REAL-TIME CLOCKS (I²C™ & SPI)A Feature Rich, Low Cost
Timekeeping Solution

Microchip offers a complete range of Real-Time Clock/Calendar (RTCC) products, from basic clocks with minimal features to highly integrated clocks with advanced timekeeping features and non-volatile memory in a single battery-backed device. By including onboard digital trimming in all RTCCs, accurate timekeeping over temperature is possible in cost sensitive as well as high-end applications.

Basic RTCCs
(I²C)
Mid-Range RTCCs
(I²C & SPI)
Upper Mid-Range RTCCs
(SPI)
Development
Tools

Basic RTCCs (I²C)

MCP7940M

The MCP7940M is a basic real-time clock that is low cost, but has the same timekeeping performance as Microchip’s mid-range MCP7941x family. With onboard digital trimming, this device is more accurate than other low cost RTCCs.

400 KHz I²C bus
Digital trimming = +/- 127 PPM
- Compensates up to ~11 sec/day
SRAM = 64 bytes

MCP7940N

The MCP7940N is a basic real-time clock that is low cost, but also has the same timekeeping performance and battery backup capabilities as Microchip’s mid-range MCP7941x family. With onboard digital trimming, this device is more accurate than other low cost RTCCs.

400 KHz I²C bus
Battery Switchover (VBAT)
Power-Fail Timestamp
Digital trimming = +/- 127 PPM
- Compensates up to ~11 sec/day
SRAM = 64 bytes

Part Number	Description	Datasheet
MCP7940M	Basic I²C RTCC with SRAM and without VBAT
MCP7940N	Basic I²C RTCC with SRAM
Note: 1 PPM is equivalent to approximately 86 milliseconds/day.

Mid-Range RTCCs (I²C & SPI)

MCP7941x & MCP7940x

The MCP7941x and MCP7940x are mid-range real-time clocks with advanced timekeeping features such as the Power-Fail Timestamp, which can be used to log the time and duration of power failures. With onboard digital trimming, these devices can provide accurate timekeeping over a wide temperature range.

400 KHz I²C bus
Battery Switchover (VBAT)
Power-Fail Timestamp
Digital trimming = +/- 127 PPM
- Compensates up to ~11 sec/day
SRAM = 64 bytes
EEPROM = 1K or 0K bits
Unique ID = 64 bits
- x = 0 Blank
- x = 1 EUI-48
- x = 2 EUI-64

MCP795xx

The MCP795xx are mid-range real-time clocks with a fast SPI bus to support millisecond alarms and advanced timekeeping features such as the “Power-Fail Timestamp” to log the time and duration of power failures. By expanding the digital trimming range in SPI RTCCs, accurate timekeeping over an even wider temperature range can be supported.

5 MHz SPI bus with millisecond alarm
Battery Switchover (VBAT)
Power-Fail Timestamp
Digital trimming = +/- 255 PPM
- Compensates up to ~22 sec/day
SRAM = 64 bytes
EEPROM = 2K or 1K bits
Unique ID= 128 bits
- x = 0 Blank
- x = 1 EUI-48
- x = 2 EUI-64

Part Number	Description	Datasheet
MCP7940x	Mid-range I²C RTCC with SRAM and Unique ID
MCP7941x	Mid-range I²C RTCC with SRAM, 1 Kbit EEPROM and Unique ID
MCP7951x	Mid-range SPI RTCC with SRAM, 1 Kbit EEPROM and Unique ID
MCP7952x	Mid-range SPI RTCC with SRAM, 2 Kbit EEPROM and Unique ID
Note: 1 PPM is equivalent to approximately 86 milliseconds/day.

Upper Mid-Range RTCCs (SPI)

MCP795Wxx

The MCP795Wxx are upper mid-range real-time clocks with a fast SPI bus to support millisecond alarms while including advanced timekeeping features such as the “Power-Fail Timestamp” to log power failures and the expanded digital trimming range to support extreme temperatures. With a Watchdog Timer and Event Detect Inputs in the RTCC, system power can be reduced while improving system robustness and efficiency.

5 MHz SPI bus with millisecond alarm
Battery Switchover (VBAT)
Power-Fail Timestamp
Digital trimming = +/- 255 PPM
- Compensates up to ~22 sec/day
Watchdog Timer (WDT)
2 Event Detect Inputs
- Programmable Pulse Count
- Programmable Debounce Timing
SRAM = 64 bytes
EEPROM = 2K or 1K bits
Unique ID = 128 bits
- x = 0 Blank
- x = 1 EUI-48
- x = 2 EUI-64

Part Number	Description	Datasheet
MCP795W2x	Upper mid-range SPI RTCC with SRAM, 2 Kbit EEPROM, Unique ID, Watchdog Timer and Dual Programmable Event Detect Inputs
MCP795W1x	Upper mid-range SPI RTCC with SRAM, 1 Kbit EEPROM, Unique ID, Watchdog Timer and Dual Programmable Event Detect Inputs
Note: 1 PPM is equivalent to approximately 86 milliseconds/day.

RTCC Development Tools

Real-Time Clock PICtail™ daughter board provides a low cost method of evaluating real-time clock functionality in standard development platforms. For additional functionality a coin cell holder and battery are included for backup power.

RTCC PICtail™ Board	Standard Development Platforms
MCP7941X PICtail™ Plus Daughter Board (I2C) MCP795W2X PICtailTM Plus Daughter Board (SPI)	Explorer 16 Development Board PICDEM™ PIC18 Explorer Board XLP 16-bit Development Board PICkit™ Serial Analyzer

Features

Highlighted Features	Results & Benefits
VBAT with Power-Fail Timestamp	Separate VBAT input pin with automatic switchover to backup power Timestamp logs the time when VCC is lost and when it is restored Time and Duration of power failures are easily determined
Timing Outputs	Dual alarms, but single output using either VCC or VBAT Clock output from 1 Hz to 32.768 KHz with Vcc only Longer MCU sleep cycles can be supported for lower overall power
Digital Trimming	Digital circuit compensates for crystal frequency drift over temperature Adds and subtracts clock pulses to maintain accurate time Accurate timekeeping supported over temperature
On Board Memory	64 Bytes SRAM, 1Kb or 2Kb EEPROM & 64 bit ID in a single RTCC Unique ID can be ordered blank or pre-programmed with MAC ID Wafer level programming: Lower cost & increased reliability of MAC ID
Watchdog Timer (WDT)	Dual programmable retriggers using SPI bus or digital input on WDT Separate hardware Reset output to MCU if WDT is not retriggered Robust system designs can require the WDT to be outside the MCU
Event Detect Inputs	A low speed input with debounce circuit for mechanical switches A high speed input with programmable pulse count setting Dual event detect inputs preserve MCU I/O pins & lower system power

Applications

How do you plan to use Real-Time Clock/Calendar in your application or design? Here are some examples of how RTCC Technology can take your applications to bigger and better places.

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Application Notes

Videos

MCP79400 Family of Real-Time Clock Chips

REAL-TIME CLOCKS (I²C™ & SPI)A Feature Rich, Low Cost
Timekeeping Solution