ISL12028IB27Z Intersil, ISL12028IB27Z Datasheet - Page 23

• Manufacturer Part Number: ISL12028IB27Z
• Description: IC RTC W/EEPROM 2.7V 14SOIC
• Manufacturer: Intersil
• Type: Clock/Calendar/Supervisor/EEPROMr

Specifications of ISL12028IB27Z

• 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: 14-SOIC (3.9mm Width), 14-SOL
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

A final application for the ATR control is in-circuit calibration
for high accuracy applications, along with a temperature
sensor chip. Once the RTC circuit is powered up with battery
backup, the IRQ/F
frequency drift is measured. The ATR control is then
adjusted to a setting which minimizes drift. Once adjusted at
a particular temperature, it is possible to adjust at other
discrete temperatures for minimal overall drift, and store the
resulting settings in the EEPROM. Extremely low overall
temperature drift is possible with this method. The Intersil
evaluation board contains the circuitry necessary to
implement this control.
Layout Considerations
The crystal input at X1 has a very high impedance and will
pick up high frequency signals from other circuits on the
board. Since the X2 pin is tied to the other side of the crystal,
it is also a sensitive node. These signals can couple into the
oscillator circuit and produce double clocking or misclocking,
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 ISL12029 or
ISL12028 devices (R1 is not needed for the ISL12028).
Frequency
Frequency Tolerance
Turnover-Temperature
Operating Temperature Range
Parallel Load Capacitance
Equivalent Series Resistance
Citizen
Epson
Raltron
SaRonix
Ecliptek
ECS
Fox
MANUFACTURER
PARAMETER
OUT
output is set at 32.768kHz and
23
TABLE 9. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL RTC
CM201, CM202, CM200S
MC-405, MC-406
RSM-200S-A or B
32S12A or B
ECPSM29T-32.768K
ECX-306/ECX-306I
FSM-327
MIN
-40
TABLE 10. CRYSTAL MANUFACTURERS
20
PART NUMBER
ISL12028, ISL12028A
32.768
TYP
12.5
25
MAX
±100
30
85
50
.
FIGURE 27. SUGGESTED LAYOUT FOR INTERSIL RTC IN SO-14
32.768kHz
32.768kGz
XTAL1
XTAL1
UNITS
ppm
kHz
k
°C
°C
pF
Ω
TEMP RANGE
-40 to +85
-40 to +85
-40 to +85
-40 to +85
-10 to +60
-10 to +60
-40 to +85
(°C)
Down to 20ppm if desired
Typically the value used for most crystals
For best oscillator performance
ISL12028
X1228
U1
U1
R1
R1 10k
NOTES
+25°C FREQUENCY
10k
TOLERANCE
(ppm)
±20
±20
±20
±20
±20
±20
±20
November 30, 2010
FN8233.9
C1
C1
0.1µF
0.1µF