M48T128Y and M48T128V are ST's ultra-low-power SRAM, real-time clock, power-fail control circuit, battery and crystal integrated units. The device has BCD coded year, month, day, date, hours, minutes and seconds, automatic power-fail chip deselection and write protection, can perform conventional SRAM operation, unlimited write cycles, software controlled clock calibration, and can achieve 10 years of data storage and clock operation in the absence of power. It comes with a battery and crystal, and is compatible with JEDEC standard 128Kx8 SRAMs.
The M48T128Y/V TIMEKEEPER® SRAM combines a 128 Kb × 8 non‑volatile static RAM with a real‑time clock, integrated battery, and crystal in a 32‑pin PMDIP package. It offers ultra‑low power operation, automatic power‑fail chip deselect, write protection, and unlimited write cycles, making it a drop‑in replacement for standard 128 Kb × 8 SRAMs.
The handbook describes the device’s operation modes (READ, WRITE, Data Retention, Clock), timing characteristics, pin assignments, and electrical ratings. It also provides ordering information, mechanical dimensions, and revision history for the two voltage variants (5 V and 3.3 V).
| Supply Voltage (M48T128Y) | 4.5 to 5.5 V |
|---|---|
| Supply Voltage (M48T128V*) | 3.0 to 3.6 V |
| Write‑Protect Voltage (M48T128Y) | 4.1 V < Vprp < 4.5 V |
| Write‑Protect Voltage (M48T128V*) | 2.7 V < Veep < 3.0 V |
| Data Retention (no power) | 10 years |
| Write Cycle Capability | Unlimited |
The M48T128Y operates from 4.5 V to 5.5 V.
It includes an automatic power‑fail chip deselect and write‑protection circuit that switches to the backup battery when Vcc drops.
The device can retain data for up to 10 years without power.
The write‑protect voltage for the M48T128V* must be between 2.7 V and 3.0 V.