DATASHEET

ISL12027, ISL12027A
®
Data Sheet
August 12, 2010
FN8232.8
Real Time Clock/Calendar with EEPROM
Features
The ISL12027 device is a low power real time clock with
timing and crystal compensation, clock/calender, power-fail
indicator, two periodic or polled alarms, intelligent battery
backup switching, CPU Supervisor and integrated 512x8-bit
EEPROM, in 16 Byte per page format.
• Real Time Clock/Calendar
- Tracks Time in Hours, Minutes and Seconds
- Day of the Week, Day, Month and Year
The oscillator uses an external, low-cost 32.768kHz crystal.
The real time clock tracks time with separate registers for
hours, minutes, and 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 ISL12027 and ISL12027A Power Control Settings are
different. The ISL12027 uses the Legacy Mode Setting, and
the ISL12027A uses the Standard Mode Setting.
Applications that have VBAT > VDD will require only the
ISL12027A. Please refer to“Power Control Operation” on
page 15 for more details. Also, please refer to “I2C
Communications During Battery Backup and LVR Operation”
on page 24 for important details.
Pinouts
ISL12027, ISL12027A
(8 LD TSSOP)
TOP VIEW
• Two Non-Volatile Alarms
- Settable on the Second, Minute, Hour, Day of the Week,
Day, or Month
- Repeat Mode (Periodic Interrupts)
• Automatic Backup to Battery or SuperCap
• On-Chip Oscillator Compensation
- Internal Feedback Resistor and Compensation
Capacitors
- 64 Position Digitally Controlled Trim Capacitor
- 6 Digital Frequency Adjustment Settings to ±30ppm
• 512x8-Bits of EEPROM
- 16-Byte Page Write Mode (32 total pages)
- 8 Modes of BlockLock™ Protection
- Single Byte Write Capability
• High Reliability
- Data Retention: 50 years
- Endurance: >2,000,000 Cycles Per Byte
• I2C-bus™ Interface
- 400kHz Data Transfer Rate
VBAT
1
8
SCL
VDD
2
7
SDA
• 800nA Battery Supply Current
• Package Options
- 8 Ld SOIC and 8 Ld TSSOP Packages
X1
3
6
GND
X2
4
5
RESET
• Pb-Free (RoHS Compliant)
ISL12027, ISL12027A
(8 LD SOIC)
TOP VIEW
Applications
• Utility Meters
• HVAC Equipment
X1
1
8
VDD
X2
2
7
VBAT
• Audio/Video Components
RESET
3
6
SCL
• Modems
GND
4
5
SDA
• Network Routers, Hubs, Switches, Bridges
• Cellular Infrastructure Equipment
• Fixed Broadband Wireless Equipment
• Pagers/PDA
• POS Equipment
• Test Meters/Fixtures
• Office Automation (Copiers, Fax)
• Home Appliances
• Computer Products
• Other Industrial/Medical/Automotive
1
I
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
is a trademark of NXP B.V., BlockLock™ is a trademark of Intersil Corporation or one of its subsidiaries
Copyright Intersil Americas Inc. 2005, 2006, 2010. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
2C-bus™
ISL12027, ISL12027A
Pin Descriptions
PIN NUMBER
SOIC
TSSOP
SYMBOL
BRIEF DESCRIPTION
1
3
X1
The X1 pin is the input of an inverting amplifier and is intended to be connected to one pin of an external
32.768kHz quartz crystal. X1 can also be driven directly from a 32.768kHz source.
2
4
X2
The X2 pin is the output of an inverting amplifier and is intended to be connected to one pin of an external
32.768kHz quartz crystal.
3
5
RESET
RESET. This is a reset signal output. This signal notifies a host processor that the “watchdog” time period
has expired or that the voltage has dropped below a fixed VTRIP threshold. It is an open drain active LOW
output. Recommended value for the pull-up resistor is 5kΩ. If unused, connect to ground.
4
6
GND
Ground.
5
7
SDA
Serial Data (SDA) is a bidirectional pin used to transfer serial data into and out of the device. It has an
open drain output and may be wire OR’ed with other open drain or open collector outputs.
6
8
SCL
The Serial Clock (SCL) input is used to clock all serial data into and out of the device. The input buffer on
this pin is always active (not gated).
7
1
VBAT
This input provides a backup supply voltage to the device. VBAT supplies power to the device in the event
that the VDD supply fails. This pin should be tied to ground if not used.
8
2
VDD
Power Supply.
Ordering Information
PART
NUMBER
(Notes 1, 2, 3)
PART
MARKING
VBAT TRIP POINT
(V)
BSW BIT DEFAULT
SETTING
VRESET
VOLTAGE
(V)
TEMP. RANGE
(°C)
PACKAGE
(Pb-Free)
PKG.
DWG. #
ISL12027IB27Z
12027 IB27Z
VDD < VBAT
BSW = 1
2.63
-40 to +85
8 Ld SOIC
M8.15
ISL12027IB27AZ
12027 IB27AZ
VDD < VBAT
BSW = 1
2.92
-40 to +85
8 Ld SOIC
M8.15
ISL12027IB30AZ
12027 IB30AZ
VDD < VBAT
BSW = 1
3.09
-40 to +85
8 Ld SOIC
M8.15
ISL12027IBZ
12027 IBZ
VDD < VBAT
BSW = 1
4.38
-40 to +85
8 Ld SOIC
M8.15
ISL12027IBAZ
12027 IBAZ
VDD < VBAT
BSW = 1
4.64
-40 to +85
8 Ld SOIC
M8.15
ISL12027IV27Z
2027 I27Z
VDD < VBAT
BSW = 1
2.63
-40 to +85
8 Ld TSSOP
M8.173
ISL12027IV27AZ
2027 27AZ
VDD < VBAT
BSW = 1
2.92
-40 to +85
8 Ld TSSOP
M8.173
ISL12027IV30AZ
2027 30AZ
VDD < VBAT
BSW = 1
3.09
-40 to +85
8 Ld TSSOP
M8.173
ISL12027IVZ
2027 IVZ
VDD < VBAT
BSW = 1
4.38
-40 to +85
8 Ld TSSOP
M8.173
ISL12027IVAZ
2027 IVAZ
VDD < VBAT
BSW = 1
4.64
-40 to +85
8 Ld TSSOP
M8.173
ISL12027AIB27Z
12027A IB27Z
VDD < VBAT
BSW = 0
2.63
-40 to +85
8 Ld SOIC
M8.15
ISL12027AIV27Z
2027A I27Z
VDD < VBAT
BSW =0
2.63
-40 to +85
8 Ld TSSOP
M8.173
NOTES:
1. Add “-T” suffix for tape and reel. Please refer to TB347 for details on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte
tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil
Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD020.
3. For Moisture Sensitivity Level (MSL), please see device information page for ISL12027, ISL12027A. For more information on MSL please see
techbrief TB363.
2
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Block Diagram
OSC COMPENSATION
X1
OSCILLATOR
X2
SCL
SDA
CONTROL
SERIAL
INTERFACE DECODE
LOGIC
DECODER
CONTROL/
REGISTERS
(EEPROM)
TIMER
FREQUENCY 1Hz CALENDAR
DIVIDER
LOGIC
STATUS
REGISTERS
(SRAM)
8
WATCHDOG
TIMER
RESET
3
LOW VOLTAGE
RESET
TIME
KEEPING
REGISTERS
(SRAM)
BATTERY
SWITCH
CIRCUITRY
VDD
VBAT
COMPARE
ALARM
MASK
32.768kHZ
ALARM REGS
(EEPROM)
4k
EEPROM
ARRAY
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Absolute Maximum Ratings
Thermal Information
Voltage on VDD, VBAT, SCL, SDA, and RESET pins
(respect to ground) . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
Voltage on X1 and X2 pins
(respect to ground) . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 2.5V
Latchup (Note 4) . . . . . . . . . . . . . . . . . . . Class II, Level B @ +85°C
ESD Rating
Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±2kV
Machine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175V
Thermal Resistance (Typical)
θJA (°C/W)
θJC (°C/W)
8 Ld SOIC Package (Notes 5, 6) . . . . .
115
50
8 Ld TSSOP Package (Notes 5, 6) . . .
140
40
Maximum Junction Temperature (Plastic Package) . . . . . . . +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and
result in failures not covered by warranty.
NOTES:
4. Jedec Class II pulse conditions and failure criterion used. Level B exceptions are: Using a max positive pulse of 8.35V on all pins except X1 and
X2, Using a max positive pulse of 2.75V on X1 and X2, and using a max negative pulse of -1V for all pins.
5. θJA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
6. For θJC, the “case temp” location is taken at the package top center.
Unless otherwise noted, VDD = +2.7V to +5.5V, TA = -40°C to +85°C, Typical values are at TA = +25°C and
VDD = 3.3V. Boldface limits apply over the operating temperature range, -40°C to +85°C.
DC Electrical Specifications
SYMBOL
PARAMETER
CONDITIONS
MIN
(Note 16)
TYP
MAX
(Note 16)
UNIT
VDD
Main Power Supply
2.7
5.5
V
VBAT
Backup Power Supply
1.8
5.5
V
Electrical Specifications
IDD2
IDD3
IBAT
Boldface limits apply over the operating temperature range, -40°C to +85°C.
