DS1672 Maxim, DS1672 Datasheet - Page 8

• Manufacturer Part Number: DS1672
• Description: The DS1672 low-voltage serial timekeeping chip incorporates a 32-bit counter and power-monitoring functions
• Manufacturer: Maxim

Detailed Description
The DS1672 provides a 32-bit counter that increments once-per-second. The counter data is accessible
via an I
circuit monitors V
prevent data corruption. The device switches to the backup supply input, which maintains oscillator and
counter operation while V
(t
The block diagram in Figure 4 shows the main elements of the DS1672. As shown, communications to
and from the DS1672 occur serially over a I
on the I
identification code followed by a register address. Subsequent registers can be accessed sequentially until
a STOP condition is executed.
Figure 4. Block Diagram
Oscillator Circuit
The DS1672 uses an external 32.768kHz crystal. The oscillator circuit does not require any external
resistors or capacitors to operate. Table 1 specifies several crystal parameters for the external crystal.
Figure 4 shows a functional schematic of the oscillator circuit. If using a crystal with the specified
characteristics, the startup time is usually less than one second.
Table 1. Crystal Specifications*
* The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to Application Note 58:
Clock Accuracy
The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match
between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was
V
PARAMETER
Nominal Frequency
Series Resistance
Load Capacitance
BACKUP
RPU
GND
SDA
RST
SCL
V
CC
) to allow V
2
2
Oscillator
C serial interface. A precision, temperature-compensated, voltage reference and comparator
C bus. Access is obtained by implementing a START condition and providing a device
divider
and
N
CC
CC
to stabilize.
X1
Power Control
I
. When V
C
2
C Interface
L
CC
C
X2
L
is absent. When V
CC
drops below V
SYMBOL
ESR
F
C
O
L
2
Address Register
C, bidirectional bus. The DS1672 operates as a slave device
Control Logic
CC
1Hz
PF
8 of 15
rises above V
, RST becomes active and the interface is disabled to
MIN
Semiconductor
32.768
PF
TYP
6
, RST remains low for a period of time
DS1672
Trickle Charger
32-Bit Counter
Dallas
(4 Bytes)
Control
MAX
45
UNITS
kHz
kΩ
pF
NOTES
DS1672