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PT7C4311
Real-time Clock Module (I
2
C Bus)
Features
Support I
2
C-Bus (High speed mode 400kHz)
Includes time (Hour/Minute/Second) and calendar
(Century/Year/Month/Date/Day) counter functions
Year 2000 compliant
Automatic switch-over and deselect circuitry
Time keeping voltage: 1.2V to 5.5V
Software clock calibration
56 bytes of general purpose RAM
Ultra-low battery supply current of 0.3A
Low operating current of 70A
Battery or super cap back-up
Operating temperature: -40° to 85°
C
C
Automatic leap year compensation
Special software programmable output
Description
The PT7C4311 serial real-time clock is a low-power
clock/calendar with a programmable square-wave output.
Address and data are transferred serially via a 2-wire
bidirectional bus. The clock/calendar provides seconds,
minutes, hours, day, date, month, and year information.
The date at the end of the month is automatically
adjusted for months with fewer than 31 days, including
corrections for leap year. The clock operates in the 24-
hour format indicator.
Table 1 shows the basic functions of PT7C4311. More
details are shown in section: overview of functions.
Pin Configuration
Pin Description
Description
Oscillator Circuit Input.
Together with X1, 32.768kHz crystal is connected between them. Or
1
X1
I
external clock input.
2
X2
O
Oscillator Circuit Output.
Together with X1, 32.768kHz crystal is connected between them.
Battery Supply Voltage.
When V
CC
>V
SO
1
, VCC will power the IC. While V
CC
<V
SO
1
, VBAT
3
VBAT
P
will power the IC.
4
GND
P
Ground.
5
SDA
I/O
Serial Data Input/Output.
SDA is the input/output pin for the 2-wire serial interface. The SDA
pin is open-drain output and requires an external pull-up resistor.
6
SCL
I
Serial Clock Input.
SCL is used to synchronize data movement on the I
2
C serial interface.
Frequency Test / Output Driver.
Open drain. 512Hz output when Frequency Test is selected.
7
FT/OUT
O
Output DC level by register selection. Frequency Test is prior.
Supply Voltage.
When V
CC
>V
SO
1
, VCC will power the IC. While V
CC
<V
SO
1
, VBAT will power
8
VCC
P
the IC.
Note:
1. V
SO
: Battery Back-up Switchover Voltage
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Pin no.
Pin
Type
PT7C4311
Real-time Clock Module (I
2
C Bus)
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Table 1.
Basic functions of PT7C4311
Item
1
Oscillator
Function
PT7C4311
-
-
-
512Hz
568
Source: Crystal: 32.768kHz
Oscillator enable/disable
Oscillator fail detect
Time display
2
Time
Century bit
12-hour
24-hour
3
4
5
6
7
8
Time count chain enable/disable
Programmable square wave output (Hz)
Programmable high/low level output
Communication
RAM
Battery backup
Clock calibration
2-wire I
2
C bus
Function Block
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PT7C4311
Real-time Clock Module (I
2
C Bus)
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Maximum Ratings
Storage Temperature............................................................................................................... -55oCto +125oC
Ambient Temperature with Power Applied...................................................................... -40oCto +85oC
Supply Voltage to Ground Potential (Vcc to GND) ...................................................... -0.3V to +7.0V
DC Input (All Other Inputs except Vcc & GND) ...........................................................-0.3V to +7.0V
DC Output Voltage .................................................................................................................-0.3V to +7.0V
Power Dissipation.................................................................................................................... 250mW
Output Current.......................................................................................................................... 20mA
Note:
Stresses greater than those listed under MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions above those indicated in the operational sections of
this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Recommended Operating Conditions
Symbol
Description
Timing data and RAM data maintaining voltage
Timing data writing voltage
V
CC
Timing data reading voltage
RAM data writing voltage
RAM data reading voltage
V
IH
V
IL
T
A
Input high level
Input low level
Operating temperature
Min
1.2
1.5
1.5
3.0
1.5
0.7 V
CC
-0.3
-40
Type
-
-
-
-
-
-
-
-
Max
5.5
5.5
5.5
5.5
5.5
V
CC
+0.3
0.3 V
CC
85
º
C
V
Unit
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PT7C4311
Real-time Clock Module (I
2
C Bus)
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DC Electrical Characteristics
(Unless otherwise specified, V
CC
= 1.5 ~ 5.5 V, T
A
= -40 ° to +85 °
C
C.)