MAX
(Note 16)
UNIT
NOTES
VDD = 2.7V
500
µA
7, 8, 9
VDD = 5.5V
800
µA
VDD = 2.7V
2.5
mA
VDD = 5.5V
3.5
mA
Supply Current for Main
Timekeeping (Low Power Mode)
VDD = VSDA = VSCL = 2.7V
10
µA
VDD = VSDA = VSCL = 5.5V
20
µA
Battery Supply Current
VBAT = 1.8V,
VDD = VSDA = VSCL= VRESET = 0V
800
1000
nA
VBAT = 3.0V,
VDD = VSDA = VSCL= VRESET = 0V
850
1200
nA
100
nA
2.6
V
11
SYMBOL
IDD1
NOTES
PARAMETER
Supply Current with
I2C
Active
Supply Current for Non-Volatile
Programming
IBATLKG
Battery Input Leakage
VTRIP
VBAT Mode Threshold
CONDITIONS
VDD = 5.5V, VBAT = 1.8V
MIN
(Note 16)
TYP
-100
1.8
2.2
7, 8, 9
9
7, 10, 11
VTRIPHYS VTRIP Hysteresis
30
mV
11, 14
VBATHYS
VBAT Hysteresis
50
mV
11, 14
VDD SR-
VDD Negative Slew rate
10
V/ms
12
VDD = 5.5V
IOL = 3mA
0.4
V
VDD = 2.7V
IOL = 1mA
0.4
V
400
nA
RESET OUTPUT
VOL
ILO
Output Low Voltage
Output Leakage Current
4
VDD = 5.5V
VOUT = 5.5V
100
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Watchdog Timer/Low Voltage Reset Parameters
SYMBOL
tRPD
PARAMETER
CONDITIONS
MIN
(Note 16)
TYP
(Note 5)
VDD Detect to RESET LOW
MA
(Note 16)
500
UNITS
NOTES
ns
13
tPURST
Power-up Reset Time-Out Delay
100
VRVALID
Minimum VDD for Valid RESET
Output
1.0
VRESET
ISL12027-4.5A Reset Voltage Level
4.59
4.64
4.69
V
ISL12027 Reset Voltage Level
4.33
4.38
4.43
V
ISL12027-3 Reset Voltage Level
3.04
3.09
3.14
V
ISL12027-2.7A Reset Voltage Level
2.87
2.92
2.97
V
ISL12027-2.7 Reset Voltage Level
2.58
2.63
2.68
V
1.70
1.75
1.801
s
725
750
775
ms
225
250
275
ms
225
250
275
ms
tWDO
Watchdog Timer Period
tRST
Watchdog Timer Reset Time-Out
Delay
tRSP
I2C Interface Minimum Restart Time
32.768kHz crystal between X1
and X2
32.768kHz crystal between X1
and X2
250
400
ms
V
1.2
µs
>2,000,000
Cycles
50
Years
EEPROM SPECIFICATIONS
EEPROM Endurance
Temperature ≤ +75°C
EEPROM Retention
Serial Interface (I2C) Specifications
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VIL
SDA, and SCL Input Buffer LOW
Voltage
SBIB = 1 (Under VDD mode)
-0.3
0.3xVDD
V
VIH
SDA, and SCL Input Buffer HIGH
Voltage
SBIB = 1 (Under VDD mode)
0.7xVDD
VDD + 0.3
V
SBIB = 1 (Under VDD mode)
0.05xVDD
Hysteresis SDA and SCL Input Buffer
Hysteresis
VOL
SDA Output Buffer LOW Voltage
IOL = 4mA
ILI
Input Leakage Current on SCL
VIN = 5.5V
ILO
I/O Leakage Current on SDA
VIN = 5.5V
NOTES
V
0
0.4
V
0.1
10
µA
0.1
10
µA
400
kHz
TIMING CHARACTERISTICS
fSCL
SCL Frequency
tIN
Pulse Width Suppression Time at
SDA and SCL Inputs
Any pulse narrower than the max spec
is suppressed.
50
ns
tAA
SCL Falling Edge to SDA Output
Data Valid
SCL falling edge crossing 30% of VDD,
until SDA exits the 30% to 70% of VDD
window.
900
ns
tBUF
Time the Bus Must be Free Before
the Start of a New Transmission
SDA crossing 70% of VDD during a
STOP condition, to SDA crossing 70%
of VDD during the following START
condition.
1300
ns
tLOW
Clock LOW Time
Measured at the 30% of VDD crossing.
1300
ns
tHIGH
Clock HIGH Time
Measured at the 70% of VDD crossing.
600
ns
5
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Serial Interface (I2C) Specifications (Continued)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NOTES
tSU:STA
START Condition Set-up Time
SCL rising edge to SDA falling edge.
Both crossing 70% of VDD.
600
ns
tHD:STA
START Condition Hold Time
From SDA falling edge crossing 30%
of VDD to SCL falling edge crossing
70% of VDD.
600
ns
tSU:DAT
Input Data Set-up Time
From SDA exiting the 30% to 70% of
VDD window, to SCL rising edge
crossing 30% of VDD.
100
ns
tHD:DAT
Input Data Hold Time
From SCL falling edge crossing 70% of
VDD to SDA entering the 30% to 70%
of VDD window.
0
ns
tSU:STO
STOP Condition Set-up Time
From SCL rising edge crossing 70% of
VDD, to SDA rising edge crossing 30%
of VDD.
600
ns
tHD:STO
STOP Condition Hold Time for
Read, or Volatile Only Write
From SDA rising edge to SCL falling
edge. Both crossing 70% of VDD.
600
ns
Output Data Hold Time
From SCL falling edge crossing 30% of
VDD, until SDA enters the 30% to 70%
of VDD window.
0
ns
tR
SDA and SCL Rise Time
From 30% to 70% of VDD
20 +
0.1xCb
250
ns
tF
SDA and SCL Fall Time
From 70% to 30% of VDD
20 +
0.1xCb
250
ns
10
pF
20
ms
14
tDH
Cpin
SDA, and SCL Pin Capacitance
tWC
Non-Volatile Write Cycle Time
12
tR
SDA and SCL Rise Time
From 30% to 70% of VDD
20 +
0.1xCb
250
ns
15
tF
SDA and SCL Fall Time
From 70% to 30% of VDD
20 +
0.1xCb
250
ns
15
Cb
Capacitive Loading of SDA or SCL Total on-chip and off-chip
10
400
pF
15
SDA and SCL Bus Pull-up Resistor Maximum is determined by tR and tF.
Off-chip
For Cb = 400pF, max is about
2kΩ~2.5kΩ.
For Cb = 40pF, max is about
15kΩ~20kΩ
1
kΩ
15
RPU
NOTES:
7. RESET Inactive (no reset).
8. VIL = VDD x 0.1, VIH = VDD x 0.9, fSCL = 400kHz.
9. VRESET = 2.63V (VDD must be greater than VRESET), VBAT = 0V.
10. Bit BSW = 0 (Standard Mode), ATR = 00h, VBAT ≥1.8V.
11. Specified at +25°C.
12. In order to ensure proper timekeeping, the VDD SR- specification must be followed.
13. Parameter is not 100% tested.
14. tWC is the minimum cycle time to be allowed for any non-volatile Write by the user, it is the time from valid STOP condition at the end of Write
sequence of a serial interface Write operation, to the end of the self-timed internal non-volatile write cycle.
15. These are I2C specific parameters and are not directly tested, however they are used during device testing to validate device specification.
16. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by
characterization and are not production tested.
6
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Timing Diagrams
tF
SCL
tHIGH
tLOW
tHD:STO
tR
tSU:DAT
tSU:STA
tHD:DAT
tSU:STO
tHD:STA
SDA
(INPUT TIMING)
tAA
tDH
tBUF
SDA
(OUTPUT TIMING)
FIGURE 1. BUS TIMING
SCL
8TH BIT OF LAST BYTE
SDA
ACK
tWC
STOP
CONDITION
START
CONDITION
FIGURE 2. WRITE CYCLE TIMING
tRSP
tRSP>tWDO
tRSP>tWDO
tRSP<tWDO
tRST
tRST
SCL
SDA
RESET
START
STOP START
Note: All inputs are ignored during the active reset period (tRST).
FIGURE 3. WATCHDOG TIMING
VRESET
VDD
tPURST
tPURST
tRPD
tF
tR
RESET
VRVALID
FIGURE 4. RESET TIMING
7
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Typical Performance Curves
Temperature is +25°C unless otherwise specified.
0.9
4.0
BSW = 0 OR 1
3.5
0.8
0.7
SCL, SDA PULL-UPS = 0V
3.0
IBAT (µA)
2.5
IBAT (µA)
SCL, SDA PULL-UPS = 0V
BSW = 0 OR 1
0.6
2.0
1.5
1.0
SCL, SDA PULL-UPS = VBAT
0.5
BSW = 0 OR 1
0.0
1.8
2.3
2.8
3.3
3.8
0.5
0.4
0.3
0.2
0.1
4.3
4.8
0.0
1.8
5.3
2.3
2.8
3.3
FIGURE 5. IBAT vs VBAT, SBIB = 0
4.8
5.3
1.4
4.5
1.2
VDD = 5.5V
4.0
VBAT = 3.0V
1.0
IBAT (µA)
3.5
IDD (µA)
4.3
FIGURE 6. IBAT vs VBAT, SBIB = 1
5.0
VDD = 3.3V
3.0
2.5
2.0
1.5
0.8
0.6
0.4
1.0
0.2
0.5
0.0
-45 -35 -25 -15
-5
5 15 25 35 45
TEMPERATURE (°C)
55
65
75
0.0
-45 -35 -25 -15
85
FIGURE 7. IDD3 vs TEMPERATURE
-5
5 15 25 35 45
TEMPERATURE (°C)
55
65
75
85
FIGURE 8. IBAT vs TEMPERATURE
80
4.5
PPM CHANGE FROM ATR = 0
4.0
3.5
3.0
IDD (µA)
3.8
VBAT(V)
VBAT (V)
2.5
2.0
1.5
1.0
0.5
0.0
1.8
2.3
2.8
3.3
3.8
4.3
VDD (V)
FIGURE 9. IDD3 vs VDD
8
4.8
5.3
60
40
20
0
-20
-40
-32 -28 -24 -20 -16 -12 -8 -4
0
4
8
12 16 20 24 28
ATR SETTING
FIGURE 10. ΔFOUT vs ATR SETTING
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Description
The ISL12027 device is a Real Time Clock with
clock/calendar, two polled alarms with integrated 512x8
EEPROM configured in 16 Byte per page format, oscillator
compensation, CPU Supervisor (Power on Reset, Low
Voltage Sensing and Watchdog Timer) and battery backup
switch.
