ISL12058IRTZ Intersil, ISL12058IRTZ Datasheet - Page 15

• Manufacturer Part Number: ISL12058IRTZ
• Description: IC RTC/CALENDAR I2C-BUS 8-TDFN
• Manufacturer: Intersil
• Type: Clock/Calendar/Alarmr

Specifications of ISL12058IRTZ

• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 1.4 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TDFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -

Application Section
Oscillator Crystal Requirements
The ISL12058 uses a standard 32.768kHz crystal. Either
through hole or surface mount crystals can be used. Table 8
lists some recommended surface mount crystals and the
parameters of each. This list is not exhaustive and other
surface mount devices can be used with the ISL12058 if
their specifications are very similar to the devices listed.
The crystal should have a required parallel load capacitance
of 12.5pF and an equivalent series resistance of less than
50k. The crystal’s temperature range specification should
match the application. Many crystals are rated for -10°C to
+60°C (especially through-hole and tuning fork types), so an
appropriate crystal should be selected if extended
temperature range is required.
.
Layout Considerations
The crystal input at X1 has a very high impedance, and
oscillator circuits operating at low frequencies (such as
32.768kHz) are known to pick up noise very easily if layout
precautions are not followed. Most instances of erratic
clocking or large accuracy errors can be traced to the
susceptibility of the oscillator circuit to interference from
adjacent high speed clock or data lines. Careful layout of the
RTC circuit will avoid noise pickup and insure accurate
clocking.
MANUFACTURER
TABLE 8. SUGGESTED SURFACE MOUNT CRYSTALS
FROM THE
SIGNALS
MASTER
SIGNALS FROM
MicroCrystal
SIGNAL AT
SaRonix
Ecliptek
Raltron
Citizen
THE SLAVE
ECS
Fox
SDA
S
A
R
T
T
1
IDENTIFICATION
1
BYTE WITH
0
R/W = 0
1 1 1 1
15
ECPSM29T-32.768K
0
PART NUMBER
A
C
K
RSM-200S
ECX-306
FSM-327
CM200S
32S12
MS3V
R/W BIT =“0”
FIGURE 11. MULTIPLE BYTES READ SEQUENCE
ADDRESS
BYTE
A
C
K
ISL12058
S
A
R
T
T
IDENTIFICATION
1
BYTE WITH
1
R/W = 1
0
1 1 1 1
Figure 12 shows a suggested layout for the ISL12058 device
using a surface mount crystal. Two main precautions should
be followed:
In addition, it is a good idea to avoid a ground plane under
the X1 and X2 pins and the crystal, as this will affect the load
capacitance and therefore the oscillator accuracy of the
circuit. If the IRQ/F
routed away from the RTC device as well. The traces for the
V
around the crystal.
1. Do not run the serial bus lines or any high speed logic
2. Add a ground trace around the crystal with one end
DD
FIGURE 12. SUGGESTED LAYOUT FOR ISL12058 AND
lines in the vicinity of the crystal. These logic level lines
can induce noise in the oscillator circuit to cause
misclocking.
terminated at the chip ground. This will provide
termination for emitted noise in the vicinity of the RTC
device.
pins can be treated as a ground, and should be routed
1
R/W BIT = “1”
A
C
K
FIRST READ
DATA BYTE
OUT
pin is used as a clock, it should be
A
C
K
A
C
K
LAST READ
DATA BYTE
June 15, 2009
FN6756.0
S
O
P
T