DS1339 Maxim, DS1339 Datasheet - Page 9

• Manufacturer Part Number: DS1339
• Description: The DS1339 serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day alarms and a programmable square-wave output
• Manufacturer: Maxim

DETAILED DESCRIPTION
The DS1339 serial real-time clock (RTC) is a low-power clock/date device with two programmable time-of-day
alarms and a programmable square-wave output. Address and data are transferred serially through an I
The clock/date 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. The DS1339 has a built-in power-
sense circuit that detects power failures and automatically switches to the backup supply, maintaining time, date,
and alarm operation.
OPERATION
The DS1339 operates as a slave device on the serial bus. Access is obtained by implementing a START condition
and providing a device identification code followed by data. Subsequent registers can be accessed sequentially
until a STOP condition is executed. The device is fully accessible and data can be written and read when V
greater than V
V
greater than V
registers are maintained from the V
Figure 3
POWER CONTROL
The power-control function is provided by a precise, temperature-compensated voltage reference and a
comparator circuit that monitors the V
when V
access. If V
V
registers are maintained from the V
above V
time and date registers are reset to 01/01/00 01 00:00:00 (MM/DD/YY DOW HH:MM:SS).
Table 1. Power Control
OSCILLATOR CIRCUIT
The DS1339 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or
capacitors to operate.
functional schematic of the oscillator circuit. The startup time is usually less than 1 second when using a crystal
with the specified characteristics.
V
V
V
V
PF
PF
SUPPLY CONDITION
CC
CC
CC
CC
is greater than V
is less than V
< V
< V
> V
> V
CC
PF
shows the main elements of the serial real-time clock.
PF
PF
PF
PF
, read and write access is allowed after t
is greater than V
, V
, V
, V
, V
PF
CC
CC
CC
CC
is less than V
PF
BACKUP
< V
> V
< V
> V
. However, when V
BACKUP
BACKUP
BACKUP
BACKUP
BACKUP
BACKUP
, the device power is switched from V
Table 2
, the device power is switched from V
, the device power is switched from V
PF
BACKUP
READ/WRITE
. However, when V
ACCESS
specifies several crystal parameters for the external crystal.
Yes
Yes
, the device power is switched from V
No
No
BACKUP
CC
BACKUP
falls below V
CC
source until V
level. The device is fully accessible and data can be written and read
source until V
POWERED
V
CC
BACKUP
V
V
V
BY
REC
falls below V
CC
CC
CC
PF
, the internal clock registers are blocked from any access. If
9 of 20
(Figure
CC
CC
is returned to nominal levels
is returned to nominal levels. The block diagram in
CC
1). On the first application of power to the device the
PF
CC
CC
to V
, the internal clock registers are blocked from any
to V
to V
BACKUP
BACKUP
CC
BACKUP
to V
when V
when V
when V
BACKUP
DS1339 I
CC
CC
when V
CC
(Table
drops below V
drops below V
2
drops below V
C Serial Real-Time Clock
CC
1). After V
drops below V
Figure 3
BACKUP
PF
BACKUP
CC
. If V
shows a
2
returns
C bus.
. The
. The
CC
PF
PF
. If
is
is