This open drain output requires the use of a pull-up resistor.
The pull-up resistor on this pin must use the same voltage
source as VDD. The output circuitry controls the fall time of
the output signal with the use of a slope controlled
pull-down. The circuit is designed for 400kHz I2C interface
speed.
VBAT
The oscillator uses an external, low-cost 32.768kHz crystal.
All compensation and trim components are integrated on the
chip. This eliminates several external discrete components
and a trim capacitor, saving board area and component cost.
This input provides a backup supply voltage to the device.
VBAT supplies power to the device in the event the VDD
supply fails. This pin can be connected to a battery, a
SuperCap or tied to ground if not used.
The Real-Time Clock keeps track of time with separate
registers for Hours, Minutes and Seconds. The Calendar has
separate registers for Date, Month, Year and Day-of-week.
The calendar is correct through 2099, with automatic leap
year correction.
Note that the device is not guaranteed to operate with
VBAT < 1.8V. If the battery voltage is expected to drop lower
than this minimum, correct operation of the device,
(especially after a VDD power-down cycle) is not guaranteed.
The Dual Alarms can be set to any Clock/Calendar value for
a match. For instance, every minute, every Tuesday, or 5:23
AM on March 21. The alarms can be polled in the Status
Register. There is a repeat mode for the alarms allowing a
periodic interrupt.
The RESET signal output can be used to notify a host
processor that the Watchdog timer has expired or the VDD
voltage supply has dipped below the VRESET threshold. It is
an open drain, active LOW output. Recommended value for
the pull-up resistor is 5kΩ. If unused it can be tied to ground.
The ISL12027 device integrates CPU Supervisory functions
(POR, WDT) and Battery Switch. There is Power-On-Reset
(RESET) output with 250ms delay from power on. It will also
assert RESET when VDD goes below the specified
threshold. The Vtrip threshold is selectable via VTS2/VTS1/
VTS0 registers to five (5) preselected levels. There is
Watchdog Timer (WDT) with 3 selectable time-out periods
(0.25s, 0.75s and 1.75s) and disabled setting. The
Watchdog Timer activates the RESET pin when it expires.
In battery mode, the Watchdog timer function is disabled.
The RESET signal output is asserted LOW when the VDD
voltage supply has dipped below the VRESET threshold but
the RESET signal output will not return HIGH until the device
is back to VDD mode (out of Battery Backup mode) even if
the VDD voltage is above VRESET threshold.
The device offers a backup power input pin. This VBAT pin
allows the device to be backed up by battery or SuperCap.
The entire ISL12027 device is fully operational from 2.7V to
5.5V and the clock/calendar portion of the ISL12027 device
remains fully operational down to 1.8V (Standby Mode).
The ISL12027 device provides 4k bits of EEPROM with
8 modes of BlockLock™ control. The BlockLock™ allows a
safe, secure memory for critical user and configuration data,
while allowing a large user storage area.
RESET
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 ISL12027 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 the crystal timing accuracy over
temperature either during manufacturing or with an external
temperature sensor and microcontroller for active
compensation. X2 is intended to drive a crystal only, and
should not drive any external circuit (Figure 11).
NO EXTERNAL COMPENSATION RESISTORS OR
CAPACITORS ARE NEEDED OR ARE RECOMMENDED
TO BE CONNECTED TO THE X1 AND X2 PINS.
Pin Descriptions
Serial Clock (SCL)
The SCL input is used to clock all data into and out of the
device. The input buffer on this pin is always active (not
gated). The pull-up resistor on this pin must use the same
voltage source as VDD.
X1
X2
Serial Data (SDA)
SDA is a bi-directional pin used to transfer data into and out
of the device. It has an open drain output and may be wire
ORed with other open drain or open collector outputs. The
input buffer is always active (not gated).
9
FIGURE 11. RECOMMENDED CRYSTAL CONNECTION
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Real Time Clock Operation
Clock/Control Registers (CCR)
The Real Time Clock (RTC) uses an external 32.768kHz
quartz crystal to maintain an accurate internal representation
of the second, minute, hour, day, date, month and year. The
RTC has leap-year correction. The clock also corrects for
months having fewer than 31 days and has a bit that controls
24 hour or AM/PM format. When the ISL12027 powers up
after the loss of both VDD and VBAT, the clock will not
operate until at least one byte is written to the clock register.
The Control/Clock Registers are located in an area separate
from the EEPROM array and are only accessible following a
slave byte of “1101111x” and reads or writes to addresses
[0000h:003Fh]. The clock/control memory map has memory
addresses from 0000h to 003Fh. The defined addresses are
described in Table 2. Writing to and reading from the
undefined addresses are not recommended.
Reading the Real Time Clock
The contents of the CCR can be modified by performing a
byte or a page write operation directly to any address in the
CCR. Prior to writing to the CCR (except the status register),
however, the WEL and RWEL bits must be set using a three
step process (see “Writing to the Clock/Control Registers” on
page 14).
The RTC is read by initiating a Read command and
specifying the address corresponding to the register of the
Real Time Clock. The RTC Registers can then be read in a
Sequential Read Mode. Since the clock runs continuously
and read takes a finite amount of time, there is a possibility
that the clock could change during the course of a read
operation. In this device, the time is latched by the read
command (falling edge of the clock on the ACK bit prior to
RTC data output) into a separate latch to avoid time changes
during the read operation. The clock continues to run.
Alarms occurring during a read are unaffected by the read
operation.
Writing to the Real Time Clock
The time and date may be set by writing to the RTC
registers. RTC Register should be written ONLY with Page
Write. To avoid changing the current time by an uncompleted
write operation, write to the all 8 bytes in one write operation.
When writing the RTC registers, the new time value is
loaded into a separate buffer at the falling edge of the clock
during the Acknowledge. This new RTC value is loaded into
the RTC Register by a stop bit at the end of a valid write
sequence. An invalid write operation aborts the time update
procedure and the contents of the buffer are discarded. After
a valid write operation, the RTC will reflect the newly loaded
data beginning with the next “one second” clock cycle after
the stop bit is written. The RTC continues to update the time
while an RTC register write is in progress and the RTC
continues to run during any non-volatile write sequences.
Accuracy of the Real Time Clock
The accuracy of the Real Time Clock depends on the
accuracy of the quartz crystal that is used as the time base
for the RTC. Since the resonant frequency of a crystal is
temperature dependent, the RTC performance will also be
dependent upon temperature. The frequency deviation of
the crystal is a function of the turnover temperature of the
crystal from the crystal’s nominal frequency. For example, a
>20ppm frequency deviation translates into an accuracy of
>1 minute per month. These parameters are available from
the crystal manufacturer. Intersil’s RTC family provides onchip crystal compensation networks to adjust
load-capacitance to tune oscillator frequency from -34ppm to
+80ppm when using a 12.5pF load crystal. For more detailed
information see “Application Section” on page 22.
10
CCR Access
The CCR is divided into 5 sections. These are:
1. Alarm 0 (8 bytes; non-volatile)
2. Alarm 1 (8 bytes; non-volatile)
3. Control (5 bytes; non-volatile)
4. Real Time Clock (8 bytes; volatile)
5. Status (1 byte; volatile)
Each register is read and written through buffers. The
non-volatile portion (or the counter portion of the RTC) is
updated only if RWEL is set and only after a valid write
operation and stop bit. A sequential read or page write
operation provides access to the contents of only one
section of the CCR per operation. Access to another section
requires a new operation. A read or write can begin at any
address in the CCR.
It is not necessary to set the RWEL bit prior to writing the
status register. Section 5 (status register) supports a single
byte read or write only. Continued reads or writes from this
section terminates the operation.
The state of the CCR can be read by performing a random
read at any address in the CCR at any time. This returns the
contents of that register location. Additional registers are
read by performing a sequential read. The read instruction
latches all Clock registers into a buffer, so an update of the
clock does not change the time being read. A sequential
read of the CCR will not result in the output of data from the
memory array. At the end of a read, the master supplies a
stop condition to end the operation and free the bus. After a
read of the CCR, the address remains at the previous
address +1 so the user can execute a current address read
of the CCR and continue reading the next Register.
Real Time Clock Registers (Volatile)
SC, MN, HR, DT, MO, YR: Clock/Calendar Registers
These registers depict BCD representations of the time. As
such, SC (Seconds) and MN (Minutes) range from 00 to 59,
HR (Hour) is 1 to 12 with an AM or PM indicator (H21 bit) or
FN8232.8
August 12, 2010
ISL12027, ISL12027A
0 to 23 (with MIL = 1), DT (Date) is 1 to 31, MO (Month) is 1
to 12, YR (Year) is 0 to 99.
DW: Day of the Week Register
This register provides a Day of the Week status and uses
three bits DY2 to DY0 to represent the seven days of the
week. The counter advances in the cycle 0-1-2-3-4-5-6-0-12-… The assignment of a numerical value to a specific day
of the week is arbitrary and may be decided by the system
software designer. The default value is defined as ‘0’.
Y2K: Year 2000 Register
Can have value 19 or 20. As of the date of the introduction of
this device, there would be no real use for the value 19 in a
true real time clock, however.
24 Hour Time
If the MIL bit of the HR register is 1, the RTC uses a 24-hour
format. If the MIL bit is 0, the RTC uses a 12-hour format and
H21 bit functions as an AM/PM indicator with a ‘1’,
representing PM. The clock defaults to standard time with
H21 = 0.
Leap Years
Leap years add the day February 29 and are defined as
those years that are divisible by 4.
