MCP79400/MCP79401/MCP79402
Battery-Backed I
2
C™ Real-Time Clock/Calendar with
SRAM and Protected EEPROM
Device Selection Table
Part Number
MCP79400
MCP79401
MCP79402
Protected EEPROM
Unprogrammed
EUI-48
™
EUI-64
™
Operating Ranges:
• 2-Wire Serial Interface, I
2
C™ Compatible
- I
2
C clock rate up to 400 kHz
• Temperature Range:
- Industrial (I): -40°C to +85°C
Timekeeping Features:
• Real-Time Clock/Calendar (RTCC):
- Hours, Minutes, Seconds, Day of Week, Day,
Month, Year
- Leap year compensated to 2399
- 12/24 hour modes
• Oscillator for 32.768 kHz Crystals:
- Optimized for 6-9 pF crystals
• On-Chip Digital Trimming/Calibration:
- ±1 PPM resolution
- ±129 PPM
• Dual Programmable Alarms
• Versatile Output Pin:
- Clock output with selectable frequency
- Alarm output
- General purpose output
• Power-Fail Time-Stamp:
- Time logged on switchover to and from
Battery mode
Packages:
• 8-Lead SOIC, MSOP, TSSOP and 2x3 TDFN
General Description:
The MCP7940X Real-Time Clock/Calendar (RTCC)
tracks time using internal counters for hours, minutes,
seconds, days, months, years, and day of week.
Alarms can be configured on all counters up to and
including months. For usage and configuration, the
MCP7940X supports I
2
C communications up to 400
kHz.
The open drain, multi-functional output can be
configured to assert on an alarm match, to output a
selectable frequency square wave, or as a general
purpose output.
The MCP7940X is designed to operate using a 32.768
kHz tuning fork crystal with external crystal load
capacitors. On-chip digital trimming can be used to
adjust for frequency variance caused by crystal
tolerance and temperature.
SRAM and timekeeping circuitry are powered from the
back-up supply when main power is lost, allowing the
device to maintain accurate time and the SRAM
contents. The times when the device switches over to
the back-up supply and when primary power returns
are both logged by the power-fail time-stamp.
The MCP7940X features 64 bits of EEPROM which is
only writable after an unlock sequence, making it ideal
for storing a unique ID or other critical information. The
MCP79401 and MCP79402 are pre-programmed with
EUI-48 and EUI-64 addresses, respectively. Custom
programming is also available.
Low-Power Features:
• Wide Voltage Range:
- Operating voltage range of 1.8V to 5.5V
- Backup voltage range of 1.3V to 5.5V
• Low Typical Timekeeping Current:
- Operating from V
CC
: 1.2 µA at 3.3V
- Operating from battery backup: 925 nA at
3.0V
• Automatic Switchover to Battery Backup
User Memory:
• 64-byte Battery-Backed SRAM
• 64-bit Protected EEPROM Area:
- Robust write unlock sequence
- EUI-48
™
MAC address (MCP79401)
- EUI-64
™
MAC address (MCP79402)
- Custom programming available
Package Types
SOIC, TSSOP, MSOP
TDFN
X1
X2
V
BAT
V
SS
1
2
3
4
8
7
6
5
V
CC
MFP
SCL
SDA
X1 1
X2 2
V
BAT
3
V
SS
4
8 V
CC
7 MFP
6 SCL
5 SDA
2011-2014 Microchip Technology Inc.
DS20005009D-page 1
MCP79400/MCP79401/MCP79402
1.0
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
(†)
V
CC
.............................................................................................................................................................................6.5V
All inputs and outputs (except SDA and SCL) w.r.t. V
SS
.....................................................................-0.6V to V
CC
+1.0V
SDA and SCL w.r.t. V
SS
............................................................................................................................... -0.6V to 6.5V
Storage temperature ...............................................................................................................................-65°C to +150°C
Ambient temperature with power applied................................................................................................-40°C to +125°C
ESD protection on all pins
4 kV
† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.
TABLE 1-1:
DC CHARACTERISTICS
Electrical Characteristics:
Industrial (I):
V
CC
= +1.8V to 5.5V
Min.
0.7 V
CC
—
0.05
V
CC
—
—
—
—
—
—
—
—
—
—
—
1.3
1.3
—
Typ.
(2)
—
—
—
Max.
—
0.3 V
CC
0.2 V
CC
—
Units
V
V
V
V
—
V
CC
2.5V
V
CC
< 2.5V
(Note
1)
T
A
= -40°C to +85°C
Conditions
DC CHARACTERISTICS
Param.
