256 | MR45V256A |
|---|---|---|---|---|---|---|
| Brand | RAMXEED (formerly Fujitsu Semiconductor) | RAMXEED | RAMXEED | Infineon (Cypress) | Infineon (Cypress) | ROHM Semiconductor |
| Package | 8-SOP (150 mil) | 8-SOP (150 mil) - same | 8-SOP (150 mil) - same | 8-SOP (150 mil) - same | 8-SOP (150 mil) - same | 8-SOP (150 mil) - same |
| Memory Density | 256 Kbit (32,768 x 8) | 256 Kbit | 256 Kbit | 256 Kbit | 256 Kbit | 256 Kbit |
| Interface / Max Clock | SPI 25 MHz | SPI 40 MHz | SPI 25 MHz | SPI 40 MHz | SPI 40 MHz | SPI 40 MHz |
| Operating Voltage | 2.7 V to 3.6 V | 2.7 V to 3.6 V | 2.7 V to 3.6 V | 2.0 V to 3.6 V | 2.0 V to 3.6 V | 2.0 V to 3.6 V |
| Write Endurance | 10^10 cycles | 10^10 cycles | 10^10 cycles | 10^14 cycles | 10^14 cycles | 10^10 cycles |
| Automotive Grade (AEC-Q100) | No (industrial -40 to +85 C) | No | No | No | Yes | No |
主な差別化要因
- Same RAMXEED family as successor MB85RS256B （vs MB85RS256B)
- Infineon FM25V01 cross-brand equivalent （vs FM25V01)
- Automotive AEC-Q100 variant available （vs FM25W256)
設計ノート
Decouple VDD (pin 8) with a 0.1 uF X7R ceramic placed within 5 mm of the package and a 10 uF bulk capacitor at the regulator output. The MB85RS256A draws 4.5 mA active at 25 MHz - estimated peak transient in the PSRP burst: roughly 6 mA in worst case. Tie /WP and /HOLD to VDD via 10 kΩ pull-ups when unused to prevent accidental write-protect or hold assertions from noise on floating traces.
Route SPI traces (SCK, SI, SO, CS/) as 50 Ω controlled-impedance microstrip and keep trace lengths under 50 mm to avoid ringing at 25 MHz. Place a 22-33 Ω series resistor on SCK close to the master to damp reflections. The MB85RS256A supports both SPI Mode 0 and Mode 3 - confirm the MCU's CPOL/CPHA match before initialising the peripheral, and always send WREN (0x06) before each WRITE (0x02) command.
Common pitfalls with the MB85RS256A: (1) forgetting WREN before WRITE causes silent dropped writes - poll the WEL bit in RDSR; (2) exceeding 32-byte page boundaries causes the write to wrap within the page - the device does NOT auto-increment; (3) operation below 2.7 V requires derating the SPI clock to 10 MHz or less; (4) leaving /WP or /HOLD floating during power-up can trigger unintended write-protect or hold states; (5) soldering profile must stay below 260 C peak for lead-free assembly to avoid damaging the ferroelectric cells.
コンプライアンス情報
RoHS and lead-free confirmed by RAMXEED product page (MB85RS256APNF-G-JNE1 variant). Not AEC-Q100 qualified - choose FM25W256 for automotive.
