Data Sheet
PT7C4337
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
Two Time-of-Day Alarms
Oscillator Stop Flag
Operating range: 1.8V to 5.5V
Product Description
The PT7C4337 serial real-time clock is a low-power
clock/calendar with two programmable time-of-day
alarms and 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 either the
24-hour or 12-hour format with AM/PM indicator.
Ordering Information
Part Number
PT7C4337PE
PT7C4337WE
PT7C4337UE
Package
Lead free 8-Pin DIP
Lead free 8-Pin SOIC
Lead free 8-Pin MSOP
Table 1 shows the basic functions of PT7C4337. More
details are shown in section: overview of functions.
Table 1.
Basic functions of PT7C4337
Item
Source
1
Oscillator
Function
Crystal: 32.768kHz
External input
PT7C4337
√
√
√
√
√
√
√
√
2
1, 4.096k, 8.192k, 32.768k
Oscillator enable/disable
Oscillator fail detect
12-hour
24-hour
2
Time
Time display
Century bit
3
4
Alarm interrupt
Programmable square wave output (Hz)
PT0205(02/07)
1
Ver: 1
Data Sheet
PT7C4337
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
Oscillator related bits .............................................................................................................................................................. 7
Square wave frequency selection bits ..................................................................................................................................... 7
Interrupt related bits ................................................................................................................................................................ 8
Time Counter .............................................................................................................................................................................. 9
Days of the week Counter ......................................................................................................................................................... 10
Calendar Counter ...................................................................................................................................................................... 10
Alarm Register .......................................................................................................................................................................... 11
Alarm Function
........................................................................................................................................................................... 12
I
2
C Bus Interface.............................................................................................................................................................................
14
Overview of I
2
C-BUS
.................................................................................................................................................................. 14
System Configuration
................................................................................................................................................................. 14
Starting and Stopping I
2
C Bus Communications
..................................................................................................................... 15
Slave Address
.............................................................................................................................................................................. 17
Maximum Ratings...........................................................................................................................................................................
19
Recommended Operating Conditions
........................................................................................................................................... 19
DC Electrical Characteristics.........................................................................................................................................................
20
AC Electrical Characteristics.........................................................................................................................................................
21
Mechanical Information
................................................................................................................................................................. 22
PT0205(02/07)
2
Ver: 1
Data Sheet
PT7C4337
Real-time Clock Module (I
2
C Bus)
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Pin Assignment
PT7C4337
1
X1
X2
INTA
GND
VCC
8
2
SQW/INTB
7
SCL
SDA
6
3
4
5
Pin Description
Pin no.
1
2
6
5
3
7
8
4
Pin
X1
X2
SCL
SDA
INTA
SQW/INTB
VCC
GND
Type
I
O
I
I/O
O
O
P
P
Description
Oscillator Circuit Input.
Together with X2, 32.768kHz crystal is connected between them.
Or external clock input.
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.
Interrupt Output.
When enabled, INTA is asserted low when the time matches the values set
in the alarm registers. This pin is an open-drain output and requires an external pull up resistor.
Square-Wave/Interrupt Output.
Programmable square-wave or interrupt output signal. It is
an open-drain output and requires an external pull up resistor.
Power.
Ground.
PT0205(02/07)
3
Ver: 1
Data Sheet
PT7C4337
Real-time Clock Module (I
2
C Bus)
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Function Block
Comparator 1
Alarm 1 Register
(Sec, Min, Hour, Day/Date)
PT7C4337
Comparator 2
X1
32.768
kHz
C
D
Alarm 2 Register
(Min, Hour, Day/Date)
OSC
Counter Chain
Time Counter
(Sec,Min,Hour,Day,Date,Month,Year)
X2
C
G
Control Register
Address
Decoder
Address
Register
I /O
Interface
(I
2
C)
Shift Register
SCL
INTA
SQW/INTB
Interrupt Control
Square Wave Output Control
SDA
Recommended Layout for Crystal
PT7C4337
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.
PT0205(02/07)
4
Ver: 1
Data Sheet
PT7C4337
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 2100.
Alarm function
This device has two alarm system (Alarm 1 and Alarm 2) that outputs interrupt signals from INTA or INTB to CPU when the date,
day of the week, hour, minute or second correspond to the setting. Each of them may output interrupt signal separately at a
specified time. The alarm is be selectable between on and off for matching alarm or repeating alarm.
Programmable square wave output
A square wave output enable bit controls square wave output at pin 7. 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 fail detect
When oscillator fail, PT7C4337 OSF bit will be set.
Oscillator enable/disable
Oscillator and time count chain can be enabled or disabled at the same time by /ETIME bit.
PT0205(02/07)
5
Ver: 1
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