Status Register (SR) (Volatile)
The Status Register is located in the CCR memory map at
address 003Fh. This is a volatile register only and is used to
control the WEL and RWEL write enable latches, read power
status and two alarm bits. This register is separate from both
the array and the Clock/Control Registers (CCR).
TABLE 1. STATUS REGISTER (SR)
ADDR
7
6
003Fh
BAT
AL1
Default
0
0
5
4
AL0 OSCF
0
0
3
2
1
0
0
RWEL
WEL
RTCF
0
0
0
1
BAT: Battery Supply
This bit set to “1” indicates that the device is operating from
VBAT, not VDD. It is a read-only bit and is set/reset by
hardware (ISL12027 internally). Once the device begins
operating from VDD, the device sets this bit to “0”.
AL1, AL0: Alarm Bits
These bits announce if either alarm 0 or alarm 1 match the
real time clock. If there is a match, the respective bit is set to
‘1’. The falling edge of the last data bit in a SR Read
operation resets the flags. Note: Only the AL bits that are set
when an SR read starts will be reset. An alarm bit that is set
by an alarm occurring during an SR read operation will
remain set after the read operation is complete.
11
OSCF: Oscillator Fail Indicator
This bit is set to “1” if the oscillator is not operating, or is
operating but has clock jitter which does not affect the
accuracy of RTC counting. The bit is set to “0” if the oscillator
is functioning and does not have clock jitter. This bit is read
only, and is set/reset by hardware.
RWEL: Register Write Enable Latch
This bit is a volatile latch that powers up in the LOW
(disabled) state. The RWEL bit must be set to “1” prior to any
writes to the Clock/Control Registers. Writes to RWEL bit do
not cause a non-volatile write cycle, so the device is ready
for the next operation immediately after the stop condition. A
write to the CCR requires both the RWEL and WEL bits to be
set in a specific sequence.
WEL: Write Enable Latch
The WEL bit controls the access to the CCR during a write
operation. This bit is a volatile latch that powers up in the
LOW (disabled) state. While the WEL bit is LOW, writes to
the CCR address will be ignored, although acknowledgment
is still issued. The WEL bit is set by writing a “1” to the WEL
bit and zeroes to the other bits of the Status Register. Once
set, WEL remains set until either reset to 0 (by writing a “0”
to the WEL bit and zeroes to the other bits of the Status
Register) or until the part powers up again. Writes to WEL bit
do not cause a non-volatile write cycle, so the device is
ready for the next operation immediately after the stop
condition.
RTCF: Real Time Clock Fail Bit
This bit is set to a “1” after a total power failure. This is a read
only bit that is set by hardware (ISL12027 internally) when
the device powers up after having lost all power to the device
(both VDD and VBAT go to 0V). The bit is set regardless of
whether VDD or VBAT is applied first. The loss of only one of
the supplies does not set the RTCF bit to “1”. On power up
after a total power failure, all registers are set to their default
states and the clock will not increment until at least one byte
is written to the clock register. The first valid write to the RTC
section after a complete power failure resets the RTCF bit to
“0” (writing one byte is sufficient).
Unused Bits:
Bit 3 in the SR is not used, but must be zero. The Data Byte
output during a SR read will contain a zero in this bit
location.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
REG
NAME
7
6
Status
SR
BAT
AL1
AL0
RTC
(SRAM)
Y2K
0
0
Y2K21
ADDR.
TYPE
003F
0037
5
4
3
2
1
0
OSCF
0
RWEL
WEL
RTCF
Y2K20
Y2K13
0
0
Y2K10
RANG
E
19/20
ISL12027A
DEFAULT
BIT
ISL12027
DEFAULT
TABLE 2. CLOCK/CONTROL MEMORY MAP
01h
01h
20h
20h
DW
0
0
0
0
0
DY2
DY1
DY0
0-6
00h
00h
0035
YR
Y23
Y22
Y21
Y20
Y13
Y12
Y11
Y10
0-99
00h
00h
0034
MO
0
0
0
G20
G13
G12
G11
G10
1-12
00h
00h
0033
DT
0
0
D21
D20
D13
D12
D11
D10
1-31
01h
01h
0032
HR
MIL
0
H21
H20
H13
H12
H11
H10
0-23
00h
00h
0031
MN
0
M22
M21
M20
M13
M12
M11
M10
0-59
00h
00h
0-59
0036
0030
0014
0013
0012
Control
(EEPROM
)
SC
0
S22
S21
S20
S13
S12
S11
S10
PWR
SBIB
BSW
0
0
0
VTS2
VTS1
VTS0
00h
00h
4Xh
0Xh
DTR
0
0
0
0
0
DTR2
DTR1
DTR0
00h
00h
ATR
0
0
ATR5
ATR4
ATR3
ATR2
ATR1
ATR0
00h
00h
0011
INT
IM
AL1E
AL0E
0
0
0
0
0
00h
00h
0010
BL
BP2
BP1
BP0
WD1
WD0
0
0
0
18h
18h
Y2K1
0
0
0
0
A1Y2K10
19/20
20h
20h
DWA1
EDW1
0
DY2
DY1
DY0
0-6
00h
00h
000F
000E
000D
Alarm1
(EEPROM
)
000C
YRA1
MOA1
A1Y2K21 A1Y2K20 A1Y2K13
0
0
0
Unused - Default = RTC Year value (No EEPROM) - Future expansion
EMO1
0
0
A1G20
A1G13
A1G12
A1G11
A1G10
1-12
00h
00h
000B
DTA1
EDT1
0
A1D21
A1D20
A1D13
A1D12
A1D11
A1D10
1-31
00h
00h
000A
HRA1
EHR1
0
A1H21
A1H20
A1H13
A1H12
A1H11
A1H10
0-23
00h
00h
0009
MNA1
EMN1
A1M22
A1M21
A1M20
A1M13
A1M12
A1M11
A1M10
0-59
00h
00h
0008
SCA1
ESC1
A1S22
A1S21
A1S20
A1S13
A1S12
A1S11
A1S10
0-59
00h
00h
Y2K0
0
0
0
0
A0Y2K10
19/20
20h
20h
DWA0
EDW0
0
DY2
DY1
DY0
0-6
00h
00h
0007
0006
0005
0004
Alarm0
(EEPROM
)
YRA0
MOA0
A0Y2K21 A0Y2K20 A0Y2K13
0
0
0
Unused - Default = RTC Year value (No EEPROM) - Future expansion
EMO0
0
0
A0G20
A0G13
A0G12
A0G11
A0G10
1-12
00h
00h
0003
DTA0
EDT0
0
A0D21
A0D20
A0D13
A0D12
A0D11
A0D10
1-31
00h
00h
0002
HRA0
EHR0
0
A0H21
A0H20
A0H13
A0H12
A0H11
A0H10
0-23
00h
00h
0001
MNA0
EMN0
A0M22
A0M21
A0M20
A0M13
A0M12
A0M11
A0M10
0-59
00h
00h
0000
SCA0
ESC0
A0S22
A0S21
A0S20
A0S13
A0S12
A0S11
A0S10
0-59
00h
00h
NOTE: (Shaded cells indicate that NO other value is to be written to that bit. X indicates the bits are set according to the product variation, see device
“Ordering Information” on page 2).
12
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Alarm Registers (Non-Volatile)
Alarm0 and Alarm1
The alarm register bytes are set up identical to the RTC
register bytes, except that the MSB of each byte functions as
an enable bit (enable = “1”). These enable bits specify which
alarm registers (seconds, minutes, etc.) are used to make
the comparison. Note that there is no alarm byte for year.
Six analog trimming bits, ATR0 to ATR5, are provided in
order to adjust the on-chip load capacitance value for
frequency compensation of the RTC. Each bit has a different
weight for capacitance adjustment. For example, using a
Citizen CFS-206 crystal with different ATR bit combinations
provides an estimated ppm adjustment range from -34ppm
to +80ppm to the nominal frequency compensation.
The alarm function works as a comparison between the
alarm registers and the RTC registers. As the RTC
advances, the alarm will be triggered once a match occurs
between the alarm registers and the RTC registers. Any one
alarm register, multiple registers, or all registers can be
enabled for a match. See “Device Operation” on page 14
and “Application Section” on page 22 for more information.
X1
CX1
CRYSTAL
OSCILLATOR
X2
CX2
Control Registers (Non-Volatile)
The Control Bits and Registers described in the following
section are non-volatile.
BL Register
BP2, BP1, BP0 - Block Protect Bits
The Block Protect Bits, BP2, BP1 and BP0, determine which
blocks of the array are write protected. A write to a protected
block of memory is ignored. The block protect bits will
prevent write operations to one of eight segments of the
array. The partitions are described in Table 3.
The effective on-chip series load capacitance, CLOAD,
ranges from 4.5pF to 20.25pF with a mid-scale value of
12.5pF (default). CLOAD is changed via two digitally
controlled capacitors, CX1 and CX2, connected from the X1
and X2 pins to ground (see Figure 12). The value of CX1 and
CX2 is given Equation 1:
C X = ( 16 ⋅ b5 + 8 ⋅ b4 + 4 ⋅ b3 + 2 ⋅ b2 + 1 ⋅ b1 + 0.5 ⋅ b0 + 9 )pF
(EQ. 1)
The effective series load capacitance is the combination of
CX1 and CX2:
TABLE 3.
BP1
BP0
ARRAY LOCK
BP2
PROTECTED ADDRESSES
ISL12027
0
0
0
None (Default)
None
0
0
1
180h – 1FFh
Upper 1/4
0
1
0
100h – 1FFh
Upper 1/2
0
1
1
000h – 1FFh
Full Array
1
0
0
000h – 03Fh
First 4 Pages
1
0
1
000h – 07Fh
First 8 Pages
1
1
0
000h – 0FFh
First 16 Pages
1
1
1
000h – 1FFh
Full Array
Oscillator Compensation Registers
There are two trimming options.
