Data Sheet
PT7C4372A/4372B
Real-time Clock Module (I
2
C Bus)
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Product Features
• External quartz oscillator 32.000kHz and 32.768kHz
selectable.
• 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)
• Select between 12-hr and 24-hr clock display
• Auto calculation of leap years until 2099
• Built-in high-precision clock precision control logic
• Interrupt generation function (cycle time range: 1
month to 0.5 seconds, includes interrupt flags and
interrupt stop function)
• Alarm functions (Alarm_A/B: Day/Hour/Min)
• 32-kHz clock output (PT7C4372B: FOUT output;
PT7C4372A: /INTB output)
• Oscillation stop detection function (used to determine
presence of internal data)
• Wide clock voltage range: 1.45 V to 6 V
Product Description
PT7C4372A/B are I
2
C bus interface-compliant real-time
clocks that have been adjusted for high precision. In
addition to providing a function for generating six types
of interrupts, a dual alarm function, an oscillation stop
detection function (used to determine presence of valid
internal data at power-on), they includes a digital clock
precision adjustment function that can be used to set
various levels of precision.
Since the internal oscillation circuit is driven at a
constant voltage, 32-kHz clock output is stable and free
of voltage fluctuation effects.
Table 1 shows the diverse functions of the two RTC
circuits. More details are shown in section Overview of
Functions.
Ordering Information
Part Number
PT7C4372AL
PT7C4372BL
PT7C4372AW
PT7C4372BW
Package
8-Pin TSSOP
8-Pin TSSOP
8-Pin SOP
8-Pin SOP
• Wide interface voltage range: 2 V to 6 V
• Low current consumption: 0.5 µA/3.0 V (Typ.)
Note:
Lead free package is available by adding “E” after part
no. For example: PT7C4372ALE is the lead free package of
PT7C4372AL.
Table 1.
Diverse functions of RTC circuits
Item
1
2
3
4
5
6
7
8
Function
Clock
Clock adjustment
Period interrupt
Alarm
Oscillation detect
32-kHz clock output
I
2
C bus interface with CPU
Crystal
PT7C4372A
√
√
Unit
±3.051ppm
for 32.768kHz
crystal;
±3.125ppm
for 32.000kHz
crystal
√
Output from /INTA and /INTB
√
/INTA: Alarm_A; /INTB: Alarm_B
√
√
via /INTB enabled by register
√
√
External, 32.768kHz or 32.000kHz
selectable
PT7C4372B
√
√
Same as PT7C4372A
√
Output from /INTA
√
/INTA: Alarm_A or Alarm_B
√
√
via FOUT enable by register
√
√
Same as PT7C4372A
PT0150(03/06)
1
Ver: 3
Data Sheet
PT7C4372A/4372B
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
Function Description ······················································································································································ 5
Overview of Functions ··········································································································································· 5
Clock function················································································································································· 5
Clock precision adjustment function··············································································································· 5
Periodic interrupt ············································································································································ 5
Alarm function ················································································································································ 5
Oscillation stop detection function, power drop detection function ·······························································5
(voltage monitoring function), and power-on reset detection function
32-kHz clock output········································································································································ 5
Registers ································································································································································· 6
Allocation of Registers ··································································································································· 6
Register 1 ························································································································································ 7
Register 2 ························································································································································ 8
Time Counter ·················································································································································· 9
Days of the Week Counter ······························································································································ 10
Calendar Counter ············································································································································ 10
Time Trimming Register································································································································· 10
Alarm Register ················································································································································ 11
Clock Precision Adjustment Function ···················································································································· 12
Alarm Function······················································································································································· 13
Periodic Interrupt Function····································································································································· 16
Various Detection Function···································································································································· 19
Reading / Writing Data via the I
2
C Bus Interface··································································································· 20
Overview of I
2
C-BUS ····································································································································· 20
System Configuration ····································································································································· 20
Starting and Stopping I2C Bus Communications ··························································································· 21
Data Transfers and Acknowledge Responses during I
2
C-BUS Communication············································ 22
Slave Address·················································································································································· 23
Configuration of Oscillating Circuit and Timing Trimming ·························································································· 26
Specifications ································································································································································· 28
Recommended Operating Conditions····················································································································· 28
Frequency Characteristics······································································································································· 28
DC Electrical Characteristics·································································································································· 29
AC Electrical Characteristics·································································································································· 30
Mechanical Information ················································································································································· 31
L/LE (8-pin TSSOP) ·············································································································································· 31
W/WE (8-pin SOP) ················································································································································· 32
Notes··············································································································································································· 33
PT0150(03/06)
2
Ver: 3
Data Sheet
PT7C4372A/4372B
Real-time Clock Module (I
2
C Bus)
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Pin Assignment
PT7C4372A
1
PT7C4372B
8
1
INTB
SCL
SDA
GND
Vcc
OSCIN
OSCOUT
INTA
FOUT
SCL
SDA
GND
Vcc
OSCIN
OSCOUT
INTA
8
2
7
2
7
3
6
3
6
4
5
4
5
8 pin TSSOP
8 pin SOP
8 pin TSSOP
8 pin SOP
Pin Description
Pin
4372
A
B
1
1
2
3
4
5
6
7
8
2
3
4
5
6
7
8
Pin
Name
/INTB
FOUT
SCL
SDA
GND
Type
O
O
I
I/O
P
O
O
I
P
Description
Interrupt B (Open Drain).
