ISL12008 Datasheet, PDF (6/19 Pages) Intersil Corporation – I2C Real Time Clock with Battery Backup

ISL12008
Typical Performance Curves Temperature is +25°C, unless otherwise specified.
0.2
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.8
2.3
2.8
3.3
3.8
4.3
4.8
5.3
V_BAT (V)
FIGURE 1. I_BAT vs V_BAT
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 2. I_BAT vs TEMPERATURE AT V_BAT = 3V
3.5
V_DD = 5V
3.0
2.5
2.0
V_DD = 3.3V
1.5
1.0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
FIGURE 3. I_DD1 vs TEMPERATURE
3.5
3.0
2.5
LP MODE OFF
2.0
1.5
LP MODE ON
1.0
0.5
1.8 2.3 2.8 3.3 3.8 4.3 4.8 5.3
V_DD (V)
FIGURE 4. I_DD1 vs V_DD WITH LPMODE ON AND OFF
EQUIVALENT AC OUTPUT LOAD CIRCUIT FOR V_DD = 5V
5.0V
SDA
AND
FT/OUT
1533Ω
FOR V_OL= 0.4V
AND I_OL = 3mA
100pF
FIGURE 5. STANDARD OUTPUT LOAD FOR TESTING THE
DEVICE WITH V_DD = 5.0V
General Description
The ISL12008 device is a low power real time clock with
timing and crystal compensation, clock/calendar, power fail
indicator, software alarm, and intelligent battery backup
switching.
The oscillator uses an external, low-cost 32.768kHz crystal.
The real time clock tracks time with separate registers for
hours, minutes, seconds, and sub-seconds. The device has
calendar registers for date, month, year and day of the week.
The calendar is accurate through 2099, with automatic leap
year correction.
The ISL12008's powerful alarm can be set to any
clock/calendar value for a match. For example, every
minute, every Tuesday or at 5:23 AM on March 21. The
alarm status is available by checking the Status Register.
The device also offers a backup power input pin. This V_BAT
pin allows the device to be backed up by battery or super
capacitor with automatic switchover from V_DD to V_BAT. The
entire ISL12008 device is fully operational from 2.7V to 5.5V
and the clock/calendar portion of the device remains fully
operational down to 1.8V in battery mode.
Pin Descriptions
X1, X2
The X1 and X2 pins are the input and output, respectively, of
an inverting amplifier. An external 32.768kHz quartz crystal is
used with the ISL12008 to supply a timebase for the real time
clock. Internal compensation circuitry provides high accuracy
over the operating temperature range from -40°C to +85°C.
This oscillator compensation network can be used to calibrate
6
FN6690.1
September 26, 2008