DS1337_09 Datasheet, PDF (7/16 Pages) Maxim Integrated Products – I2C Serial Real-Time Clock

DS1337 I²C Serial Real-Time Clock
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 trimmed. Crystal
frequency drift caused by temperature shifts creates additional error. External circuit noise coupled into the
oscillator circuit can result in the clock running fast. Figure 1 shows a typical PC board layout for isolating the
crystal and oscillator from noise. Refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks for detailed information.
Figure 1. Typical PC Board Layout for Crystal
LOCAL GROUND PLANE (LAYER 2)
X1
CRYSTAL
X2
GND
NOTE: AVOID ROUTING SIGNALS IN THE CROSSHATCHED
AREA (UPPER LEFT-HAND QUADRANT) OF THE PACKAGE
UNLESS THERE IS A GROUND PLANE BETWEEN THE SIGNAL
LINE AND THE PACKAGE.
DS1337C ONLY
The DS1337C integrates a standard 32,768Hz crystal in the package. Typical accuracy at nominal V_CC and +25°C
is approximately +10ppm. Refer to Application Note 58 for information about crystal accuracy vs. temperature.
OPERATING MODES
The amount of current consumed by the DS1337 is determined, in part, by the I²C interface and oscillator
operation. The following table shows the relationship between the operating mode and the corresponding I_CC
parameter.
Operating Mode
I²C Interface Active
I²C Interface Inactive
I²C Interface Inactive
I²C Interface Inactive
Oscillator Disabled
V_CC
1.8V ≤ V_CC ≤ 5.5V
1.8V ≤ V_CC ≤ 5.5V
1.3V ≤ V_CC ≤ 1.8V
1.3V ≤ V_CC ≤ 1.8V
Power
I_CC Active (I_CCA)
I_CC Standby (I_CCS)
Timekeeping (I_CCTOSC)
Data Retention
(I_CCTDDR)
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