Datasheet
Real-Time Clock (RTC) series
I C BUS Serial Interface RTC
with High-precision Oscillation Adjustment
BU9873
Outline
The BU9873 is a CMOS real-time clock, which has a
built-in interrupt generation function. This product is
2
connected to the CPU via I C interface, and configured to
perform serial transmission of time and calendar data to
the CPU. A high-precision oscillation adjustment circuit is
also integrated, which is capable of adjusting time counts
with digital method, and correcting deviations in the
oscillation frequency of the crystal oscillator.
2
Important Characteristics
■
■
■
■
■
■
Time Keeping Voltage
Time Keeping Current 1
(V
DD
=3V, Ta=+25°C)
Time Keeping Current 2
(V
DD
=3V, Ta=-40°C to +85°C)
Power Supply Voltage
Access Frequency 1
(V
DD
=1.8V to 2.5V)
Access Frequency 2
(V
DD
=2.5V to 5.5V)
1.45V to 5.5V
0.4µA (Typ)
1.0µA (Max)
1.8V to 5.5V
100kHz (Max)
400kHz (Max)
Features
■
■
■
■
Connected to the CPU via I C Interface
Time (Hour
½
Minute
½
Second, Selectable 12-Hour
and 24-Hour Mode Setting)
Calendar (Year½Month½Day½Week)
Periodic Interrupt Function
(Output from INTRB, Ranging from 1 Second to 1
Month)
Alarm Interrupt Function
(Day-of-Week
½
Hour
½
Minute in Setting Format,
Output from INTRB)
Oscillation Halt Sensing Function
32.768 kHz Clock Output
(Output from 32KOUT with Control Pin)
±30 Second Adjustment Function
Automatic Leap Year Recognition up to the Year
2099
Built-in Oscillation Stabilizing Capacitors (C
G
, C
D
)
High-Precision Oscillation Adjustment Circuit
2
Package
W (Typ) x D (Typ) x H (Max)
SOP8
5.00mm x 6.20mm x 1.71mm
MSOP8
2.90mm x 4.00mm x 0.90mm
■
■
■
■
■
■
■
SOP- J8
4.90mm x 6.00mm x 1.65mm
VSON008X2030
2.00mm x 3.00mm x 0.60mm
TSSOP-B8
3.00mm x 6.40mm x 1.20mm
○Product
structure: Silicon monolithic integrated circuit
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© 2013 ROHM Co., Ltd. All rights reserved.
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○This
product has no designed protection against radioactive rays
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BU9873
Typical Application Circuit
Datasheet
Figure 1. Typical application circuit (with primary battery)
Figure 2. Typical application circuit (with secondary battery)
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BU9873
Pin Configuration
(TOP VIEW)
VDD
8
OSCIN
7
OSCOUT
6
:SOP8
:SOP-J8
:TSSOP-B8
:MSOP8
:VSON008X2030
INTRB
5
Datasheet
BU9873F
BU9873FJ
BU9873FVT
BU9873FVM
BU9873NUX
1
32KOUT
2
SCL
3
SDA
4
VSS
Figure 3. Pin configuration
Pin Description
Pin No.
1
2
3
4
5
6
7
8
Symbol
32KOUT
SCL
SDA
VSS
INTRB
OSCOUT
OSCIN
VDD
Input/Output
Output
Function
The 32KOUT pin is used to output 32.768 kHz clock pulses, which is
controlled by an internal register. This pin is enabled during power-on
from 0V, and is CMOS push-pull output.
The SCL pin is used to input clock pulses synchronizing the input/output
Input
data from SDA pin.
The SDA pin is used to input and output data for writing and reading,
Input/Output which is synchronized with SCL pin. This pin is N-channel open drain
output.
-
Output
-
-
-
The VSS pin is grounded.
The INTRB pin is used to output periodic interrupt, or alarm interrupt
(Alarm_A, Alarm_B) to the CPU. This pin is disabled during power-on
from 0V, and is also N-channel open drain output.
The OSCIN and OSCOUT pins are used to connect the 32.768 kHz
crystal oscillator (Beside the crystal, all other oscillation circuit
components is already integrated in this IC).
The VDD pin is connected to the power supply.