It outputs alarm interrupts and periodic interrupts.
Oscillating Clock Output (CMOS).
It can be disabled by a command from CPU.
Serial Clock Line.
It is for I
2
C communication. Data input and output across SDA pin is
synchronized with this clock. Up to 6V beyond Vcc may be input.
Serial Data Line (Open Drain output).
This line is for transferring I
2
C bus format data.
When input, up to 6V beyond VCC may be used. When output, it is an open drain output
pin.
Ground
Interrupt A (Open Drain).
It outputs alarm interrupts and periodic interrupts.
Oscillator Circuit Output.
Together with OSCIN, an crystal oscillator is connected
between them.
Oscillator Circuit Input.
See OSCOUT pin description.
Power
/INTA
OSCOUT
OSCIN
Vcc
PT0150(03/06)
3
Ver: 3
Data Sheet
PT7C4372A/4372B
Real-time Clock Module (I
2
C Bus)
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Function Block
Comparator_A
FOUT
(PT7C4372B only)
Alarm_A Register
(Week,Min,Hour)
Alarm_B Register
(WEEK,MIN,HOUR)
32kHz Output Control
Comparator_B
OSCIN
C
D
OSC
Divider
Correction
Div
Time Counter
(Sec,Min,Hour,Day,Date,Month,Year)
OSCOUT
C
G
OSC
Detect
Address
Decoder
Address
Register
I /O
Control
SCL
/INTA
(PT7C4372A only)
Interrupt Control
Shift Register
/INTB
SDA
PT0150(03/06)
4
Ver: 3
Data Sheet
PT7C4372A/4372B
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.
Clock precision adjustment function
They have two internal oscillation circuit capacitors, so that an
oscillation circuit may be configured simply by externally
connecting a crystal. Either 32.768kHz or 32.000kHz crystal
may be selected to setting the internal register appropriately.
The clock precision can be adjusted forward or back in units
of ±3.051 ppm (32.768kHz crystal) or ±3.125 ppm
(32.000kHz crystal) and oscillation frequency can be adjusted
in ±189 ppm (32.768kHz crystal) or ±194 ppm (32.000kHz
crystal).
This function can be used to implement a higher-precision
clock function, such as by:
•
Enabling higher clock precision throughout the year by
taking seasonal clock precision adjustments into account
in advance, or
•
Enabling correction of temperature-related clock
precision variation in systems that include a temperature
detecting function.
Periodic interrupt
•
PT7C4372A
Periodic interrupts can be output via the /INTA and /INTB
pins.
Select among five Periodic frequency settings: 2 Hz (every 0.5
seconds), 1 Hz (every second), 1/60 Hz (every minute),
1/3600Hz (every hour), or monthly.
Select among two output waveforms for periodic interrupts:
ordinary pulse waveform (2 Hz or 1 Hz) or waveforms (every
second, minute, hour, or month) for CPU-level interrupts that
can support CPU interrupts.
A polling function is also provided to enable monitoring of
pin states via registers.
•
Alarm function
•
PT7C4372A
This module is has two alarm system (Alarm_A and Alarm_B)
that outputs interrupt signals from /INTA or /INTB to CPU
when the day of the week, hour or minute corresponds to the
setting. Each of them may output interrupt signal separately at
a specified time. The alarm may be selectable between on and
off for each day of the week, thus allowing outputting alarm
everyday or on a specific day of the week.
The Alarm_A is output from the /INTA pin while the
Alarm_B is output from either the /INTA or the /INTB pins.
Polling is possible separately for each alarm function.
•
PT7C4372B
This module is equipped with two alarm functions (Alarm_A
and Alarm_B) that output interrupt signals from /INTA to the
host when to day of the week, hour or minute corresponds to
the setting. The alarm may be selectable between on and off
for each day of the week, thus allowing outputting alarm
everyday or on a specific day of the week.
Polling is possible separately for each alarm function.
Oscillation stop detection function, power drop detection
function (voltage monitoring function), and power-on reset
detection function
PT7C4372A/B have only oscillation stop detection function.
The oscillation stop detection function uses registers to record
if clock data is valid or invalid. This function may be used to
determine if the PT7C4372A/B supply power has been booted
from 0V and if it has been backed up.
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 of 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.
32-kHz clock output
The 32.768 kHz clock (32.768kHz crystal) or 32.000kHz
clock (32.000kHz crystal) can be output via the /INTB (only
PT7C4372A) or FOUT (only PT7C4372B) pin by setting
corresponding register.
Note:
The precision of this 32.768 kHz clock output via the
FOUT pin can not be adjusted (even when using the clock
precision adjustment function).
PT7C4372B
Periodic interrupts can be output via the /INTA pin.
Select among five Periodic frequency settings: 2 Hz (every 0.5
seconds), 1 Hz (every second), 1/60 Hz (every minute),
1/3600Hz (every hour), or monthly.
Select among two output waveforms for periodic interrupts:
ordinary pulse waveform (2 Hz or 1 Hz) or waveforms (every
second, minute, hour, or month) for CPU-level interrupts that
can support CPU interrupts.
A polling function is also provided to enable monitoring of
pin states via registers.
5
PT0150(03/06)
Ver: 3
