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STMicroelectronics M48T86MH1F
- Part No.:
- M48T86MH1F
- Manufacturer:
- STMicroelectronics
- Category:
- Real Time Clocks
- Package:
- 28-SOP (0.350", 8.89mm Width) with SNAPHAT Sockets
- Datasheet:
-
M48T86MH1F.pdf
- Description:
- IC RTC CLK/CALENDAR PAR 28SOH
- Quantity:
- Payment:
- Shipping:
Inventory:1,030
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Product details
Overview
M48T86MH1F from STMicroelectronics is a 5.0 V real-time clock/calendar IC with integrated lithium battery and quartz crystal in a CAPHAT™ DIP-24 package. It provides non-volatile timekeeping (seconds to years with leap-year compensation), 128-byte RAM (14 registers + 114 general-purpose bytes), selectable Intel/Motorola bus timing, and three software-maskable interrupts - used as drop-in replacement for legacy PC motherboard RTCs.
For engineers reviewing the M48T86MH1F datasheet, M48T86MH1F pinout, M48T86MH1F application, or M48T86MH1F equivalent, key selection criteria include ±1 minute/month clock accuracy, self-contained power backup, SQW programmability (122 µs–500 ms periodic rates), IRQ open-drain interrupt architecture, and compatibility with bq3285/7A and DS12887 designs.
Technical Context
The M48T86MH1F integrates a 32.768 kHz quartz oscillator with ≤23 ppm error at 25°C, enabling ±1 minute/month timekeeping accuracy. Its dual-bus interface supports Intel-style (AS/DS/R/W) and Motorola-style (E/R/W/MOT) protocols via pin-strapped MOT selection.
Internal logic includes double-buffered clock/calendar registers updated every second, four independent interrupt sources (alarm, periodic, update-ended, SQW), and register-mapped control of oscillator enable, square wave output frequency, daylight savings, and 24/12-hour mode - all accessible through AD0–AD7 multiplexed address/data bus.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 5.0 V nominal; device automatically deselects below VPFD to preserve RAM integrity during brownout. |
| Clock Accuracy | ±1 minute per month (≤23 ppm oscillator error at 25°C); enables long-term calendar reliability without external calibration. |
| RAM Capacity | 128 bytes total: 14 dedicated clock/control registers + 114 general-purpose non-volatile SRAM bytes. |
| Interrupt Types | Three maskable interrupts: time-of-day alarm (1 s–1 day), periodic (122 µs–500 ms), and update-ended cycle - each with flag and enable bits in Registers B/C. |
| Square Wave Output | Programmable SQW frequency (13 selectable taps); enabled/disabled via SQWE bit; not active when VCC < VPFD. |
| Bus Interface | Multiplexed AD0–AD7 address/data bus with AS/DS/E/R/W/MOT control; pin-selectable Intel or Motorola timing protocol. |
| Data Retention | 10 years minimum with integrated lithium battery and crystal; no external backup required. |
Pinout & Package
Package: 24-pin plastic DIP (PCDIP24) with integrated CAPHAT™ housing containing lithium battery and 32.768 kHz crystal. Dimensions: 600 mil width, standard DIP footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Power supply input | 5.0 V main supply; triggers automatic write protection when voltage drops below VPFD. |
| VSS | Ground reference | System ground return path; internal pull-down on MOT referenced to this pin. |
| AD0–AD7 | Multiplexed address/data bus | Shared 8-bit bidirectional path for register addressing and data transfer; latched by AS/DS edges. |
| AS | Address strobe input | Falling edge latches address from AD0–AD7; initiates first phase of bus cycle. |
| DS | Data strobe input (READ) | Falling edge enables data output during READ; functions as memory-style output enable. |
| E | Chip enable input | Active-low enable; must be asserted for any bus access; prevents spurious writes during reset. |
| R/W | Read/write control | High = READ, low = WRITE; controls direction of AD0–AD7 data flow and internal latch timing. |
| MOT | Bus mode select | High = Motorola timing, low/disconnected = Intel timing; internal 20 kΩ pull-down ensures default Intel mode. |
| IRQ | Interrupt request output | Open-drain output requiring external pull-up; asserts low when enabled interrupt condition occurs. |
| SQW | Square wave output | Programmable frequency output (13 taps); disabled when VCC < VPFD or SQWE = 0. |
| RST | Reset input | Active-low asynchronous reset; clears all interrupt flags, enables, and SQWE; blocks access until released. |
| RCL | RAM clear input | Held low ≥100 ms clears 114 RAM bytes to 0xFF; no effect on clock registers or battery load. |
| NC | No connect | Pins 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 - internally unconnected; must be left floating. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated CAPHAT™ DIP-24 package | Self-contained 5 V RTC with lithium battery and 32.768 kHz crystal in single through-hole footprint - eliminates discrete backup design effort. |
| 128-byte non-volatile RAM | 14 clock/control registers + 114 user-accessible bytes retained for 10+ years without external power - enables firmware state persistence across power cycles. |
| Selectably timed bus interface | Hardware-mode selection (Intel/Motorola) via MOT pin - supports legacy x86 and embedded microcontroller platforms without glue logic. |
| Triple software-maskable interrupts | Independent enable/flag bits for alarm, periodic, and update-ended events - allows precise event scheduling without polling overhead. |
| Programmable square wave output | 13-frequency SQW generator (122 µs–500 ms) controlled by Register A - replaces external timing oscillators in watchdog or clock-synchronization circuits. |
Applications
| Legacy PC Motherboard RTC | Industrial Control Panel Clock |
|---|---|
|
Use Scenario: Replacing aging DS12887 or bq3285-based RTCs on AT/ATX motherboard designs requiring long-life timekeeping and BIOS compatibility. IC Role / Device Role / Timing Role: Primary real-time clock/calendar with battery-backed RAM for CMOS setup storage and OS time services. Use Value: Pin- and function-compatible drop-in replacement preserving existing PCB layout and firmware register mapping. |