• ATR. Analog Trimming Register
• DTR. Digital Trimming Register
These registers are non-volatile. The combination of analog
and digital trimming can give up to -64 to +110ppm of total
adjustment.
ATR Register - ATR5, ATR4, ATR3, ATR2, ATR1,
ATR0: Analog Trimming Register
13
FIGURE 12. DIAGRAM OF ATR
1
1
1
⎛ ---------- + -----------⎞
⎝C
C ⎠
C LOAD = ----------------------------------X1
(EQ. 2)
X2
16 ⋅ b5 + 8 ⋅ b4 + 4 ⋅ b3 + 2 ⋅ b2 + 1 ⋅ b1 + 0.5 ⋅ b0 + 9
C LOAD = ⎛ -----------------------------------------------------------------------------------------------------------------------------⎞ pF
⎝
⎠
2
For example, CLOAD(ATR = 00000) = 12.5pF,
CLOAD(ATR = 100000) = 4.5pF, and
CLOAD(ATR = 011111) = 20.25pF. The entire range for the
series combination of load capacitance goes from 4.5pF to
20.25pF in 0.25pF steps. Note that these are typical values.
DTR Register - DTR2, DTR1, DTR0: Digital
Trimming Register
The digital trimming Bits DTR2, DTR1 and DTR0 adjust the
number of counts per second and average the ppm error to
achieve better accuracy.
DTR2 is a sign bit. DTR2 = 0 means frequency
compensation is >0. DTR2 = 1 means frequency
compensation is <0.
DTR1 and DTR0 are scale bits. DTR1 gives 10ppm
adjustment and DTR0 gives 20ppm adjustment.
A range from -30ppm to +30ppm can be represented by
using the three DTR bits.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
TABLE 4. DIGITAL TRIMMING REGISTERS
DTR REGISTER
TABLE 5.
VTS2
VTS1
VTS0
VRESET
0
0
0
4.64V
DTR2
DTR1
DTR0
ESTIMATED FREQUENCY
PPM
0
0
0
0
0
0
1
4.38V
0
1
0
+10
0
1
0
3.09V
0
1
1
2.92V
1
0
0
2.63V
0
0
1
+20
0
1
1
+30
1
0
0
0
1
1
0
-10
1
0
1
-20
1
1
1
-30
In battery mode, the RESET signal output is asserted LOW
when the VDD voltage supply has dipped below the VRESET
threshold, but the RESET signal output will not return HIGH
until the device is back to VDD mode even the VDD voltage is
above VRESET threshold.
PWR Register: SBIB, BSW, VTS2, VTS1, VTS0
Device Operation
SBIB: Serial Bus Interface (Enable)
Writing to the Clock/Control Registers
The serial bus can be disabled in battery backup mode by
setting this bit to “1”. This will minimize power drain on the
battery. The Serial Interface can be enabled in battery
backup mode by setting this bit to “0” (default is “0”). See
“Power Control Operation” on page 15 and “RESET” on
page 9.
Changing any of the bits of the clock/control registers
requires the following steps:
BSW: Power Control Bit
The Power Control bit, BSW, determines the conditions for
switching between VDD and Backup Battery. There are two
options:
Option 1. Standard: Set “BSW = 0” (default for ISL12027A)
Option 2. Legacy /Default Mode: Set “BSW = 1” (default
for ISL12027)
See “Power Control Operation” on page 15 for more details.
Also see “I2C Communications During Battery Backup and
LVR Operation” on page 24 for important details.
VTS2, VTS1, VTS0: VRESET Select Bits
The ISL12027 is shipped with a default VDD threshold
(VRESET) per the “Ordering Information” table on page 2.
This register is a non-volatile with no protection, therefore
any writes to this location can change the default value from
that marked on the package. If not changed with a nonvolatile write, this value will not change over normal
operating and storage conditions. However, ISL12027 has
four (4) additional selectable levels to fit the customers
application. Levels are: 4.64V (default), 4.38V, 3.09V, 2.92V
and 2.63V. The VRESET selection is via 3 bits (VTS2, VTS1
and VTS0). See Table 5.
Care should be taken when changing the VRESET select bits.
If the VRESET voltage selected is higher than VDD, then the
device will go into RESET and unless VDD is increased, the
device will no longer be able to communicate using the I2C
bus.
14
1. Write a 02h to the Status Register to set the Write Enable
Latch (WEL). This is a volatile operation, so there is no
delay after the write. (Operation preceded by a start and
ended with a stop).
2. Write a 06h to the Status Register to set both the Register
Write Enable Latch (RWEL) and the WEL bit. This is also
a volatile cycle. The zeros in the data byte are required.
(Operation proceeded by a start and ended with a stop).
Write all 8 bytes to the RTC registers, or one byte to the SR,
or one to five bytes to the control registers. This sequence
starts with a start bit, requires a slave byte of “11011110” and
an address within the CCR and is terminated by a stop bit. A
write to the EEPROM registers in the CCR will initiate a
non-volatile write cycle and will take up to 20ms to complete.
A write to the RTC registers (SRAM) will require much
shorter cycle time (t = tBUF). Writes to undefined areas have
no effect. The RWEL bit is reset by the completion of a write
to the CCR, so the sequence must be repeated to again
initiate another change to the CCR contents. If the sequence
is not completed for any reason (by sending an incorrect
number of bits or sending a start instead of a stop, for
example) the RWEL bit is not reset and the device remains
in an active mode. Writing all zeros to the status register
resets both the WEL and RWEL bits. A read operation
occurring between any of the previous operations will not
interrupt the register write operation.
Alarm Operation
Since the alarm works as a comparison between the alarm
registers and the RTC registers, it is ideal for notifying a host
processor of a particular time event and trigger some action as
a result. The host can be notified by polling the Status Register
(SR) Alarm bits. These two volatile bits (AL1 for Alarm 1 and
AL0 for Alarm 0), indicate if an alarm has happened. The AL1
and AL0 bits in the status register are reset by the falling edge
of the eighth clock of status register read.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
There are two alarm operation modes: Single Event and
periodic Interrupt Mode:
1. Single Event Mode is enabled by setting the AL0E or
AL1E bit to “1”, the IM bit to “0”, and disabling the
frequency output. This mode permits a one-time match
between the alarm registers and the RTC registers. Once
this match occurs, the AL0 or AL1 bit is set to “1”. Once
the AL0 or AL1 bit is read, this will automatically reset it.
Both Alarm registers can be set at the same time to
trigger alarms. Polling the SR will reveal which alarm has
been set.
2. Interrupt Mode (or “Pulsed Interrupt Mode” or PIM) is
enabled by setting the AL0E or AL1E bit to “1” the IM bit
to “1”, and disabling the frequency output. If both AL0E
and AL1E bits are set to 1, then only the AL0E PIM alarm
will function (AL0E overrides AL1E). This means that
once the interrupt mode alarm is set, it will continue to
alarm for each occurring match of the alarm and present
time. This mode is convenient for hourly or daily
hardware interrupts in microcontroller applications such
as security cameras or utility meter reading. Interrupt
Mode CANNOT be used for general periodic alarms,
however, since a specific time period cannot be
programmed for interrupt, only matches to a specific time
of day. The interrupt mode is only stopped by disabling
the IM bit or the Alarm Enable bits.
Writing to the Alarm Registers
The Alarm Registers are non-volatile but require special
attention to insure a proper non-volatile write takes place.
Specifically, byte writes to individual registers are good for all
but registers 0006h and 0000Eh, which are the DWA0 and
DWA1 registers, respectively. Those registers will require a
special page write for non-volatile storage. The
recommended page write sequences are as follows:
1. 16-byte page writes: The best way to write or update the
Alarm Registers is to perform a 16-byte write beginning at
address 0001h (MNA0) and wrapping around and ending
at address 0000h (SCA0). This will insure that
non-volatile storage takes place. This means that the
code must be designed so that the Alarm0 data is written
starting with Minutes register, and then all the Alarm1
data, with the last byte being the Alarm0 Seconds (the
page ends at the Alarm1 Y2k register and then wraps
around to address 0000h).
Alternatively, the 16-byte page write could start with
address 0009h, wrap around and finish with address
0008h. Note that any page write ending at address
0007h or 000Fh (the highest byte in each Alarm) will not
trigger a non-volatile write, so wrapping around or
overlapping to the following Alarm's Seconds register is
advised.
2. Other non-volatile writes: It is possible to do writes of
less than an entire page, but the final byte must always
be addresses 0000h through 0004h or 0008h though
000Ch to trigger a non-volatile write. Writing to those
blocks of 5 bytes sequentially, or individually, will trigger a
15
non-volatile write. If the DWA0 or DWA1 registers need to
be set, then enough bytes will need to be written to
overlap with the other Alarm register and trigger the
non-volatile write. For Example, if the DWA0 register is
being set, then the code can start with a multiple byte
write beginning at address 0006h, and then write 3 bytes
ending with the SCA1 register as follows:
Addr
0006h
0007h
0008h
Name
DWA0
Y2K0
SCA1
If the Alarm1 is used, SCA1 would need to have the correct
data written.
Power Control Operation
The power control circuit accepts a VDD and a VBAT input.
Many types of batteries can be used with Intersil RTC
products. For example, 3.0V or 3.6V Lithium batteries are
appropriate, and battery sizes are available that can power
an Intersil RTC device for up to 10 years. Another option is
to use a SuperCap for applications where VDD is interrupted
for up to a month. See “Application Section” on page 22 for
more information.
There are two options for setting the change-over conditions
from VDD to Battery backup mode. The BSW bit in the PWR
register controls this operation.
Option 1 - Standard Mode: Set “BSW = 0” (default for
ISL12027A)
Option 2 - Legacy/Default Mode: Set “BSW = 1” (default for
ISL12027)
TABLE 6. VBAT TRIP POINT WITH DIFFERENT BSW SETTING
BSW BIT
VBAT TRIP
POINT (V)
POWER CONTROL SETTING
0
2.2
Standard Mode (ISL12027A)
1
0
Legacy Mode (ISL12027)
Note that applications that have VBAT > VDD will require
theISL12027A (standard mode) for proper start-up. The I2C
bus may or may not be operational during battery backup;
that function is controlled by the SBIB bit. That operation is
covered after the power control section.
