Preliminary Data Sheet
PT7C4307
Real-time Clock Module (I
2
C Bus)
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Product Features
•
•
•
Using external 32.768kHz quartz crystal
Supports I
2
C-Bus's high speed mode (400 kHz)
Includes time (Hour/Minute/Second) and calendar
(Year/Month/Date/Day) counter functions (BCD
code)
•
•
•
•
Programmable square wave output signal
56-byte, battery-backed, nonvolatile (NV) RAM for
data storage
Automatic power-fail detect and switch circuitry of
battery backup
Consumes less than 500nA in battery backup mode
with oscillator running
Product Description
The PT7C4307 serial real-time clock is a low-power
clock/calendar with a programmable square-wave output
and 56 bytes of nonvolatile RAM.
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 either the
24-hour or 12-hour format with AM/PM indicator.
The PT7C4307 has a built-in power sense circuit that
detects power failures and automatically switches to the
Ordering Information
Part Number
PT7C4307P
PT7C4307W
Package
8-Pin DIP
8-Pin SOIC
battery supply.
Table 1 shows the basic functions of PT7C4307. More
details are shown in section: overview of functions.
Note:
Lead free package is available by adding “E” after each
part number. For example: PT7C4307PE.
Table 1.
Basic functions of PT7C4307
Item
Function
Source: Crystal: 32.768kHz
1
Oscillator
Oscillator enable/disable
Oscillator fail detect
Time display
Century bit
3
4
5
6
Alarm interrupt
Programmable square wave output (Hz)
RAM
Battery backup
12-hour
24-hour
PT7C4307
√
√
-
√
√
-
-
1, 4.096k, 8.192k, 32.768k
56×8
√
2
Time
PT0206(02/05)
1
Ver: 0
Preliminary Data Sheet
PT7C4307
Real-time Clock Module (I
2
C Bus)
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Contents
Product Features
............................................................................................................................................................................... 1
Product Description
.......................................................................................................................................................................... 1
Pin Assignment..................................................................................................................................................................................
3
Pin Description
.................................................................................................................................................................................. 3
Function Block
.................................................................................................................................................................................. 4
Recommended Layout for Crystal
.................................................................................................................................................. 4
Crystal Specifications
....................................................................................................................................................................... 4
Function Description.........................................................................................................................................................................
5
Overview of Functions
.................................................................................................................................................................. 5
Registers.........................................................................................................................................................................................
6
Control and status register........................................................................................................................................................... 7
Time Counter .............................................................................................................................................................................. 8
Days of the week Counter ........................................................................................................................................................... 9
Calendar Counter ........................................................................................................................................................................ 9
I
2
C Bus Interface.............................................................................................................................................................................
10
Overview of I
2
C-BUS
.................................................................................................................................................................. 10
System Configuration
................................................................................................................................................................. 10
Starting and Stopping I
2
C Bus Communications
..................................................................................................................... 11
Slave Address
.............................................................................................................................................................................. 13
Maximum Ratings...........................................................................................................................................................................
15
Recommended Operating Conditions
........................................................................................................................................... 15
DC Electrical Characteristics.........................................................................................................................................................
16
AC Electrical Characteristics.........................................................................................................................................................
17
Mechanical Information
................................................................................................................................................................. 18
PT0206(02/05)
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Preliminary Data Sheet
PT7C4307
Real-time Clock Module (I
2
C Bus)
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Pin Assignment
PT7C4307
1
X1
VCC
8
2
X2
VBAT
SQW/OUT
SCL
7
3
6
4
GND
SDA
5
DIP-8
SOIC-8
Pin Description
Pin no.
1
Pin
X1
Type
I
Description
Oscillator Circuit Input.
Together with X2, 32.768kHz crystal is connected between them.
Oscillator Circuit Output.
Together with X1, 32.768kHz crystal is connected between them.
When 32.768kHz external input, X2 must be float.
Serial Clock Input.
SCL is used to synchronize data movement on the I
2
C serial interface.
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.
Square Wave/Output Driver.
Open drain. Four frequencies selectable: 32.768k, 8.192k,
4.096k, 1Hz when SQWE bit is set to 1.
Power.
Primary power for PT7C4307.
+3V Battery Power.
Ground.
2
6
5
X2
SCL
SDA
O
I
I/O
7
SQW/OUT
O
8
3
4
VCC
VBAT
GND
P
P
P
PT0206(02/05)
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Preliminary Data Sheet
PT7C4307
Real-time Clock Module (I
2
C Bus)
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Function Block
PT7C4307
X1
32.768
kHz
C
D
OSC
Counter
Chain
Time Counter
(Sec,Min,Hour,Day,Date,Month,Year)
56 x 8
RAM
X2
SQW/OUT
C
G
Control Register
Address
Decoder
Address
Register
I /O
Interface
(I
2
C)
SCL
VCC
VBAT
Power Manager
Shift Registers
SDA
Recommended Layout for Crystal
PT7C4307
X1
32.768kHz
Crystal
X2
Local Ground plane
Layer 2
Guard Ring
(connect to gound)
Crystal Specifications
Parameter
Nominal Frequency
Series Resistance
Load Capacitance
Symbol
f
O
ESR
C
L
Min
Typ
32.768
12.5
Max
45
Unit
kHz
kΩ
pF
The crystal, traces and crystal input pins should be isolated from RF generating signals.
PT0206(02/05)
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Ver: 0
Preliminary Data Sheet
PT7C4307
Real-time Clock Module (I
2
C Bus)
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Function Description
Overview of Functions
Clock function
CPU can read or write data including the year (last two digits), month, date, day, hour, minute, and second. Any (two-digit) year
that is a multiple of 4 is treated as a leap year and calculated automatically as such until the year 2099.
Programmable square wave output
A square wave output enable bit controls square wave output at pin 7. 4 frequencies are selectable: 1, 4.096k, 8.192k, 32.768k Hz.
Interface with CPU
Data is read and written via the I
2
C bus interface using two signal lines: SCL (clock) and SDA (data).
Since the output of the I/O pin SDA is open drain, a pull-up resistor should be used on the circuit board if the CPU output I/O is
also open drain.
The SCL's maximum clock frequency is 400 kHz, which supports the I
2
C bus's high-speed mode.
Oscillator enable/disable
Oscillator can be enabled or disabled by /EOSC bit. But time count chain does not shut down when the bit is logic 1.
RAM
56×8 nonvolatile RAM are available for customer use.
PT0206(02/05)
5
Ver: 0
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