ISL12022MIBZ-T Intersil, ISL12022MIBZ-T Datasheet - Page 27

• Manufacturer Part Number: ISL12022MIBZ-T
• Description: IC RTC/CALENDAR TEMP SENS 20SOIC
• Manufacturer: Intersil
• Type: Clock/Calendarr

Specifications of ISL12022MIBZ-T

• Memory Size: 128B
• 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: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ISL12022MIBZ-TCT

Figure 21 shows a suggested layout for the ISL12022M
device. The following main precautions should be
followed:
• Do not run the serial bus lines or any high speed logic
• Add a ground trace around the device with one end
• Be sure to ground pins 6 and 15 as well as pin 8 as
• Add a 0.1µF decoupling capacitor at the device V
The best way to run clock lines around the RTC is to stay
outside of the ground ring by at least a few millimeters.
Also, use the V
they can isolate clock lines from the oscillator section. In
addition, if the IRQ/F
be routed away from the RTC device as well.
FIGURE 21. SUGGESTED LAYOUT FOR THE
lines in the vicinity of pins 1 and 20, or under the
package. These logic level lines can induce noise in
the oscillator circuit, causing misclocking.
terminated at the chip ground. This guard ring will
provide termination for emitted noise in the vicinity of
the RTC device
these all insure the integrity of the device ground
pin, especially when using the 32.768kHz F
function.
FROM THE
SIGNALS
SIGNALS FROM
MASTER
SIGNAL AT
THE SLAVE
SDA
ISL12022M
BAT
S
T
A
R
T
1
IDENTIFICATION
and V
1
OUT
BYTE WITH
0
R/W = 0
1 1 1 1
DD
pin is used as a clock, it should
27
FIGURE 20. READ SEQUENCE (CSR SLAVE ADDRESS SHOWN)
as guard ring lines as well,
0
A
K
C
ADDRESS
BYTE
OUT
GROUND
RING
ISL12022M
F
SCL
SDA
A
C
K
OUT
DD
S
T
A
R
T
IDENTIFICATION
1
1
BYTE WITH
R/W = 1
0
1 1 1 1
Measuring Oscillator Accuracy
The best way to analyze the ISL12022M frequency
accuracy is to set the IRQ/F
frequency, and look at the output of that pin on a high
accuracy frequency counter (at least 7 digits accuracy).
Note that the IRQ/F
require a pull-up resistor.
Using the 1.0Hz output frequency is the most convenient
as the ppm error is expressed in Equation 6:
Other frequencies may be used for measurement but the
error calculation becomes more complex. Use the F
output and a frequency counter for the most accurate
results. Also, when the proper layout guidelines above
are observed, the oscillator should start-up in most
circuits in less than one second.
Temperature Compensation Operation
The ISL12022M temperature compensation feature
needs to be enabled by the user. This must be done in a
specific order as follows.
Note that every time the BETA register is written with the
TSE bit = 1, a temperature compensation cycle is
instigated and a new correction value will be loaded into
the FATR/FDTR registers (if the temperature changed
since the last conversion).
Also note that registers 0Bh and 0Ch, the ITR0 and
ALPHA registers, are READ-ONLY, and cannot be written
to. Also the value for BETA is locked and cannot be
changed with a write. However, It is still a good idea to
do the bit masking when doing TSE bit changes.
ppm error
1. Read register 0Dh, the BETA register. This register
2. Bit 7 of the BETA register is the master enable
3. Bits 5 and 6 of the BETA register control
4. Write back to register 0Dh making sure not to
contains the 5-bit BETA trimmed value, which is
automatically loaded on initial power-up. Mask off
the 5 LSB’s of the value just read.
control for temperature sense operation. Set this to
“1” to allow continuous temperature frequency
correction. Frequency correction will then happen
every 60 seconds with V
temperature compensation in battery backup mode
(see Table 15). Set the values for the operation
desired.
change the 5 LSB values, and include the desired
compensation control bits.
1
=
A
K
C
F
OUT
FIRST READ
DATA BYTE
–
1 1e6
•
OUT
is an drain output and will
A
C
K
OUT
DD
pin for a specific
applied.
A
C
K
LAST READ
DATA BYTE
June 4, 2010
FN6668.7
(EQ. 6)
OUT
O
S
T
P