OPTION 1 - STANDARD POWER CONTROL MODE
(ISL12027A)
In the Standard mode, the supply will switch over to the
battery when VDD drops below VTRIP or VBAT, whichever is
lower. In this mode, accidental operation from the battery is
prevented since the battery backup input will only be used
when the VDD supply is shut off.
To select Option 1, BSW bit in the Power Register must be
set to “BSW = 0”. A description of power switchover follows.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Standard Mode Power Switchover
• Normal Operating Mode (VDD) to Battery Backup Mode
(VBAT)
To transition from the VDD to VBAT mode, both of the
following conditions must be met:
• Condition 1:
VDD < VBAT - VBATHYS
where VBATHYS ≈ 50mV
changing from Normal to Legacy Mode. If the VBAT voltage is
higher than VDD, then the device will enter battery back up
and unless the battery is disconnected or the voltage
decreases, the device will no longer operate from VDD. If that
is the situation on initial power-up, then I2C communication
may not be possible. For these applications, the ISL12027A
should be used.
To select the Option 2, BSW bit in the Power Register must
be set to “BSW = 1”.
• Condition 2:
VDD < VTRIP
where VTRIP ≈ 2.2V
• Normal Mode (VDD) to Battery Backup Mode (VBAT)
• Battery Backup Mode (VBAT) to Normal Mode (VDD)
The ISL12027 device will switch from the VBAT to VDD mode
when one of the following conditions occurs:
• Condition 1:
VDD > VBAT + VBATHYS
where VBATHYS ≈ 50mV
To transition from the VDD to VBAT mode, the following
conditions must be met:
VDD < VBAT - VBATHYS
• Battery Backup Mode (VBAT) to Normal Mode (VDD)
The device will switch from the VBAT to VDD mode when the
following condition occurs:
• Condition 2:
VDD > VTRIP + VTRIPHYS
where VTRIPHYS ≈ 30mV
VDD > VBAT +VBATHYS
There are two discrete situations that are possible when
using Standard Mode: VBAT < VTRIP and VBAT > VTRIP.
These two power control situations are illustrated in
Figures 13 and 14.
The Legacy Mode power control conditions are illustrated in
Figure 15.
VDD
VOLTAGE
ON
VBAT
IN
OFF
BATTERY BACKUP
MODE
VDD
FIGURE 15. BATTERY SWITCHOVER IN LEGACY MODE
VTRIP
2.2V
VBAT
1.8V
VBAT + VBATHYS
VBAT - VBATHYS
FIGURE 13. BATTERY SWITCHOVER WHEN VBAT < VTRIP
VBAT
3.0V
VTRIP
2.2V
VTRIP
VTRIP + VTRIPHYS
FIGURE 14. BATTERY SWITCHOVER WHEN VBAT > VTRIP
OPTION 2 -LEGACY POWER CONTROL MODE
(ISL12027 DEFAULT)
The Legacy Mode follows conditions set in X1226 products.
In this mode, switching from VDD to VBAT is simply done by
comparing the voltages and the device operates from
whichever is the higher voltage. Care should be taken when
16
Application of power to the ISL12027 activates a Power On
Reset Circuit that pulls the RESET pin active. This signal
provides several benefits.
• It prevents the system microprocessor from starting to
operate with insufficient voltage.
• It prevents the processor from operating prior to
stabilization of the oscillator.
BATTERY BACKUP
MODE
VDD
Power On Reset
• It allows time for an FPGA to download its configuration
prior to initialization of the circuit.
• It prevents communication to the EEPROM, greatly
reducing the likelihood of data corruption on power-up.
When VDD exceeds the device VRESET threshold value for
typically 250ms the circuit releases RESET, allowing the
system to begin operation. Recommended slew rate is
between 0.2V/ms and 50V/ms.
NOTE: If the VBAT voltage drops below the data sheet
minimum of 1.8V and the VDD power cycles to 0V then back
to VDD voltage, then the RESET output may stay low and the
I2C communications will not operate. The VBAT and VDD
power will need to be cycled to 0V together to allow normal
operation again.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Watchdog Timer Operation
The Watchdog timer timeout period is selectable. By writing
a value to WD1 and WD0, the Watchdog timer can be set to
3 different time out periods or off. When the Watchdog timer
is set to off, the watchdog circuit is configured for low power
operation (see Table 7).
Serial Communication
Interface Conventions
The device supports the I2C Protocol.
TABLE 7.
WD1
WD0
DURATION
1
1
disabled
1
0
250ms
0
1
750ms
0
0
1.75s
Watchdog Timer Restart
The Watchdog Timer is started by a falling edge of SDA
when the SCL line is high (START condition). The start
signal restarts the watchdog timer counter, resetting the
period of the counter back to the maximum. If another
START fails to be detected prior to the Watchdog timer
expiration, then the RESET pin becomes active for one reset
time out period. In the event that the start signal occurs
during a reset time out period, the start will have no effect.
When using a single START to refresh Watchdog timer, a
STOP condition should be followed to reset the device back
to stand-by mode.(see Figure 3).
In battery mode, the Watchdog timer function is disabled.
Low Voltage Reset (LVR) Operation
When a power failure occurs, a voltage comparator
compares the level of the VDD line versus a preset threshold
voltage (VRESET), then generates a RESET pulse if it is
below VRESET. The reset pulse will timeout 250ms after the
VDD line rises above VRESET. If the VDD remains below
VRESET, then the RESET output will remain asserted low.
Power-up and power-down waveforms are shown in
Figure 4. The LVR circuit is to be designed so the RESET
signal is valid down to VDD = 1.0V.
When the LVR signal is active, unless the part has been
switched into the battery mode, the completion of an
in-progress non-volatile write cycle is unaffected, allowing a
non-volatile write to continue as long as possible (down to
the Reset Valid Voltage). The LVR signal, when active, will
terminate any in-progress communications to the device and
prevents new commands from disrupting any current write
operations. See “I2C Communications During Battery
Backup and LVR Operation” on page 24.
In battery mode, the RESET signal output is asserted LOW
when the VDD voltage supply has dipped below the VRESET
17
threshold. The RESET signal output will not return HIGH
until the device is back to VDD mode even if the VDD
voltage is above VRESET threshold.
Clock and Data
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are reserved for
indicating start and stop conditions. (see Figure 16).
Start Condition
All commands are preceded by the start condition, which is a
HIGH to LOW transition of SDA when SCL is HIGH. The
device continuously monitors the SDA and SCL lines for the
start condition and will not respond to any command until
this condition has been met. (see Figure 17).
Stop Condition
All communications must be terminated by a stop condition,
which is a LOW to HIGH transition of SDA when SCL is
HIGH. The stop condition is also used to place the device
into the Standby power mode after a read sequence. A stop
condition can only be issued after the transmitting device
has released the bus. (see Figure 17).
Acknowledge
Acknowledge is a software convention used to indicate
successful data transfer. The transmitting device, either
master or slave, will release the bus after transmitting 8-bits.
During the ninth clock cycle, the receiver will pull the SDA
line LOW to acknowledge that it received the 8-bits of data.
Refer to Figure 18.
The device will respond with an acknowledge after
recognition of a start condition and if the correct Device
Identifier and Select bits are contained in the Slave Address
Byte. If a write operation is selected, the device will respond
with an acknowledge after the receipt of each subsequent
8-bit word. The device will not acknowledge if the slave
address byte is incorrect.
In the read mode, the device will transmit 8-bits of data,
release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no stop
condition is generated by the master, the device will continue
to transmit data. The device will terminate further data
transmissions if an acknowledge is not detected. The master
must then issue a stop condition to return the device to
Standby mode and place the device into a known state.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
SCL
SDA
DATA STABLE
DATA CHANGE
DATA STABLE
FIGURE 16. VALID DATA CHANGES ON THE SDA BUS
SCL
SDA
START
STOP
FIGURE 17. VALID START AND STOP CONDITIONS
SCL FROM
MASTER
1
8
9
DATA OUTPUT
FROM TRANSMITTER
DATA OUTPUT
FROM RECEIVER
START
ACKNOWLEDGE
FIGURE 18. ACKNOWLEDGE RESPONSE FROM RECEIVER
DEVICE IDENTIFIER
ARRAY
CCR
1
1
SLAVE ADDRESS BYTE
BYTE 0
0
1
1
0
0
1
1
1
1
R/W
0
0
0
0
0
0
0
A8
WORD ADDRESS 1
BYTE 1
A7
A6
A5
A4
A3
A2
A1
A0
WORD ADDRESS 0
BYTE 2
D7
D6
D5
D4
D3
D2
D1
D0
DATA BYTE
BYTE 3
FIGURE 19. SLAVE ADDRESS, WORD ADDRESS, AND DATA BYTES (64 BYTE PAGES)
18
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Device Addressing
Following a start condition, the master must output a Slave
Address Byte. The first 4 bits of the Slave Address Byte
specify access to either the EEPROM array or to the CCR.
Slave bits ‘1010’ access the EEPROM array. Slave bits
‘1101’ access the CCR.
When shipped from the factory, EEPROM array is
UNDEFINED, and should be programmed by the customer
to a known state.
Bit 3 through Bit 1 of the slave byte specify the device select
bits. These are set to ‘111’.
The last bit of the Slave Address Byte defines the operation
to be performed. When this R/W bit is a one, then a read
operation is selected. A zero selects a write operation. Refer
to Figure 19.
After loading the entire Slave Address Byte from the SDA
bus, the ISL12027 compares the device identifier and device
select bits with ‘1010111’ or ‘1101111’. Upon a correct
compare, the device outputs an acknowledge on the SDA
line.
