ISL12027IBAZ Intersil, ISL12027IBAZ Datasheet - Page 23

• Manufacturer Part Number: ISL12027IBAZ
• Description: IC RTC/CALENDAR EEPROM 8-SOIC
• Manufacturer: Intersil
• Type: Clock/Calendar/Supervisor/EEPROMr

Specifications of ISL12027IBAZ

• Memory Size: 4K (512 x 8)
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

circuit and produce double clocking or mis-clocking, seriously
affecting the accuracy of the RTC. Care needs to be taken in
layout of the RTC circuit to avoid noise pickup. Figure 27 shows
a suggested layout for the ISL12027 or ISL12026 devices.
The X1 and X2 connections to the crystal are to be kept as
short as possible. A thick ground trace around the crystal is
Oscillator Measurements
When a proper crystal is selected and the layout guidelines
above are observed, the oscillator should start up in most
circuits in less than one second. Some circuits may take slightly
longer, but start-up should definitely occur in less than 5s.
When testing RTC circuits, the most common impulse is to
FIGURE 27. SUGGESTED LAYOUT FOR INTERSIL RTC IN SO-8
Frequency
Frequency Tolerance
Turnover Temperature
Operating Temperature Range
Parallel Load Capacitance
Equivalent Series Resistance
Citizen
Epson
Raltron
SaRonix
Ecliptek
ECS
Fox
MANUFACTURER
PARAMETER
CM201, CM202, CM200S
32S12A or B
ECX-306/ECX-306I
FSM-327
MC-405, MC-406
RSM-200S-A or B
ECPSM29T-32.768K
23
32.768kH
TABLE 8. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL RTC’S
XTAL1
PART NUMBER
ISL12027
R
1
U
Z
1
10k
MIN
-40
20
TABLE 9. CRYSTAL MANUFACTURERS
ISL12027, ISL12027A
C
01µF
32.768
1
TYP
12.5
25
TEMP RANGE (°C)
MAX
±100
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-10 to +60
-10 to +60
-40 to +85
30
85
50
advised to minimize noise intrusion, but ground near the X1
and X2 pins should be avoided as it will add to the load
capacitance at those pins. Keep in mind these guidelines for
other PCB layers in the vicinity of the RTC device. A small
decoupling capacitor at the V
with a solid connection to ground (see Figure 27).
apply a scope probe to the circuit at the X2 pin (oscillator
output) and observe the waveform. DO NOT DO THIS!
Although in some cases you may see a usable waveform, due
to the parasitics (usually 10pF to ground) applied with the
scope probe, there will be no useful information in that
waveform other than the fact that the circuit is oscillating. The
X2 output is sensitive to capacitive impedance so the voltage
levels and the frequency will be affected by the parasitic
elements in the scope probe. Applying a scope probe can
possibly cause a faulty oscillator to start-up, hiding other issues
(although in the Intersil RTC’s, the internal circuitry assures
startup when using the proper crystal and layout).
The best way to analyze the RTC circuit is to power it up and
read the real time clock as time advances. Alternatively the
frequency can be checked by setting an alarm for each minute.
Using the pulse interrupt mode setting, the once-per-minute
interrupt functions as an indication of proper oscillation.
Backup Battery Operation
Many types of batteries can be used with the Intersil RTC
products. 3.0V or 3.6V Lithium batteries are appropriate, and
sizes are available that can power a Intersil RTC device for
up to 10 years. Another option is to use a supercapacitor for
applications where V
short periods of time. Depending on the value of
UNITS
ppm
kHz
k
°C
°C
pF
Ω
+25°C FREQUENCY TOLERANCE (ppm)
DD
Down to 20ppm if desired
Typically the value used for most crystals
For best oscillator performance
may disappear intermittently for
DD
pin of the chip is mandatory,
NOTES
±20
±20
±20
±20
±20
±20
±20
August 12, 2010
FN8232.8