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STMicroelectronics M48T35-70PC1
- Part No.:
- M48T35-70PC1
- Manufacturer:
- STMicroelectronics
- Category:
- Real Time Clocks
- Package:
- 28-DIP Module (0.600", 15.24mm)
- Datasheet:
-
M48T35-70PC1.pdf
- Description:
- IC RTC CLK/CALENDAR PAR 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,493
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Product details
Overview
M48T35-70PC1 from STMicroelectronics is a monolithic 256 Kbit (32 Kb × 8) non-volatile TIMEKEEPER® SRAM integrating ultra-low-power static RAM, real-time clock, power-fail control circuitry, and lithium battery in a single CAPHAT™ DIP-28 package. It delivers BCD-coded timekeeping (year/month/day/hour/minute/second), automatic leap-year correction, frequency test output, and VPFD-triggered write protection at 4.5–4.75 V. Used in industrial control panels and legacy embedded systems requiring battery-backed time-stamped data logging.
For engineers reviewing the M48T35-70PC1 datasheet, M48T35-70PC1 pinout, M48T35-70PC1 application, or M48T35-70PC1 equivalent, key selection criteria include its JEDEC-compliant 32 Kb × 8 SRAM interface, integrated crystal-and-battery CAPHAT™ packaging, 70 ns access time, VCC noise immunity during power fail, and century-bit support for Y2K+ date handling.
Technical Context
The M48T35-70PC1 integrates a 32,768 Hz quartz oscillator, BiPORT™ dual-access memory array, and voltage-sense switching circuitry on a single die. Its clock registers (7FF8h–7FFFh) reside in the top 8 bytes of SRAM and are updated once per second by dedicated hardware - not software polling - ensuring atomic time updates independent of host bus activity.
Power management is handled autonomously: when VCC drops into the 4.5–4.75 V VPFD window, the device enters high-Z deselect mode and enables battery backup at VSO (typ. 4.25 V); the internal lithium cell sustains full SRAM retention and RTC operation for ≥7 years. Calibration uses five programmable bits (D4–D0 in 7FF8h) to adjust oscillator count rate via pulse blanking/splitting at the ÷256 stage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 256 Kbit (32 Kb × 8) non-volatile SRAM with battery-backed retention |
| Access time | 70 ns max - ensures compatibility with legacy 8-bit microcontrollers running at ≤14 MHz |
| RTC accuracy | ±35 ppm at 25 °C (±1.53 min/month); improves to +1/−2 ppm with calibration bits |
| VPFD range | 4.5 V ≤ VPFD ≤ 4.75 V - defines precise voltage window for automatic write-protection activation |
| Battery life | ≥7 years data/clock retention on internal lithium cell during VCC loss |
| Operating temp | 0 °C to +70 °C - validated for commercial-grade industrial control environments |
| Crystal interface | Integrated 32.768 kHz quartz crystal - no external load capacitors required |
Pinout & Package
Package: 28-pin plastic DIP (PCDIP28), 600 mil width, with integrated CAPHAT™ housing containing lithium button cell and quartz crystal.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address inputs | 15-bit address bus supporting full 32 Kb addressing (0000h–7FFFh) |
| DQ0–DQ7 | Data I/O bidirectional bus | Byte-wide parallel interface compatible with standard SRAM read/write timing |
| E | Chip enable | Active-low signal enabling memory access; controls power-fail detection sampling |
| G | Output enable | Active-low three-state control for DQ bus; must be high during WRITE to avoid contention |
| W | Write enable | Active-low signal initiating WRITE cycle; falling edge synchronizes data latch |
| VCC | Supply voltage | 5 V nominal (4.75–5.5 V); monitored continuously for VPFD/VSO transitions |
| VSS | Ground | Reference return path for both SRAM and RTC circuits |
Key Features
| Feature | Design Value |
|---|---|
| BYTEWIDE™ clock access | Time registers mapped to SRAM addresses 7FF8h–7FFFh - accessed using standard memory reads/writes without custom protocol |
| Automatic calendar correction | Hardware-level leap-year (2000, 2004…2096), month-end (28–31 day), and century-bit (CB/CEB) logic - no firmware overhead |
| Self-contained CAPHAT™ | Single-package integration of silicon, crystal, and battery eliminates board-level assembly complexity and reliability risks |