No.
D1
D2
D3
Sym.
V
IH
V
IL
V
HYS
Characteristic
High-level input voltage
Low-level input voltage
Hysteresis of Schmitt
Trigger inputs
(SDA, SCL pins)
Low-level output voltage
(MFP, SDA pins)
Input leakage current
Output leakage current
Pin capacitance
(SDA, SCL, MFP pins)
Oscillator pin
capacitance (X1, X2 pins)
EEPROM operating
current
SRAM/RTCC register
operating current
V
CC
data-retention cur-
rent (oscillator off)
Timekeeping current
Power-fail switchover
voltage
Backup supply voltage
range
Timekeeping backup
current
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
V
OL
I
LI
I
LO
C
IN
,
C
OUT
C
OSC
I
CCEERD
I
CCEEWR
I
CCREAD
I
CCWRITE
I
CCDAT
I
CCT
V
TRIP
V
BAT
I
BATT
—
—
—
—
3
—
—
—
—
—
1.2
1.5
—
—
925
0.40
±1
±1
10
—
400
3
300
400
1
—
1.7
5.5
850
1200
9000
V
A
A
pF
pF
A
mA
A
A
A
A
V
V
nA
nA
nA
I
OL
= 3.0 mA @ V
CC
= 4.5V
I
OL
= 2.1 mA @ V
CC
= 2.5V
V
IN
= V
SS
or V
CC
V
OUT
= V
SS
or V
CC
V
CC
= 5.0V
(Note
1)
T
A
= 25°C, f = 1 MHz
(Note
1)
V
CC
= 5.5V, SCL = 400 kHz
V
CC
= 5.5V
V
CC
= 5.5V, SCL = 400 kHz
V
CC
= 5.5V, SCL = 400 kHz
SCL, SDA, V
CC
= 5.5V
V
CC
= 3.3V
(Note
1)
—
(Note
1)
V
BAT
= 1.3V, V
CC
= V
SS
(Note
1)
V
BAT
= 3.0V, V
CC
= V
SS
(Note
1)
V
BAT
= 5.5V, V
CC
= V
SS
(Note
1)
Note 1:
2:
This parameter is not tested but ensured by characterization.
Typical measurements taken at room temperature.
2011-2014 Microchip Technology Inc.
DS20005009D-page 3
MCP79400/MCP79401/MCP79402
TABLE 1-2:
AC CHARACTERISTICS
Electrical Characteristics:
Industrial (I):
V
CC
= +1.8V to 5.5V
Characteristic
Clock frequency
Clock high time
Clock low time
SDA and SCL rise time
(Note
1)
SDA and SCL fall time
(Note
1)
Min.
—
—
4000
600
4700
1300
—
—
—
—
4000
600
4700
600
0
250
100
4000
600
—
—
4700
1300
—
—
300
0
—
1
1M
Typ.
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
32.768
—
—
Max.
100
400
—
—
—
—
1000
300
1000
300
—
—
—
—
—
—
—
—
—
3500
900
—
—
50
5
—
—
—
—
—
Units
kHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
T
A
= -40°C to +85°C
Conditions
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
(Note
3)
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
1.8V
V
CC
< 2.5V
2.5V
V
CC
5.5V
(Note
1)
—
(Note
1)
(Note
1)
—
(Note
1)
Page Mode, 25°C,
V
CC
= 5.5V
(Note
2)
AC CHARACTERISTICS
Param.
Symbol
No.
1
2
3
4
5
6
7
8
9
10
11
12
F
CLK
T
HIGH
T
LOW
T
R
T
F
T
HD
:
STA
Start condition hold time
T
SU
:
STA
Start condition setup time
T
HD
:
DAT
Data input hold time
T
SU
:
DAT
T
SU
:
STO
T
AA
T
BUF
Data input setup time
Stop condition setup time
Output valid from clock
Bus free time: Time the bus
must be free before a new
transmission can start
Input filter spike suppression
(SDA and SCL pins)
Write cycle time (byte or
page)
V
CC
fall time
V
CC
rise time
Oscillator frequency
Oscillator timeout period
Endurance
13
14
15
16
17
18
19
Note 1:
2:
3:
T
SP
T
WC
T
FVCC
T
RVCC
F
OSC
T
OSF
—
ns
ms
s
s
kHz
ms
cycles
Not 100% tested.
This parameter is not tested but ensured by characterization.
As a transmitter, the device must provide an internal minimum delay time to bridge the undefined region
(minimum 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
2011-2014 Microchip Technology Inc.
DS20005009D-page 5
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