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BU9873
Block Diagram
Datasheet
32KOUT
1
32KOUT
CONTROL
8
VDD
I/O
TIME COUNTER
SEC
MIN
HOUR
WEEK
DAY
MONTH
YEAR
OSC
DETECT
OSC
SCL
2
FILTER
CONTROL
7
OCSIN
DIV
SDA
3
FILTER
SDA
CONTROL
ALARM_A
COMP_A
6
OSCOUT
VSS
4
ALARM_B
COMP_B
INTRB
CONTROL
5
INTRB
Figure 4. Block diagram
Absolute Maximum Ratings
Item
Supply Voltage
Symbol
V
DD
Rating
－0.3
to
＋6.5
0.45 (SOP8)
0.45 (SOP-J8)
Power Dissipation
Pd
0.33 (TSSOP-B8)
0.31 (MSOP8)
0.30 (VSON008X2030)
Storage
Temperature
Operating
Temperature
Terminal Voltage
Tstd
Topt
―
－55
to +125
－40
to +85
-0.3 to V
DD
+0.3
°C
°C
V
The Max value of Terminal Voltage is not over 6.5V.
When the pulse width is 50ns or less, the Min value of
Terminal Voltage is not lower than -0.8V.
Unit
V
Remark
When using above Ta=25, decreased by 4.5mW/°C.
When using above Ta=25, decreased by 4.5mW/°C.
W
When using above Ta=25, decreased by 3.3mW/°C.
When using above Ta=25, decreased by 3.1mW/°C.
When using above Ta=25, decreased by 3.0mW/°C.
Caution: Operating the IC over the absolute maximum ratings may damage the IC. In addition, it is impossible to predict all destructive situations such as
short-circuit modes, open circuit modes, etc. Therefore, it is important to consider circuit protection measures, like adding a fuse, in case the IC is operated in a
special mode exceeding the absolute maximum ratings
Recommended Operating Conditions
Item
Supply Voltage
Timekeeping
(Note 1)
Voltage
Input Voltage
Symbol
V
DD
V
CLK
V
IN
Rating
1.8 to 5.5
1.45 to 5.5
0 to V
DD
Unit
V
V
V
(Note1) For minimum time keeping voltage, C
GOUT
= C
DOUT
= 0 pF; Quartz crystal unit: C
L
(load capacitor) = 6 pF to 12.5 pF, Maximum value of R
1
(equivalent
series resistance) = 80 KΩ.
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BU9873
DC Characteristics
Item
“H” Input Voltage
“L” Input Voltage
“H” Output Current
Symbol
V
IH
V
IL
I
OH
I
OL1
“L” Output Current
I
OL2
Input Leakage Current
Output Off State Leakage
Current
I
ILK
I
OZ
SDA
SCL
SDA, INTRB,
32KOUT
6
-1
-1
－
－
－
－
1
1
mA
μA
μA
Pin Name
SCL, SDA
SCL, SDA
32KOUT
INTRB, 32KOUT
Spec
Min
0.7V
DD
-0.3
－
1
Typ
－
－
－
－
Max
V
DD
+0.3
0.3V
DD
-0.5
－
Unit
V
V
mA
mA
Datasheet
Conditions
V
OH
=V
DD
-0.5V
V
OL1
=0.4V
V
OL2
=0.4V
V
IN
=5.5V or V
SS
, V
DD
=5.5V
V
OUT
=5.5V or V
SS
,
V
DD
=5.5V
V
DD
=3V,
Topt=25°C,
SCL, SDA=3V,
C
GOUT
=C
DOUT
=0pF,
(Note1)
Output=Open
V
DD
=3V,
Topt=-40°C to +85°C,
SCL, SDA=3V,
C
GOUT
=C
DOUT
=0pF,
(Note1)
Output=Open
V
DD
=5.5V,
Topt=-40°C to +85°C,
SCL, SDA=5.5V,
C
GOUT
=C
DOUT
=0pF,
Output=Open
(Note1)
I
DD1
VDD
－
0.4
0.6
μA
Standby Current
(time keeping current)
I
DD2
VDD
－
－
1.0
μA
I
DD3
VDD
－
－
1.35
μA
Internal Oscillation
Capacitance 1
Internal Oscillation
Capacitance 2
C
G
C
D
OSCIN
OSCOUT
－
－
10
10
－
－
pF
pF
Unless otherwise specified: Vss=0V, V
DD
=3V, Topt=−40°C to +85°C, Oscillation frequency=32.768 kHz
(load capacitance C
L
=6pF, equivalent series resistance R
1
=20kΩ)
(Note 1) In this mode, 32KOUT is disabled and no clock is output from this pin.
For time keeping current when outputting 32-kHz pulse from 32KOUT pin (this pin without loading), please refer to “P.7 Typical Performance Curves”.
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