Ramtron FM1808B-PG

Overview

FM1808B-PG from Cypress Semiconductor (formerly Ramtron) is a 256Kbit bytewide ferroelectric nonvolatile RAM organized as 32,768 × 8 bits, operating at 5V with 70 ns access time and 130 ns cycle time. It delivers NoDelay™ writes, 10¹² read/write endurance, and 38-year data retention at +75°C - replacing battery-backed SRAM in industrial logging, metering, and real-time control systems where rapid, reliable nonvolatile writes are critical.

For engineers reviewing the FM1808B-PG datasheet, FM1808B-PG pinout, FM1808B-PG application, or FM1808B-PG equivalent, key selection considerations include its JEDEC-standard 32K×8 SRAM/EEPROM-compatible parallel interface, /CE-latched address timing, monolithic RoHS-compliant PDIP-28 package, and absence of write polling or battery management overhead.

Technical Context

The FM1808B-PG implements a ferroelectric memory array with row-based endurance architecture: each 8-byte boundary defines a 64-bit row, and every read/write accesses an entire row. Address latching occurs on the falling edge of /CE, initiating both memory access and mandatory precharge - unlike SRAM, /CE must strobe per cycle and cannot be permanently grounded.

Its functional truth table distinguishes three states: /CE high enables standby/precharge; /CE low + /WE high enables read (with /OE-controlled output); /CE low + /WE low enables write (no delay, no polling). Output drivers are tri-stated when /OE is high or during precharge, minimizing bus contention and supply transients.

Key Specifications

Pinout & Package

FM1808B-PG uses a 28-pin plastic dual in-line package (PDIP) with through-hole mounting and RoHS-compliant lead finish. Pin functions follow JEDEC 32K×8 standard layout for seamless integration into existing SRAM/EEPROM footprints.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar nonvolatile parallel memory applications.

Compared with CY14B108L-SP25XI and AT28HC256-15PU, FM1808B-PG uniquely balances socket-based serviceability, 5V system compatibility, and true SRAM-like write performance - making it optimal for field-upgradeable industrial hardware where reliability and legacy interface preservation are mandatory.

Availability

FM1808B-PG is available at Aetrix Electronics and suitable for industrial energy metering, PLC data logging, medical device configuration storage, and avionics state capture requiring stable component supply across long product lifecycles.

Supply support for FM1808B-PG 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

Cypress Semiconductor (acquired Ramtron in 2012) is a U.S.-based semiconductor company specializing in nonvolatile memory, microcontrollers, and connectivity solutions for industrial and automotive markets.

The FM1808B-PG belongs to Ramtron's F-RAM product line, engineered specifically to replace battery-backed SRAM and slow EEPROM in applications demanding high write endurance, fast deterministic writes, and monolithic reliability without external components.

FAQ

Can FM1808B-PG be used as a direct pin-for-pin replacement for standard 32K×8 SRAMs?

No - while FM1808B-PG shares the JEDEC 32K×8 pinout and voltage levels, it requires /CE to strobe on every access (falling edge latches address), unlike SRAM where /CE may be held low. Memory controller timing must be updated to meet tAS = 0 ns and tAH = 15 ns, and /CE must track VDD via pullup during power transitions to prevent spurious writes.

What happens if /CE remains low across consecutive memory cycles?

Continuous /CE low violates the maximum /CE low time specification and prevents internal precharge, leading to undefined behavior or data corruption. Each cycle requires /CE high for ≥60 ns (tPC) to reset internal state. This is a fundamental architectural difference from SRAM and must be enforced in controller firmware or logic.

Does FM1808B-PG require special PCB layout considerations compared to SRAM?

Yes - due to its ferroelectric process sensitivity, minimize noise coupling on /CE, /WE, and VDD. Use a dedicated ground plane, keep /CE routing short and away from clocks/noisy signals, and place a 100 nF ceramic decoupling capacitor within 5 mm of VDD/VSS pins. Avoid shared return paths between memory and high-current peripherals.

How is data retention affected at temperatures above +75°C?

Data retention degrades exponentially with temperature: rated 38 years at +75°C, ~9 years at +85°C, and ~2.5 years at +105°C (extrapolated per Arrhenius model). For extended high-temp operation, derate usage or validate retention empirically - the device is only specified and guaranteed over 0°C to +85°C.