| Programmable oscillator calibration | 5-bit calibration register (D4–D0) enables ±31 count adjustments at ÷256 stage - achieves sub-ppm accuracy without external trim caps |
| Power-fail robustness | VPFD-triggered write protect + VSO switchover + tF-minimum fall time requirement prevents corruption during brownout transients |
Applications
| Industrial PLC HMI Panels | Legacy Medical Device Loggers |
|---|---|
Use Scenario: Maintaining accurate timestamps and configuration history across AC power cycles and firmware updates in DIN-rail mounted controllers. IC Role / Device Role / Timing Role: Non-volatile timekeeping and parameter storage - replaces discrete SRAM + RTC + battery + crystal solution. Use Value: Eliminates external backup capacitor aging concerns and guarantees 7-year timestamp integrity without periodic battery replacement. |
Use Scenario: Recording patient event logs (alarms, therapy start/stop) with legally traceable UTC timestamps in Class IIa diagnostic equipment. IC Role / Device Role / Timing Role: Primary RTC and audit trail memory - provides tamper-resistant, battery-backed BCD time registers compliant with IEC 62304 Annex C. Use Value: Century-bit support ensures correct year rollover through 2100; ±2 ppm calibrated accuracy meets FDA 21 CFR Part 11 timestamp precision requirements. |
| Point-of-Sale Terminal Clocks | Energy Meter Firmware Storage |
Use Scenario: Preserving transaction timestamps and tax-period counters during daily power-down cycles in retail kiosks operating on unregulated mains. IC Role / Device Role / Timing Role: Time source and secure configuration store - retains fiscal calendar state and last-sync time even after 30-day outage. Use Value: VPFD window (4.5–4.75 V) triggers write protection before brownout-induced bus glitches corrupt memory - critical for PCI-DSS audit logs. |
Use Scenario: Storing tariff schedules, demand-response commands, and meter calibration constants in utility-grade electricity meters deployed in remote substations. IC Role / Device Role / Timing Role: Long-life non-volatile memory + RTC co-processor - holds firmware patches and time-triggered billing parameters for >15 years. Use Value: Integrated SNAPHAT®-compatible design allows field-replacement of battery/crystal without PCB rework - reduces lifecycle maintenance cost by 65% vs. discrete solutions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar non-volatile timekeeping memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS12887A-70IND+ | 5 V, 128 Kbit (16 Kb × 8), 70 ns, integrated lithium battery & crystal; no calibration bits; century bit implemented differently (no CEB/CB register pair) | Lacks programmable oscillator calibration and has narrower VPFD window (4.25–4.5 V); requires external capacitor for VCC decoupling | Select if legacy socket compatibility with Dallas-era designs is mandatory and sub-ppm accuracy is not required. |
| M48T59Y-70PC1 | 5 V, 512 Kbit (64 Kb × 8), same CAPHAT™ DIP-28 package; adds 256-byte NVRAM for user configuration; identical RTC engine and calibration architecture | Provides double memory capacity and dedicated NVRAM block - suitable for systems needing persistent boot parameters alongside timekeeping | Select when additional non-volatile storage beyond time registers is needed without changing PCB layout or firmware drivers. |
Compared with DS12887A-70IND+, M48T35-70PC1 offers tighter RTC calibration and broader VPFD tolerance; compared with M48T59Y-70PC1, it trades memory density for lower cost and footprint in applications where 32 Kb suffices.
Availability
M48T35-70PC1 is available at Aetrix Electronics and suitable for industrial control panels, legacy medical loggers, point-of-sale terminals, and energy meter firmware storage requiring stable component supply over extended product lifecycles.
Supply support for M48T35-70PC1 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and memory ICs for industrial, automotive, and consumer markets.
The M48T35-70PC1 belongs to ST's TIMEKEEPER® family - engineered specifically for long-life, battery-backed timekeeping and data retention in mission-critical embedded systems where external RTC/SRAM integration increases failure risk.
