DS1340 Maxim, DS1340 Datasheet - Page 6

• Manufacturer Part Number: DS1340
• Description: The DS1340 is a real-time clock (RTC)/calendar that is pin compatible and functionally equivalent to the ST M41T00, including the software clock calibration
• Manufacturer: Maxim

I
The DS1340 is a low-power clock/calendar with a trickle
charger. Address and data are transferred serially
through a I
vides 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 DS1340
has a built-in power-sense circuit that detects power fail-
ures and automatically switches to the backup supply.
The power-control function is provided by a precise,
temperature-compensated voltage reference and a
comparator circuit that monitors the V
device is fully accessible and data can be written and
read when V
falls below V
6
2
—
8
1
2
3
4
5
6
7
8
_______________________________________________________________________________________
C RTC with Trickle Charger
PIN
4–13
16
14
15
16
—
—
1
2
3
2
C bidirectional bus. The clock/calendar pro-
CC
PF
V
FT/OUT
NAME
BACKUP
GND
, the internal clock registers are blocked
SDA
N.C.
SCL
V
is greater than V
X1
X2
CC
Detailed Description
Connections for a Standard 32.768kHz Quartz Crystal. The internal oscillator circuitry is designed for
operation with a crystal having a specified load capacitance (C
oscillator and can optionally be connected to an external 32.768kHz oscillator. The output of the
internal oscillator, X2, is left unconnected if an external oscillator is connected to X1.
Connection for a Secondary Power Supply. For the 1.8V and 3V devices, V
between 1.3V and 3.7V for proper operation. Diodes placed in series between the supply and the input
pin may result in improper operation. V
This pin can be connected to a primary cell such as a lithium coin cell. Additionally, this pin can be
connected to a rechargeable cell or a super cap when used with the trickle-charge feature. UL recognized to
ensure against reverse charging when used with a lithium battery (www.maxim-ic.com/qa/info/ul).
Ground
Serial Data Input/Output. SDA is the data input/output for the I
drain and requires an external pullup resistor.
Serial Clock Input. SCL is the clock input for the I
movement on the serial interface.
Frequency Test/Output. This pin is used to output either a 512Hz signal or the value of the OUT bit.
When the FT bit is logic 1, the FT/OUT pin toggles at a 512Hz rate. When the FT bit is logic 0, the
FT/OUT pin reflects the value of the OUT bit. This open-drain pin requires an external pullup resistor,
and operates with either V
the voltage on V
Primary Power Supply. When voltage is applied within normal limits, the device is fully accessible and
data can be written and read. When a backup supply is connected to the device and V
reads and writes are inhibited. However, the timekeeping function continues unaffected by the lower
input voltage.
No Connection. Must be connected to ground.
PF
Power Control
. However, when V
CC
. If not used, this pin can be left unconnected.
CC
level. The
CC
or V
BACKUP
CC
BACKUP
applied. The pullup voltage can be up to 5.5V, regardless of
from any access. If V
device power is switched from V
V
the device power is switched from V
Table 1. Power Control
CC
SUPPLY CONDITION
FUNCTION
can be as high as 5.5V on the 3.3V device.
drops below V
V
V
V
V
CC
CC
CC
CC
2
V
V
V
V
C interface and is used to synchronize data
CC
CC
CC
CC
< V
> V
< V
> V
< V
< V
> V
> V
BACKUP
BACKUP
BACKUP
BACKUP
PF
PF
PF
PF
,
,
,
,
2
C serial interface. The SDA pin is open
L
PF
) of 12.5pF. X1 is the input to the
. If V
PF
READ/WRITE
PF
is less than V
ACCESS
BACKUP
Yes
Yes
is greater than V
No
No
Pin Description
CC
must be held
to V
CC
CC
is below V
BACKUP
BACKUP
POWERED
to V
V
V
V
V
BY
BACKUP
BAT
BACKUP
CC
CC
CC
PF
when
, the
,
,