ISL12028IB27Z-T Intersil, ISL12028IB27Z-T Datasheet - Page 24

• Manufacturer Part Number: ISL12028IB27Z-T
• Description: IC RTC/CALENDAR EEPROM 14-SOIC
• Manufacturer: Intersil
• Type: Clock/Calendar/Supervisor/EEPROMr

Specifications of ISL12028IB27Z-T

• 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
• Bus Type: Serial (I2C)
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• Operating Temperature Classification: Industrial
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ISL12028IB27Z-TTR

The X1 and X2 connections to the crystal are to be kept as
short as possible. A thick ground trace around the crystal is
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.
For other RTC products, the same rules stated previously
should be observed, but adjusted slightly since the packages
and pinouts are slightly different.
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 startup should definitely occur in less than
5 seconds. When testing RTC circuits, the most common
impulse is to 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
(X1228
MODE
mode)
A
B
C
D
TABLE 11. I
SBIB
BIT
0
0
1
1
2
C, LV RESET, AND BATTERY BACKUP OPERATION SUMMARY (SHADED ROW IS SAME AS X1228 OPERATION)
BSW
BIT
0
1
0
1
V
V
Standard Mode,
Standard Mode,
24
DD
SWITCHOVER
TRIP
Legacy Mode,
Legacy Mode,
TRIP
V
V
ISL12028A
VOLTAGE
Default for
Default for
ISL12028,
DD
DD
pin of the chip is mandatory,
V
= 2.2V typ,
= 2.2V typ
BAT
< V
< V
BAT
BAT
V
I
2
BAT
C ACTIVE IN
YES, only if
BACKUP?
BATTERY
ISL12028, ISL12028A
> V
NO
NO
NO
RESET
READ IN BATTERY
EE PROM WRITE/
YES, read only
BACKUP?
NO
NO
NO
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, or if the chip has
the IRQ/F
oscilloscope (after enabling it with the control register, and
using a pull-up resistor for the open-drain output).
Alternatively, the ISL12028 IRQ/F
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.
OUT
IRQ/FREQ
ACTIVE?
output, look at the output of that pin on an
YES
YES
YES
YES
Operation of I
V
communications. Battery switchover
at V
Operation of I
backup mode, but only for
V
Bus must have pull-ups to V
nonvolatile writes with V
Operation of I
V
communications. Battery switchover
at V
Operation of I
or V
DD
BAT
DD
TRIP
TRIP
BAT
= V
= V
>V
, whichever is higher.
OUT
DD
.
.
RESET
RESET
>V
- output can be
2
RESET
2
2
2
C bus down to V
C bus down to
, then below that no
C bus into battery
C bus down to
, then below that no
NOTES
.
November 30, 2010
BAT
>V
BAT
FN8233.9
DD
RESET
. No