Following the Slave Byte is a 2 byte word address. The word
address is either supplied by the master device or obtained
from an internal counter. On power-up the internal address
counter is set to address 0h, so a current address read of the
EEPROM array starts at address 0. When required, as part
of a random read, the master must supply the 2 Word
Address Bytes as shown in Figure 19.
In a random read operation, the slave byte in the “dummy
write” portion must match the slave byte in the “read”
section. That is if the random read is from the array the slave
byte must be 1010111x in both instances. Similarly, for a
random read of the Clock/Control Registers, the slave byte
must be 1101111x in both places.
Write Operations
Byte Write
For a write operation, the device requires the Slave Address
Byte and the Word Address Bytes. This gives the master
access to any one of the words in the array or CCR. (Note:
Prior to writing to the CCR, the master must write a 02h, then
06h to the status register in two preceding operations to
enable the write operation. See “Writing to the Clock/Control
Registers”). Upon receipt of each address byte, the
ISL12027 responds with an acknowledge. After receiving
both address bytes the ISL12027 awaits the 8-bits of data.
After receiving the 8-data bits, the ISL12027 again responds
with an acknowledge. The master then terminates the
transfer by generating a stop condition. The ISL12027 then
begins an internal write cycle of the data to the non-volatile
memory. During the internal write cycle, the device inputs
are disabled, so the device will not respond to any requests
19
from the master. The SDA output is at high impedance (see
Figure 20).
A write to a protected block of memory is ignored, but will still
receive an acknowledge. At the end of the write command,
the ISL12027 will not initiate an internal write cycle, and will
continue to ACK commands.
Byte writes to all of the non-volatile registers are allowed,
except the DWAn registers which require multiple byte writes
or page writes to trigger non-volatile writes. See “Device
Operation” on page 14 for more information.
Page Write
The ISL12027 has a page write operation. It is initiated in the
same manner as the byte write operation; but instead of
terminating the write cycle after the first data byte is
transferred, the master can transmit up to 15 more bytes to
the memory array and up to 7 more bytes to the clock/control
registers. The RTC registers require a page write (8 bytes),
individual register writes are not allowed. (Note: Prior to
writing to the CCR, the master must write a 02h, then 06h to
the status register in two preceding operations to enable the
write operation. See “Writing to the Clock/Control Registers”
on page 14”)
After the receipt of each byte, the ISL12027 responds with
an acknowledge, and the address is internally incremented
by one. The address pointer remains at the last address byte
written. When the counter reaches the end of the page, it
“rolls over” and goes back to the first address on the same
page. This means that the master can write 16 bytes to a
memory array page or 8 bytes to a CCR section starting at
any location on that page. For example, if the master begins
writing at location 10 of the memory and loads 15 bytes, then
the first 6 bytes are written to addresses 10 through 15, and
the last 6 bytes are written to columns 0 through 5.
Afterwards, the address counter would point to location 6 on
the page that was just written. If the master supplies more
than the maximum bytes in a page, then the previously
loaded data is over-written by the new data, one byte at a
time. Refer to Figure 21.The master terminates the Data
Byte loading by issuing a stop condition, which causes the
ISL12027 to begin the non-volatile write cycle. As with the
byte write operation, all inputs are disabled until completion
of the internal write cycle. Refer to Figure 22 for the address,
acknowledge and data transfer sequence.
Stops and Write Modes
Stop conditions that terminate write operations must be sent
by the master after sending at least 1 full data byte and it’s
associated ACK signal. If a stop is issued in the middle of a
data byte, or before 1 full data byte + ACK is sent, then the
ISL12027 resets itself without performing the write. The
contents of the array are not affected.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
S
T
A
R
T
SIGNALS FROM
THE MASTER
SDA BUS
WORD
ADDRESS 1
SLAVE
ADDRESS
1
S
T
O
P
DATA
0000000
1 110
A
C
K
SIGNALS FROM
THE SLAVE
WORD
ADDRESS 0
A
C
K
A
C
K
A
C
K
FIGURE 20. BYTE WRITE SEQUENCE
6 BYTES
6 BYTES
ADDRESS = 5
ADDRESS
ADDRESS
ADDRESS POINTER ENDS
AT ADDR = 5
10
15
FIGURE 21. WRITING 12 BYTES TO A 16-BYTE MEMORY PAGE STARTING AT ADDRESS 10
SIGNALS FROM
THE MASTER
SDA BUS
1 ≤ n ≤ 16 FOR EEPROM ARRAY
1 ≤ n ≤ 8 FOR CCR
S
T
A
R
T
WORD
ADDRESS 1
SLAVE
ADDRESS
1
DATA
(1)
S
T
O
P
DATA
(n)
0 0 0 00 0 0
1 1 1 0
A
C
K
SIGNALS FROM
THE SLAVE
WORD
ADDRESS 0
A
C
K
A
C
K
A
C
K
FIGURE 22. PAGE WRITE SEQUENCE
Acknowledge Polling
Current Address Read
Disabling of the inputs during non-volatile write cycles can
be used to take advantage of the typical 5ms write cycle
time. Once the stop condition is issued to indicate the end of
the master’s byte load operation, the ISL12027 initiates the
internal non-volatile write cycle. Acknowledge polling can
begin immediately. To do this, the master issues a start
condition followed by the Memory Array Slave Address Byte
for a write or read operation (AEh or AFh). If the ISL12027 is
still busy with the non-volatile write cycle, then no ACK will
be returned. When the ISL12027 has completed the write
operation, an ACK is returned and the host can proceed with
the read or write operation. Refer to the flow chart in
Figure 24. Note: Do not use the CCR Slave byte (DEh or
DFh) for Acknowledge Polling.
Internally the ISL12027 contains an address counter that
maintains the address of the last word read incremented by
one. Therefore, if the last read was to address n, the next
read operation would access data from address n + 1. On
power-up, the 16 bit address is initialized to 0h. In this way, a
current address read immediately after the power on reset
can download the entire contents of memory starting at the
first location. Upon receipt of the Slave Address Byte with
the R/W bit set to one, the ISL12027 issues an
acknowledge, then transmits 8 data bits. The master
terminates the read operation by not responding with an
acknowledge during the ninth clock and issuing a stop
condition. Refer to Figure 23 for the address, acknowledge,
and data transfer sequence.
Read Operations
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read operation,
the master must either issue a stop condition during the
ninth cycle or hold SDA HIGH during the ninth clock cycle
and then issue a stop condition.
There are three basic read operations: Current Address
Read, Random Read and Sequential Read.
20
FN8232.8
August 12, 2010
ISL12027, ISL12027A
SIGNALS FROM
THE MASTER
SDA BUS
Random Read
S
T
A
R
T
S
T
O
P
SLAVE
ADDRESS
1
Random read operations allow the master to access any
location in the ISL12027. Prior to issuing the Slave Address
Byte with the R/W bit set to zero, the master must first
perform a “dummy” write operation.
1 1 1 1
A
C
K
SIGNALS FROM
THE SLAVE
DATA
FIGURE 23. CURRENT ADDRESS READ SEQUENCE
BYTE LOAD
COMPLETED BY
ISSUING STOP.
ENTER ACK POLLING
ISSUE START
ISSUE MEMORY ARRAY SLAVE
ADDRESS BYTE
AFH (READ) OR AEH (WRITE)
ISSUE STOP
NO
ACK
RETURNED?
The master issues the start condition and the slave address
byte, receives an acknowledge, then issues the word
address bytes. After acknowledging receipt of each word
address byte, the master immediately issues another start
condition and the slave address byte with the R/W bit set to
one. This is followed by an acknowledge from the device and
then by the 8 bit data word. The master terminates the read
operation by not responding with an acknowledge and then
issuing a stop condition. Refer to Figure 25 for the address,
acknowledge, and data transfer sequence.
In a similar operation called “Set Current Address,” the
device sets the address if a stop is issued instead of the
second start shown in Figure 25. The ISL12027 then goes
into standby mode after the stop and all bus activity will be
ignored until a start is detected. This operation loads the new
address into the address counter. The next Current Address
Read operation will read from the newly loaded address.
This operation could be useful if the master knows the next
address it needs to read, but is not ready for the data.
Sequential Read
YES
NO
NON-VOLATILE WRITE
CYCLE COMPLETE. CONTINUE
COMMAND SEQUENCE?
ISSUE STOP
YES
CONTINUE
NORMAL READ OR
WRITE COMMAND
SEQUENCE
PROCEED
FIGURE 24. ACKNOWLEDGE POLLING SEQUENCE
21
Sequential reads can be initiated as either a current address
read or random address read. The first data byte is
transmitted as with the other modes; however, the master
now responds with an acknowledge, indicating it requires
additional data. The device continues to output data for each
acknowledge received. The master terminates the read
operation by not responding with an acknowledge and then
issuing a stop condition.
The data output is sequential, with the data from address n
followed by the data from address n + 1. The address
counter for read operations increments through all page and
column addresses, allowing the entire memory contents to
be serially read during one operation. At the end of the
address space the counter “rolls over” to the start of the
address space and the ISL12027 continues to output data
for each acknowledge received. Refer to Figure 26 for the
acknowledge and data transfer sequence.
FN8232.8
August 12, 2010
ISL12027, ISL12027A
S
T
A
R
T
SIGNALS FROM
THE MASTER
SDA BUS
SLAVE
ADDRESS
1
WORD
ADDRESS 0
WORD
ADDRESS 1
00 00000
1 1 1 0
S
T
O
P
SLAVE
ADDRESS
1
A
C
K
A
C
K
SIGNALS FROM
THE SLAVE
S
T
A
R
T
1 1 11
A
C
K
A
C
K
DATA
FIGURE 25. RANDOM ADDRESS READ SEQUENCE
SIGNALS
FROM
THE MASTER
SDA BUS
SLAVE
ADDRESS
A
C
K
S
T
O
P
A
C
K
A
C
K
1
SIGNALS FROM
THE SLAVE
A
C
K
DATA
(1)
DATA
(2)
DATA
(n - 1)
DATA
(n)
(n IS ANY INTEGER GREATER THAN 1)
FIGURE 26. SEQUENTIAL READ SEQUENCE
Application Section
Crystal Oscillator and Temperature Compensation
Intersil has now integrated the oscillator compensation
circuity on-chip, to eliminate the need for external
components and adjust for crystal drift over-temperature and
enable very high accuracy time keeping (<5ppm drift).