Sym.
Description
Timing data and RAM data
maintaining voltage
Timing data writing voltage
Timing data reading voltage
RAM data writing voltage
RAM data reading voltage
Supply voltage
Battery Back-up Switchover
Voltage
3,4
Current consumption
Standby current
Current consumption
Low-level input voltage
High-level input voltage
Low-level output voltage
Pull-up Supply voltage
(Open drain)
Input leakage current
Output current when OFF
Pin
VCC
VCC
VCC
VCC
VCC
VBAT
-
VCC
VCC
VBAT
-
-
SDA
FT/
OUT
SCL
SDA
-
-
-
-
-
-
Switch freq. = 400kHz
SDA, SCL = V
CC
– 0.3V
OSC on, V
CC
= 0V, V
BAT
= 3V,
T
A
=25°
C
-
-
I
OL
= 3mA
-
0<V
IN
<V
CC
0<V
OUT
<V
CC
Condition
Min
1.2
1.5
1.5
3.0
1.5
2.0
V
BAT
-
0.80
-
-
-
-0.3
0.7V
CC
-
-
-
-
Typ
-
-
-
-
-
3
V
BAT
-
0.50
70
25
300
-
-
-
-
-
-
Max
5.5
5.5
5.5
5.5
5.5
3.5
6
V
BAT
-
0.30
5
150
80
800
0.3V
CC
V
CC
+0.5
0.4
5.5
1
1
V
Unit
V
CC
V
BAT1
V
SO2
I
CC
I
ST
I
BAT
V
IL
V
IH
V
V
A
A
nA
V
V
OL
I
IL
I
OZ
V
A
A
Note:
1. After switchover (V
SO
), V
BAT
(min) can be 2.0V for crystal with R
S
=40k.
2. Switch-over and deselect point.
3. Valid for Ambient Operating Temperature: T
A
= -40 to 85° V
CC
= 2.0 to 5.5V (except where noted). VCC fall time should
C;
not exceed 5 mV/μs.
4. All voltages referenced to GND.
5. In 3.3V application, if initial battery voltage is ≥ 3.4V, it may be necessary to reduce battery voltage (i.e., through wave
soldering the battery) in order to avoid inadvertent switchover/reselection for VCC – 10% operation.
6. For rechargeable backup, V
BAT
(max) may be considered to be V
CC
.
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Real-time Clock Module (I
2
C Bus)
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AC Electrical Characteristics
Sym
V
HM
V
HL
Description
Rising and falling threshold voltage high
Rising and falling threshold voltage low
Value
0.8 V
CC
0.2 V
CC
Unit
V
V
Signal
V
HM
V
LM
t
f
Over the operating range
Symbol
f
SCL
t
SU;STA
t
HD;STA
t
SU;DAT
t
HD;DAT
t
SU;STO
t
BUF
t
LOW
t
HIGH
t
r
t
f
C
B
SCL clock frequency
START condition set-up time
START condition hold time
Data set-up time (RTC read/write)
Data hold time (RTC read/write)
STOP condition setup time
Bus idle time between a START and STOP condition
When SCL = "L"
When SCL = "H"
Rise time for SCL and SDA
Fall time for SCL and SDA
Capacitance load for each bus line
Item
STAND Mode (I
2
C)
Min.
-
4.7
4.0
250
0
4.0
4.7
4.7
4.0
-
-
0
Max.
100
-
-
-
-
-
-
-
-
1.0
0.3
400
FAST Mode (I
2
C)
Min.
-
0.6
0.6
100
0
0.6
1.3
1.3
0.6
20+0.1C
B
20+0.1C
B
0
Max.
400
-
-
-
0.9
-
-
-
-
0.3
0.3
400
Unit
kHz
s
s
ns
us
s
s
s
s
s
s
pF
t
r
Timing Diagram
S
SCL
t
LOW
f
SCL
t
HIGH
Sr
t
HD;STA
t
SP
P
t
SU;STA
t
BUF
SDA
t
HD;STA
t
SU;DAT
t
HD;DAT
t
SU;STA
t
SU;STO
t
HD;STA
S
Sr
Start condition
Restart condition
P
Stop condition
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嵌入式系统
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