DS1339 Maxim, DS1339 Datasheet - Page 10

• 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

Table 2. Crystal Specifications*
*The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to
Application Note 58: Crystal Considerations for Dallas Real-Time Clocks for additional specifications.
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. Additional
error is added by crystal frequency drift caused by temperature shifts. External circuit noise coupled into the
oscillator circuit may result in the clock running fast.
crystal and oscillator from noise. Refer to Application Note 58: Crystal Considerations with Dallas Real-Time
Clocks for detailed information
DS1339C ONLY
The DS1339C integrates a standard 32,768Hz crystal in the package. Typical accuracy at nominal V
is approximately 10ppm. Refer to Application Note 58 for information about crystal accuracy vs. temperature.
Figure 4. Typical PC Board Layout for Crystal
Nominal Frequency
Series Resistance
Load Capacitance
PARAMETER
LOCAL GROUND PLANE (LAYER 2)
CRYSTAL
SYMBOL
ESR
C
f
O
L
GND
X1
X2
MIN
32.768
TYP
6
10 of 20
Figure 4
NOTE: AVOID ROUTING SIGNALS IN
THE CROSSHATCHED AREA (UPPER
LEFT-HAND QUADRANT) OF THE
PACKAGE UNLESS THERE IS A
GROUND
SIGNAL LINE AND THE PACKAGE.
MAX
50
PLANE
shows a typical PC board layout for isolating the
BETWEEN
UNITS
kHz
kΩ
pF
DS1339 I
THE
2
C Serial Real-Time Clock
CC
and +25°C