MCP79400/MCP79401/MCP79402
I
2
C™ Real-Time Clock/Calendar with SRAM, Unique ID
and Battery Switchover
Device Selection Table
Part Number
MCP79400
MCP79401
MCP79402
SRAM
(Bytes)
64
64
64
Unique ID
Blank
EUI-48
™
EUI-64
™
Description:
The MCP7940X series of low-power Real-Time Clocks
(RTC) uses digital timing compensation for an accurate
clock/calendar, a programmable output control for
versatility, a power sense circuit that automatically
switches to the backup supply, and nonvolatile memory
for data storage. Using a low-cost 32.768 kHz crystal,
it tracks time using several internal registers. For
communication, the MCP7940X uses the I
2
C™ bus.
The clock/calendar automatically adjusts for months
with fewer than 31 days, including corrections for
leap years. The clock operates in either the 24-hour
or 12-hour format with an AM/PM indicator and
settable alarm(s) to the second, minute, hour, day of
the week, date or month. Using the programmable
CLKOUT, frequencies of 32.768, 8.192 and 4.096
kHz and 1 Hz can be generated from the external
crystal.
Along with the battery-backed SRAM memory, a 64-bit
protected EEPROM space is available for a unique ID
or MAC address to be programmed at the factory or by
the end user.
The device is fully accessible through the serial
interface while V
CC
is between 1.8V and 5.5V, but can
operate down to 1.3V for timekeeping and SRAM
retention only.
The RTC series of devices are available in the standard
8-lead SOIC, TSSOP, MSOP and 2x3 TDFN packages.
Features:
• Real-Time Clock/Calendar (RTCC), Battery
Backed:
- Hours, Minutes, Seconds, Day of Week, Day,
Month and Year
- Dual alarm with single output
• On-Chip Digital Trimming/Calibration:
- Range -127 to +127 ppm
- Resolution 1 ppm
• Programmable Open-Drain Output Control:
- CLKOUT with 4 selectable frequencies
- Alarm output
• 64 Bytes SRAM, Battery Backed
• 64-Bit Unique ID:
- User or factory programmable
- Protected EEPROM
- EUI-48
™
or EUI-64
™
MAC address
- Custom ID programming
• Automatic V
CC
Switchover to V
BAT
Backup
Supply
• Power-Fail Time-Stamp for Battery Switchover
• Low-Power CMOS Technology:
- Dynamic Current: 400
A
max read
- Dynamic Current: 400
A
max SRAM
- Battery Backup Current: <700nA @ 1.8V
• 100 kHz and 400 kHz Compatibility
• ESD Protection >4,000V
• 1 Million Erase/Write Cycles for Unique ID
• Packages include 8-Lead SOIC, TSSOP, 2x3
TDFN, MSOP
• Pb-Free and RoHS Compliant
• Temperature Ranges:
- Industrial (I): -40°C to +85°C
Package Types
MSOP
X1
X2
V
BAT
V
SS
1
2
3
4
8
7
6
5
SOIC, TSSOP
X1
X2
V
BAT
V
SS
1
2
3
4
8
7
6
5
V
CC
MFP
SCL
SDA
V
CC
MFP
SCL
SDA
X1 1
X2 2
V
BAT
3
V
SS
4
TDFN
8 V
CC
7 MFP
6 SCL
5 SDA
2011 Microchip Technology Inc.
DS25009C-page 1
MCP7940X
1.0
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
(†)
V
CC
.............................................................................................................................................................................6.5V
All inputs and outputs w.r.t. V
SS
..........................................................................................................-0.6V to V
CC
+1.0V
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
—
—
—
—
—
—
—
—
—
—
—
V
BAT
Change Over
V
CC
Fall Time
(Note
1)
V
CC
Rise Time
(Note
1)
V
BAT
Voltage Range
(Note
1)
Oscillator Pin
Capacitance
1.3
300
0
1.3
—
3
700
5
Typ.
Max.
—
—
0.3 V
CC
0.2 V
CC
—
Units
—
V
V
V
—
—
V
CC
= 2.5V to 5.5V
(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
SCL, SDA pins
High-level input voltage
Low-level input voltage
Hysteresis of Schmitt
Trigger inputs
(SDA, SCL pins)
Low-level output voltage
(MFP, SDA)
Input leakage current
Output leakage current
Pin capacitance
(SDA, SCL and MFP)
D4
D5
D6
D7
D8
D9
D10
D11
V
OL
I
LI
I
LO
C
IN
,
C
OUT
0.40
±1
±1
10
400
3
300
400
1
—
—
1.7
—
—
5.5
—
V
A
A
pF
A
mA
A
A
A
nA
A
V
s
s
V
pF
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 = 400 kHz
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
V
CC
= 5.5V, SCL = SDA = V
CC
V
BAT
= 1.8V @ 25°C,
Figure 2-1
V
CC
= 3.6V @ 25°C,
Figure 2-2
(Note
2)
1.5V typical at T
AMB
= 25°C
From V
TRIP
(max) to V
TRIP
(min)
From V
TRIP
(min) to V
TRIP
(max)
—
(Note
1)
I
CC
Read Operating current
I
CC
Write ID
I
CC
Read Operating current
I
CC
Write SRAM
I
CCS
I
BAT
IV
CC
Standby current
Operating Current
D12
D13
D14
D15
D16
Note 1:
2:
VTRIP
VCCFT
VCCRT
V
BAT
COSC
This parameter is periodically sampled and not 100% tested.
Standby with oscillator running.
2011 Microchip Technology Inc.
DS25009C-page 3
MCP7940X
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
—
—
1M
Max.
100
400
—
—
—
—
1000
300
1000
300
—
—
—
—
—
—
—
—
—
3500
900
—
—
50
5
—
Units
kHz
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
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
and
Note 2)
—
25°C, V
CC
= 5.5V Page mode
(Note
3)
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
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)
Endurance
13
14
15
T
SP
T
WC
—
ns
ms
cycles
Note 1:
Not 100% tested.
2:
The combined T
SP
and V
HYS
specifications are due to new Schmitt Trigger inputs, which provide improved
noise spike suppression. This eliminates the need for a T
I
specification for standard operation.
3:
This parameter is not tested but ensured by characterization. For endurance estimates in a specific
application, please consult the Total Endurance™ Model which can be obtained from Microchip’s web site
at
www.microchip.com.
DS25009C-page 4
2011 Microchip Technology Inc.
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