Microchip Technology MCP795B21T-I/SL

Overview

MCP795B21T-I/SL 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 at power-up. It supports digital trimming (±255 ppm), dual programmable alarms, power-fail time-stamping, and operates from 1.8V to 5.5V VCC or 1.3V to 5.5V VBAT for continuous timekeeping in industrial metering and backup-power-critical systems.

For engineers reviewing the MCP795B21T-I/SL datasheet, MCP795B21T-I/SL pinout, MCP795B21T-I/SL application, or MCP795B21T-I/SL equivalent, key selection considerations include its 32 kHz boot-clock capability (MCP795BXX variant), VBAT switchover behavior, CLKOUT/BOOT dual-function pin, alarm resolution down to hundredths of seconds, and EUI-48™ preprogrammed ID location in protected EEPROM space.

Technical Context

The MCP795B21T-I/SL implements a crystal-based RTCC with on-chip oscillator driving internal timekeeping registers in BCD format, supporting automatic leap-year correction and 12/24-hour mode. Its SPI interface operates up to 10 MHz across 1.8–5.5V, with CS-controlled standby and high-impedance SO during deselect.

It integrates three independent timing subsystems: a main RTCC engine with digital calibration, a programmable watchdog timer with dedicated WDO output and dual retrigger (SPI/EVHS), and two event detect inputs-EVHS (pulse-counting: 1st/4th/16th/32nd edge) and EVLS (debounced: 31 ms / 500 ms)-both functional under VCC or VBAT.

Key Specifications

Pinout & Package

Package: 14-lead SOIC (Small Outline Integrated Circuit), 3.9 mm × 8.7 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 MCP795B20T-I/SL, the MCP795B21T-I/SL adds factory-programmed EUI-48™ for secure device identification, while DS3231SN#T&R trades EEPROM, event inputs, and SPI for superior ±2 ppm accuracy via integrated TCXO-making it unsuitable for applications requiring programmable alarms or local nonvolatile storage.

Availability

MCP795B21T-I/SL is available at Aetrix Electronics and suitable for smart metering, industrial HMI, medical infusion pumps, and building automation controllers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for MCP795B21T-I/SL 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, mixed-signal, analog, and Flash-IP solutions, serving automotive, industrial, consumer, and communications markets with high-reliability silicon and development tools.

The MCP795XXX product line delivers highly integrated SPI RTCs with battery switchover, nonvolatile memory, and enhanced peripherals-designed specifically for embedded systems needing robust timekeeping, event logging, and identity management without host CPU overhead.

FAQ

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

The CLKOUT/BOOT pin on the MCP795B21T-I/SL serves a dual role: as a programmable clock output (1 Hz, 4.096 kHz, 8.192 kHz, or 32.768 kHz) during normal operation, and as a fixed 32 kHz square-wave boot-up clock asserted immediately at power-on reset-exclusive to MCP795BXX variants like the MCP795B21T-I/SL. This ensures deterministic timebase availability before host firmware initializes.

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

The MCP795B21T-I/SL automatically switches from VCC to VBAT when VCC drops below 1.3–1.7V, preserving RTC registers and 64-byte SRAM contents. It logs the exact time of VCC failure and restoration in dedicated power-down/power-up timestamp registers (0x18–0x1F), accessible via SPI read without host intervention-enabling accurate outage duration tracking in the MCP795B21T-I/SL.

Does the MCP795B21T-I/SL support both 12-hour and 24-hour time formats?

Yes, the MCP795B21T-I/SL supports both formats via the 12/24 bit (bit 6 of register 0x03). Clearing this bit selects 24-hour mode; setting it enables 12-hour mode with AM/PM indication encoded in bits 5–4. The timekeeping engine automatically handles leap-year correction and month-end rollover regardless of format, and the MCP795B21T-I/SL retains full functionality in either mode.

What is the purpose of the EUI-48™ unique ID in the MCP795B21T-I/SL?

The EUI-48™ unique ID is a factory-programmed 128-bit identifier stored in protected EEPROM space, compliant with IEEE standards for MAC addressing. It enables secure device authentication, firmware binding, and network-level traceability. Accessed via IDREAD instruction, it eliminates external ID storage and is locked until unlocked with a specific sequence-providing tamper-resistant identity in the MCP795B21T-I/SL.

Can the MCP795B21T-I/SL operate solely from VBAT without VCC applied?

Yes-the MCP795B21T-I/SL maintains timekeeping and SRAM retention using only VBAT (1.3V–5.5V) when VCC is absent. However, SPI communication, EEPROM writes, alarm configuration, and event detection require VCC. All RTCC registers remain accessible and increment under VBAT alone, and the MCP795B21T-I/SL resumes full functionality-including IRQ generation and CLKOUT-immediately upon VCC restoration.