Microchip Technology MCP795B21T-I/ST

Overview

MCP795B21T-I/ST from Microchip Technology is a SPI real-time clock/calendar (RTCC) IC with integrated 64-byte battery-backed SRAM, 2 Kbit EEPROM, EUI-48™ unique ID, and 32 kHz boot-up clock on CLKOUT/BOOT pin. It delivers timekeeping accuracy via digital trimming (±255 ppm in 1 ppm steps), supports dual programmable alarms, power-fail time-stamping, and operates from 1.8V to 5.5V VCC or 1.3V to 5.5V VBAT for backup retention. Used in industrial metering, smart sensors, and battery-powered IoT edge nodes requiring precise timestamped event logging.

For engineers reviewing the MCP795B21T-I/ST datasheet, MCP795B21T-I/ST pinout, MCP795B21T-I/ST application, or MCP795B21T-I/ST equivalent, key selection criteria include its 32 kHz boot-up capability, VBAT switchover voltage threshold (1.3–1.7 V), <700 nA timekeeping current at 1.8 V, 10 MHz SPI interface, and dual event detect inputs (EVHS/EVLS) with configurable debounce and pulse counting.

Technical Context

The MCP795B21T-I/ST implements a crystal-based RTCC core with digital calibration logic that adjusts timekeeping by ±255 ppm in 1 ppm increments per minute. Its oscillator requires an external 32.768 kHz tuning fork crystal connected to X1/X2, and it supports both 12- and 24-hour formats with automatic leap-year correction.

It integrates three independent timing subsystems: a primary RTCC engine with hundredth-of-second resolution, two programmable alarms (Alarm 0 with second-level, Alarm 1 with hundredth-of-second resolution), and a dedicated watchdog timer with dual retrigger sources (SPI or EVHS). All registers, SRAM, and EEPROM retain state during VCC-to-VBAT switchover triggered at 1.3–1.7 V.

Key Specifications

Pinout & Package

Package: 14-lead SOIC (Small Outline Integrated Circuit), 3.9 mm × 8.65 mm body, 1.27 mm pitch, RoHS-compliant, rated for -40°C to +85°C industrial operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock/calendar applications.

Compared with MCP795W21T-I/ST, the MCP795B21T-I/ST adds guaranteed 32 kHz clock output at power-up-critical for deterministic boot sequences-while retaining identical memory, ID, and alarm capabilities. Against DS3231M+, it trades ±2 ppm TCXO stability for richer peripheral integration (SPI, dual event inputs, programmable alarms) and lower VBAT current, at the cost of external crystal dependency.

Availability

MCP795B21T-I/ST is available at Aetrix Electronics and suitable for industrial metering, battery-powered data loggers, medical wearables, and secure IoT gateways requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for MCP795B21T-I/ST 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

Microchip Technology Inc. is a leading provider of microcontroller, analog, FPGA, and timing solutions, serving automotive, industrial, consumer, and communications markets with vertically integrated silicon and development tools.

The MCP795XXX product line delivers highly integrated SPI real-time clock/calendars with battery switchover, nonvolatile memory, and enhanced system monitoring features-designed specifically for resource-constrained embedded systems needing autonomous, low-power timekeeping and event response.

FAQ

What is the function of the CLKOUT/BOOT pin on the MCP795B21T-I/ST?

The CLKOUT/BOOT pin on the MCP795B21T-I/ST is a push-pull output that defaults to a 32.768 kHz square wave at power-up-providing immediate timing reference before the host MCU initializes. It is programmable to output 1 Hz, 4.096 kHz, 8.192 kHz, or 32.768 kHz, and supports calibration-adjusted frequencies. This boot-up capability distinguishes the MCP795B21T-I/ST from the W-series variants and eliminates startup delays in time-critical applications.

How does the MCP795B21T-I/ST handle power failure and recovery?

The MCP795B21T-I/ST automatically switches from VCC to VBAT when VCC drops below 1.3–1.7 V, preserving RTC registers, 64-byte SRAM, and EEPROM contents. Crucially, it logs the exact time of VCC failure and restoration into dedicated 16-byte power-down/power-up timestamp registers-enabling precise outage duration tracking without MCU involvement. The MCP795B21T-I/ST resumes timekeeping seamlessly upon VCC return.

Does the MCP795B21T-I/ST require external components for basic operation?

Yes-the MCP795B21T-I/ST requires an external 32.768 kHz tuning fork crystal connected between X1 and X2, plus two load capacitors (typically 12.5 pF each) referenced to ground. It also needs external pull-up resistors on WDO and IRQ (to VCC or VBAT), and a backup battery (1.3–5.5 V) on VBAT. No external oscillator is needed, as the internal circuit drives the crystal directly.

What unique identifier is provided with the MCP795B21T-I/ST, and how is it accessed?

The MCP795B21T-I/ST includes a factory-programmed 128-bit EUI-48™ MAC address stored in a protected EEPROM region. It is accessed via the SPI interface using the IDREAD instruction (0b00110011) after issuing the UNLOCK instruction (0b00010100). The ID space is write-protected by default and requires a specific unlock sequence to enable user programming-ensuring tamper-resistant device identity for secure provisioning and traceability.

Can the MCP795B21T-I/ST generate interrupts for external events without MCU polling?

Yes-the MCP795B21T-I/ST features two dedicated event detect inputs: EVHS (high-speed, edge-triggered, pulse-counting for 1st/4th/16th/32nd event) and EVLS (low-speed, debounced with 31 ms or 500 ms filter). Both operate from VCC or VBAT and assert the shared IRQ pin on detection-enabling true hardware offload of switch monitoring, pulse counting, or fault signaling without CPU polling or wake-up overhead.