MCP7952X/MCP7951X
3V SPI Real-Time Clock Calendar with Battery Switchover
Device Selection Table User Memory:
SRAM EEPROM
64-Byte Battery-Backed SRAM
Part Number Unique ID
(Bytes) (Kbits)
2 Kbit and 1 Kbit EEPROM Memory:
MCP79520 64 2 Blank
- Software block write-protect (, , or entire
array)
MCP79510 64 1 Blank
- Write Page mode (up to 8 bytes)
MCP79521 64 2 EUI-48
- Endurance: 1M erase/write cycles
MCP79511 64 1 EUI-48
128-Bit Unique ID in Protected Area of EEPROM:
MCP79522 64 2 EUI-64
- Available blank or preprogrammed
MCP79512 64 1 EUI-64
- EUI-48 or EUI-64 MAC address
Timekeeping Features:
- Unlock sequence for user programming
Real-Time Clock/Calendar:
Operating Ranges:
- Hours, Minutes, Seconds, Hundredth of
Seconds, Day of Week, Month, Year, Leap
SPI Clock Speed up to 5 MHz
Year
Operating Temperature Ranges:
Crystal Oscillator requires External 32,768 kHz
- Industrial (I Temp): -40C to +85C.
Tuning Fork Crystal and Load Capacitors.
Packages include 10-Lead MSOP and TDFN
Clock Out Function:
- 1Hz, 4.096 kHz, 8.192 kHz, 32.768 kHz
Package Types (not to scale)
2 Programmable Alarms
MSOP/TDFN
Programmable open drain output Alarm or
Interrupt X1 1 10 Vcc
On-Chip Digital Trimming/Calibration:
X2 2 9 MFP
- +/- 255 PPM range in 1 PPM steps VBAT 3 8 SCK
Power-Fail Time-Stamp @ Battery Switchover: 4 7 SO
CS
- Logs time when VCC fails and VCC is restored
5 6 SI
VSS
Low-Power Features:
Wide Operating Voltage:
Note: MCP795XX is used in this document as a
-VCC: 1.8V to 3.6V
generic part number for the MCP7951X,
MCP7952X devices.
-VBAT: 1.3V to 3.6V
Low Operating Current:
-VCC Standby Current < 1uA @ 3V
-VBAT Timekeeping Current: <700nA @ 1.8V
Automatic Battery Switchover from VCC to VBAT:
- Backup power for timekeeping and SRAM
retention
2012 Microchip Technology Inc. Preliminary DS22300A-page 1
MCP795XXMCP7952X/MCP7951X
Description:
The MCP795XX is a low-power Real-Time Clock/
Calendar (RTCC) that uses digital trimming compen-
sation for an accurate clock/calendar, an interrupt out-
put to support alarms and events, a power sense
circuit that automatically switches to the backup sup-
ply, nonvolatile memory for safe data storage and sev-
eral enhanced features that support system
requirements.
Along with a low-cost 32,768 kHz crystal, this RTCC
tracks time using several internal registers and then
communicates the data over a 5 MHz SPI bus that is
fast enough to support a programmable millisecond
alarm.
The device is fully accessible through the serial inter-
CC is between 1.8V and 3.6V, but can
face, while V
operate down to 1.3V through the backup supply con-
nected to the VBAT input for timekeeping and SRAM
retention only.
As part of the power sense circuit, a time saver
function is implemented to store the time when main
power is lost and again, when power is restored to log
the duration of a power failure.
Along with the on-board serial EEPROM and battery-
backed SRAM, a 128-bit protected space is available
for a unique ID. This space can be ordered
preprogrammed with a MAC address, or blank for the
user to program.
This clock/calendar automatically adjusts for months
with fewer than 31 days including corrections for leap
years. The clock operates in either 24-hour or 12-hour
format with AM/PM indicator and settable alarm(s).
Using the external crystal, the MFP pin can be set to
generate a number of output frequencies.
FIGURE 1-1: BLOCK DIAGRAM
X1 VCC
CLKOUT Divider
OSC
X2 MFP
EEPROM
VBAT SCK
ID
CS SO
SRAM
SPI
VSS SI
TIME-STAMP
DS22300A-page 2 Preliminary 2012 Microchip Technology Inc.
VBAT
ALARMS
SWITCHOVER