Use Scenario: Providing accurate timestamping and scheduled event triggering in DIN-rail mounted PLCs and HMI panels operating in unattended environments. IC Role / Device Role / Timing Role: Standalone time-of-day source with alarm interrupt for logging, maintenance alerts, and batch process scheduling. Use Value: 10-year data retention eliminates need for external supercapacitors or battery management circuitry. |
| Medical Device Power-Fail Logger | Point-of-Sale Terminal Calendar |
|
Use Scenario: Capturing last-known operational state and timestamp during unexpected AC loss in infusion pumps or diagnostic analyzers. IC Role / Device Role / Timing Role: Non-volatile timekeeper and RAM buffer activated during VCC brownout to record critical fault timestamps. Use Value: Automatic write protection below VPFD ensures RAM contents remain intact even during rapid power collapse. |
Use Scenario: Maintaining accurate date/time across daily power cycles in retail POS terminals with no network time sync. IC Role / Device Role / Timing Role: Primary calendar subsystem supporting receipt printing, transaction logging, and shift reporting. Use Value: Leap-year compensation and century rollover support ensure correct date calculation through year 2100. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar real-time clock/calendar applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS12887 | Same 24-pin DIP footprint and register map; uses external battery and crystal; no integrated CAPHAT™ housing. | Requires separate battery holder and crystal layout; higher BOM count and assembly complexity. | Choose DS12887 only if redesigning for cost-sensitive, non-integrated backup or legacy repair stock. |
| bq3287 | Pin-compatible but uses I²C interface instead of parallel bus; lacks RCL pin and MOT bus select; different register layout. | Requires firmware rewrite for I²C driver and register access; no direct Intel/Motorola timing support. | Choose bq3287 only when migrating to serial interface and accepting full software revalidation. |
Compared with DS12887, M48T86MH1F reduces board space and assembly steps via integrated CAPHAT™; compared with bq3287, it preserves legacy parallel bus firmware compatibility while offering superior interrupt flexibility and RAM accessibility during clock updates.
Availability
M48T86MH1F is available at Aetrix Electronics and suitable for legacy PC motherboard replacements, industrial control panel upgrades, and medical device power-fail logging requiring stable component supply and long-term lifecycle continuity.
Supply support for M48T86MH1F 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, specializing in microcontrollers, power management, sensors, and timing solutions for industrial, automotive, and consumer markets.
M48T86MH1F belongs to ST's legacy real-time clock product line designed specifically for drop-in replacement of industry-standard PC RTCs with integrated backup power - targeting long-lifecycle, low-maintenance embedded systems.
FAQ
Is M48T86MH1F RoHS compliant?
Yes, M48T86MH1F is RoHS compliant with lead-free second-level interconnects. It meets EU Directive 2011/65/EU requirements and carries appropriate marking per STMicroelectronics' environmental documentation (Rev 7, December 2008). No exemptions apply to its CAPHAT™ DIP-24 construction.
Can M48T86MH1F operate without the integrated battery?
No - the integrated lithium battery is essential for continuous timekeeping and RAM retention during VCC loss. The device will maintain time and data only when the CAPHAT™ housing is fully assembled and functional. Removing or disabling the battery voids the 10-year retention guarantee and causes clock stoppage upon power removal.
What happens to the clock during a VCC brownout?
When VCC drops below the power-fail deselect voltage (VPFD), the M48T86MH1F automatically disables write access and enters battery-backup mode. The oscillator continues running, timekeeping proceeds uninterrupted, and RAM contents remain preserved - ensuring no time or data loss during transient supply dips.
How is the SQW output frequency selected?
SQW frequency is selected by programming bits RS3–RS0 in Register A (address 0Ah), which chooses one of 13 oscillator divider taps ranging from 122 µs to 500 ms. The SQWE bit (Register B, bit 3) must be set to 1 to enable output; SQW is inactive when VCC < VPFD regardless of register settings.
M48T86MH1F Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 28-SOP (0.350", 8.89mm Width) with SNAPHAT Sockets
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Clock/Calendar
- Features:
- Alarm, Leap Year, NVSRAM, Square Wave Output
- Memory Size:
- 114B
- Time Format:
- HH:MM:SS (12/24 hr)
- Date Format:
- YY-MM-DD-dd
- Interface:
- Parallel
- Voltage - Supply:
- 4.5V ~ 5.5V
- Voltage - Supply, Battery:
- -
- Current - Timekeeping (Max):
- 15mA @ 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 28-SOH
M48T86MH1F FAQ
1.How can I place an order for M48T86MH1F through Aetrix?
Please submit a Request for Quotation (RFQ) for M48T86MH1F 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 M48T86MH1F reliable?
The price and inventory of M48T86MH1F are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M48T86MH1F is usually 5 days.
3.What payment methods are accepted for M48T86MH1F?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M48T86MH1F transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M48T86MH1F?
M48T86MH1F orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M48T86MH1F 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 M48T86MH1F?
For technical support, including M48T86MH1F datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M48T86MH1F requirements.
6.How does Aetrix verify that M48T86MH1F is sourced from the original manufacturer or authorized distributors?
All M48T86MH1F 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 M48T86MH1F meets industry standards.
7.What is the process for return or replacement of M48T86MH1F?
All M48T86MH1F units undergo pre-shipment inspection (PSI). If there is an issue with M48T86MH1F, 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 M48T86MH1F part is unused and in its original packaging.
Return procedure for M48T86MH1F:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M48T86MH1F 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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