FAQ
What is the function of the STOP bit in the seconds register?
The STOP bit (MSB of the seconds register at address 7FFFh) halts the 32.768 kHz oscillator to conserve battery current during shelf storage or prolonged standby. When cleared to '0', the oscillator resumes within 1 second. ST ships all M48T35-70PC1 units with STOP = '1' to maximize initial battery life. This bit operates independently of the READ/WRITE control bits.
How does the M48T35-70PC1 handle leap-year calculation?
Leap-year correction is performed entirely in hardware: the device automatically adjusts February length for years divisible by 4, excluding years divisible by 100 unless also divisible by 400 (e.g., 2000 is leap, 2100 is not). This logic applies to all dates written to the month/date registers and requires no firmware intervention - valid until year 2100.
Can the M48T35-70PC1 be used without the internal battery?
No - the CAPHAT™ DIP-28 package integrates the lithium battery and crystal as inseparable elements. Removing or disabling the battery voids data retention and RTC functionality. For battery-free operation, ST offers the SOIC variant (M48T35-70SO1) with separate SNAPHAT® housing - but the -70PC1 variant requires the integrated battery for specification compliance.
What happens during a power failure while writing to the time registers?
If VCC drops during a WRITE cycle to addresses 7FF8h–7FFFh, only the byte currently being written may become corrupted; the rest of the SRAM and RTC registers remain intact. The device's VPFD-triggered write protection activates within nanoseconds, freezing all further writes. Host firmware must implement atomic write sequences (e.g., halt clock → write all 8 bytes → restart) to ensure consistency.
M48T35-70PC1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- Timekeeper®
- Package/Case:
- 28-DIP Module (0.600", 15.24mm)
- Packaging:
- Tube
- Product Status:
- Active
- Programmable:
- Not Verified
- Type:
- Clock/Calendar
- Features:
- Leap Year
- Memory Size:
- -
- Time Format:
- HH:MM:SS (24 hr)
- Date Format:
- YY-MM-DD-dd
- Interface:
- Parallel
- Voltage - Supply:
- 4.75V ~ 5.5V
- Voltage - Supply, Battery:
- -
- Current - Timekeeping (Max):
- 2mA @ 4.75V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Through Hole
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 28-PCDIP, CAPHAT®
M48T35-70PC1 FAQ
1.How can I place an order for M48T35-70PC1 through Aetrix?
Please submit a Request for Quotation (RFQ) for M48T35-70PC1 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for M48T35-70PC1 reliable?
The price and inventory of M48T35-70PC1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M48T35-70PC1 is usually 5 days.
3.What payment methods are accepted for M48T35-70PC1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M48T35-70PC1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M48T35-70PC1?
M48T35-70PC1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M48T35-70PC1 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for M48T35-70PC1?
For technical support, including M48T35-70PC1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M48T35-70PC1 requirements.
6.How does Aetrix verify that M48T35-70PC1 is sourced from the original manufacturer or authorized distributors?
All M48T35-70PC1 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that M48T35-70PC1 meets industry standards.
7.What is the process for return or replacement of M48T35-70PC1?
All M48T35-70PC1 units undergo pre-shipment inspection (PSI). If there is an issue with M48T35-70PC1, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The M48T35-70PC1 part is unused and in its original packaging.
Return procedure for M48T35-70PC1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M48T35-70PC1 Tags
-
MCP7940N-I/SN
Microchip Technology
-
MCP7940MT-I/MNY
Microchip Technology
-
PCF85063ATL/1,118
NXP USA Inc.
-
MCP7940NT-I/SN
Microchip Technology
-
MCP7940NT-I/MS
Microchip Technology
-
MCP7940N-I/MS
Microchip Technology
-
PCF85063AT/AY
NXP USA Inc.
-
PCF85063TP/1Z
NXP Semiconductors
-
PCF85063ATT/AJ
NXP USA Inc.
-
MCP7940NT-E/SN
Microchip Technology
-
MCP7940NT-I/MNY
Microchip Technology
-
MCP79400T-I/SN
Microchip Technology
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