Contents
Features..................................................................... 1
Applications ............................................................... 1
Block Diagram ........................................................... 1
Pin Assignment .......................................................... 2
Description of Pins ..................................................... 3
Description of Operation............................................. 4
1. Serial interface ............................................ 4
2. Command configuration................................ 8
3. Initialization .................................................. 12
4. Processing of none-existent data
and end-of month ......................................... 14
5. Interrupt ........................................................ 14
6. Power voltage detecting circuits.................... 16
7. Example of software treatment ..................... 17
Sample of Applied Circuits ......................................... 18
Order Specification .................................................... 19
Adjustment of Oscillating Frequency .......................... 19
1. Configuration of the oscillating circuit............ 19
2. Measurement of oscillating frequencies ........ 20
3. Adjustment fo oscillating frequencies ............ 21
Absolute Maximum Ratings........................................ 22
Recommended Operating Conditions......................... 22
Oscillation Characteristics .......................................... 22
DC Electrical Charasteristics ...................................... 23
AC Electrical Charasteristics ...................................... 24
Sample of Characteristic (Reference Values) ............. 25
Dimensional Outline Diagram (Unit:mm) .................... 27
Rev.1.2
REAL-TIME CLOCK
S-3531A
S-3531A is a CMOS real-time clock IC supporting an I C-BUS, which is
designed to transfer or set each data of a clock and calender as
requested by a CPU. It provides connection with a CPU via two wires and
has two systems of interrupt/alarm and clock output features, allowing the
alleviation of software treatment on the side of a host.
It also works on lower power with the oscillating circuit operated at a
constant voltage. The shipping form is either a die or an 8-pin SSOP ultra
compact package.
2
!
Features
•
Low power consumption
: 0.7
µA
typ. (V
DD
=3.0 V)
•
Wide area of operating voltage : 1.7 to 5.5 V
•
BCD input/output of year, month, day,
day of a week, hour, minute and second
2
•
CPU interface via two wires (I C- BUS)
•
Auto calender till the year of 2,099
(automatic leap year arithmetic feature included)
•
Built-in power voltage detecting circuit
•
Built-in constant voltage circuit
•
Built-in flag generating circuit on power on/off
•
Built-in alarm interrupter
•
Steady-state interrupt frequency/duty setting feature
•
Built-in 32 KHz crystal oscillating circuit (Internal Cd, External Cg)
•
Die or 8-pin SSOP package (pin pitch: 0.65 mm)
2
(*) I C-BUS is a trademark of PHILLIPS ELECTRONICS N.V.
!
Applications
•
•
•
•
•
Cellular phone
PHS
A variety of pagers
TV set and VCR
Camera
!
Block Diagram
Clock
generating
circuit
XIN
XOUT
Oscillating
circuit
Timing
generatio
n
INT1 Register
Compa-
rator 1
INT1
F
32K
Second
Minute
Hour
Day of
week
Day
Month
Year
V
DD
Power
voltage
detecting
circuit
Constant
voltage
circuit
Status register
V
SS
Shift register
I C-BUS
Interface
2
SDA
SCL
Figure 1 Block diagram
Seiko Instruments Inc.
1
REAL-TIME CLOCK
S-3531A
n
Pin Assignment
(1) Package : S-3531AEFS
8-pin SSOP
Top view
INT1
XIN
XOUT
VSS
1
2
3
4
8
7
6
5
VDD
SDA
SCL
F
32K
Figure 2 Pin assignment
(2) Die : S-3531AECA
Y
INT1
XIN
0
XOUT
VDD
SDA
X
SCL
S-3531A
VSS
F
32K
(*1) Die size :
2.10
×
1.60 mm
Sizes shown are for design purposes only.
The corners of the die shrink by approximately 30
µm
after dicing.
(*2) Pad size : 100
×
100
µm
Pad Coordinates
Symbol
INT1
XIN
XOUT
VSS
X-
Y-
Coordinate Coordinate
−890
−890
−890
−890
641
351
−114
−641
Symbol
VDD
SDA
SCL
F
32K
X-
Y-
Coordinate Coordinate
890
890
890
890
641
356
−240
−641
Figure 2-2 Pad assignment
2
Seiko Instruments Inc.
REAL-TIME CLOCK
S-3531A
n
Description of Pins
Table 1 Description of pins
Pin No.
1
Symbol
INT1
Description
Configuration
N-channel open drain
Alarm interrupt 1 output pin.
Depending on the mode set by the INT1
output (No protective diode
register and status register, it outputs low or on the side of VDD)
Clock when time is reached. It is disabled by
rewriting the status register.
Crystal oscillator connect pin (32,768 Hz)
(Internal Cd, External Cg)
Negative power supply pin (GND)
N-channel open drain
32,768 Hz clock output pin.
This clock is always being output and cannot output (No protective diode
be controlled by command.
on the side of VDD)
CMOS input (No protective
Serial clock input pin.
Follow the specification with great care to the diode on the side of VDD)
rising/falling time of the SCL signal because
the signal is treated at its rising/falling edge.
N-channel open drain
Serial data input/output pin.
output (No protective diode
This pin is usually pulled up to VDD via a
on the side of VDD)
resistor, and connected to other open-drain or
CMOS input
open-collector output devices in wired OR
configuration.
Positive power supply pin.
2
3
4
5
XIN
XOUT
VSS
F
32K
6
SCL
7
SDA
8
VDD
Seiko Instruments Inc.
3
REAL-TIME CLOCK
S-3531A
n
Description of Operation
1. Serial interface
S-3531A receives various commands through the I
2
C-BUS-based serial interface to read/write data.
The method of I
2
C-BUS-based transfer is described here.
1-1. Start condition
Changing the SDA line from “H” to “L” when the SCL line is “H” activates the start condition.
All the operations begin at the start condition.
1-2. Stop condition
Changing the SDA line from “L” to “H” when the SCL line is “H” activates the stop condition.
During a read sequence, any read operation is stopped and a device enters its stand-by mode
when a stop condition is received.
t
SU.STA
t
HD.STA
t
SU.STO
SCL
SDA
Start condition
Stop condition
Figure 3 Start/Stop condition
1-3. Data transfer
When the SDA line is changed while the SCL line is on “L”, data transfer is performed.
When the SDA line is changed while the SCL line is on “H”, a start or stop condition is recognized.
t
SU.DAT
t
HD.DAT
SCL
SDA
Figure 4 Data transfer timing
4
Seiko Instruments Inc.
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