The Intersil RTC family uses an oscillator circuit with on-chip
crystal compensation network, including adjustable
load-capacitance. The only external component required is
the crystal. The compensation network is optimized for
operation with certain crystal parameters which are common
in many of the surface mount or tuning-fork crystals available
today. Table 8 summarizes these parameters.
Table 9 contains some crystal manufacturers and part numbers
that meet the requirements for the Intersil RTC products.
The turnover temperature in Table 8 describes the
temperature where the apex of the of the drift vs temperature
curve occurs. This curve is parabolic with the drift increasing
as (T - T0)2. For an Epson MC-405 device, for example, the
turnover temperature is typically +25°C, and a peak drift of
>110ppm occurs at the temperature extremes of -40°C and
+85°C. It is possible to address this variable drift by adjusting
the load capacitance of the crystal, which will result in
predictable change to the crystal frequency. The Intersil RTC
family allows this adjustment over temperature since the
devices include on-chip load capacitor trimming. This control
is handled by the Analog Trimming Register, or ATR, which
has 6-bits of control. The load capacitance range covered by
the ATR circuit is approximately 3.25pF to 18.75pF, in
22
0.25pF increments. Note that actual capacitance would also
include about 2pF of package related capacitance. In-circuit
tests with commercially available crystals demonstrate that
this range of capacitance allows frequency control from
+116ppm to -37ppm, using a 12.5pF load crystal.
In addition to the analog compensation afforded by the
adjustable load capacitance, a digital compensation feature
is available for the Intersil RTC family. There are 3-bits
known as the Digital Trimming Register or DTR, and they
operate by adding or skipping pulses in the clock signal. The
range provided is ±30ppm in increments of 10ppm. The
default setting is 0ppm. The DTR control can be used for
coarse adjustments of frequency drift over-temperature or
for crystal initial accuracy correction.
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,
and 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
FN8232.8
August 12, 2010
ISL12027, ISL12027A
circuit and produce double clocking or mis-clocking, 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 ISL12027 or ISL12026 devices.
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 VDD pin of the chip is mandatory,
with a solid connection to ground (see Figure 27).
TABLE 8. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL RTC’S
PARAMETER
MIN
Frequency
TYP
MAX
32.768
Frequency Tolerance
Turnover Temperature
20
Operating Temperature Range
-40
Parallel Load Capacitance
25
UNITS
kHz
±100
ppm
30
°C
85
°C
12.5
Equivalent Series Resistance
NOTES
Down to 20ppm if desired
Typically the value used for most crystals
pF
50
kΩ
For best oscillator performance
TABLE 9. CRYSTAL MANUFACTURERS
MANUFACTURER
PART NUMBER
TEMP RANGE (°C)
+25°C FREQUENCY TOLERANCE (ppm)
Citizen
CM201, CM202, CM200S
-40 to +85
±20
Epson
MC-405, MC-406
-40 to +85
±20
Raltron
RSM-200S-A or B
-40 to +85
±20
SaRonix
32S12A or B
-40 to +85
±20
Ecliptek
ECPSM29T-32.768K
-10 to +60
±20
ECS
ECX-306/ECX-306I
-10 to +60
±20
Fox
FSM-327
-40 to +85
±20
XTAL1
32.768kHZ
U1
ISL12027
R1
C1
01µF
10k
FIGURE 27. SUGGESTED LAYOUT FOR INTERSIL RTC IN SO-8
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 start-up should definitely occur in less than 5s.
When testing RTC circuits, the most common impulse is to
23
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 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. Alternatively the
frequency can be 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.
Backup Battery Operation
Many types of batteries can be used with the Intersil RTC
products. 3.0V or 3.6V Lithium batteries are appropriate, and
sizes are available that can power a Intersil RTC device for
up to 10 years. Another option is to use a supercapacitor for
applications where VDD may disappear intermittently for
short periods of time. Depending on the value of
FN8232.8
August 12, 2010
ISL12027, ISL12027A
supercapacitor used, backup time can last from a few days
to two weeks (with >1F). A simple silicon or Schottky barrier
diode can be used in series with VDD to charge the
supercapacitor, which is connected to the VBAT pin. Try to
use Schottky diodes with very low leakages, <1µA desirable.
Do not use the diode to charge a battery (especially lithium
batteries!).
Note that whether a battery or supercap is used, if the VBAT
voltage drops below the data sheet minimum of 1.8V and the
VDD power cycles to 0V then back to VDD voltage, then the
RESET output may stay low and the I2C communications will
not operate. The VBAT and VDD power will need to be cycled
to 0V together to allow normal operation again.
There are two possible modes for battery backup operation,
Standard and Legacy mode. In Standard mode, there are no
operational concerns when switching over to battery backup
since all other devices functions are disabled. Battery drain
is minimal in Standard mode, and return to Normal VDD
powered operations predictable. In Legacy modes the VBAT
pin can power the chip if the voltage is above VDD and
VTRIP. This makes it possible to generate alarms and
communicate with the device under battery backup, but the
supply current drain is much higher than the Standard mode
and backup time is reduced. During initial power-up, the
default mode is the Legacy mode.
2.7V TO 5.5V
VDD
VBAT
SUPERCAPACITOR
VSS
FIGURE 28. SUPERCAPACITOR CHARGING CIRCUIT
24
I2C Communications During Battery Backup and
LVR Operation
Operation in Battery Backup mode and LVR is affected by
the BSW and SBIB bits as described earlier. These bits allow
flexible operation of the serial bus and EEPROM in battery
backup mode, but certain operational details need to be
clear before utilizing the different modes. The most
significant detail is that once VDD goes below VRESET, then
I2C communications cease regardless of whether the device
is programmed for I2C operation in battery backup mode.
Table 10 describes 4 different modes possible with using the
BSW and SBIB bits, and how they are affect LVR and battery
backup operation.
• Mode A - In this mode, selection bits indicate a low VDD
switchover combined with I2C operation in battery backup
mode. In actuality the VDD will go below VRESET before
switching to battery backup, which will disable I2C
ANYTIME the device goes into battery backup mode.
Regardless of the battery voltage, the I2C will work down
to the VRESET voltage (see Figure 29).
• Mode B - In this mode, the selection bits indicate
switchover to battery backup at VDD<VBAT, and I2C
communications in battery backup. In order to
communicate in battery backup mode, the VRESET voltage
must be less than the VBAT voltage AND VDD must be
greater than VRESET. Also, pull-ups on the I2C bus pins
must go to VBAT to communicate. This mode is the same
as the normal operating mode of the X1228 device.
• Mode C - In this mode, the selection bits indicate a low
VDD switchover combined with no communications in
battery backup. Operation is actually identical to Mode A
with I2C communications down to VDD = VRESET, then no
communications (see Figure 28).
• Mode D - In this mode, the selection bits indicate
switchover to battery backup at VDD < VBAT, and no I2C
communications in battery backup. This mode is unique in
that there is I2C communication as long as VDD is higher
than VRESET or VBAT, whichever is greater. This mode is
the safest for guaranteeing I2C communications only when
there is a Valid VDD (see Figure 29).
FN8232.8
August 12, 2010
ISL12027, ISL12027A
.
TABLE 10. I2C, LV RESET, AND BATTERY BACKUP OPERATION SUMMARY (Shaded Row is same as X12028 operation)
MODE
SBIB
BIT
I2C ACTIVE IN
BATTERY
BACKUP?
VBAT
SWITCHOVER
VOLTAGE
BSW
BIT
EE PROM WRITE/
READ IN BATTERY
BACKUP?
FREQ/IRQ
ACTIVE?
NOTES
2
A
0
0
Standard Mode,
VTRIP = 2.2V
typ
Default for
ISL12027A
NO
NO
N/A
Operation of I C bus down to VDD =VRESET,
then below that no communications. Battery
switchover at VTRIP.
B
(X12028
mode)
0
1
Legacy Mode,
VDD < VBAT
Default for
ISL12027
YES, only if
VBAT > VRESET
YES
Yes
Operation of I2C bus into battery backup
mode, but only for
VBAT > VDD > VRESET.
Bus must have pull-ups to VBAT. No
non-volatile writes with VBAT > VDD
C
1
0
Standard Mode,
VTRIP = 2.2V
typ
NO
NO
YES
Operation of I2C bus down to VDD = VRESET,
then below that no communications. Battery
switchover at VTRIP.
D
1
1
Legacy Mode,
VDD < VBAT
NO
NO
YES
Operation of I2C busdown to VRESET or
VBAT, whichever is higher.
.
VBAT (3.0V)
VRESET (2.63V)
VDD
VTRIP
(2.2V)
tPURST
RESET
I2C Bus Active
(VDD POWER, VBAT NOT CONNECTED)
IBAT
(BATTERY BACKUP MODE)
FIGURE 29. EXAMPLE RESET OPERATION IN MODE A OR C
VDD
VBAT (3.0V)
VRESET (2.63V)
VTRIP
(2.2V)
tPURST
RESET
I2C BUS ACTIVE
IBAT
(BATTERY BACKUP MODE)
FIGURE 30. RESET OPERATION IN MODE D
25
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Alarm Operation Examples
Following are examples of both Single Event and periodic
Interrupt Mode alarms.
After these registers are set, an alarm will be generated when
the RTC advances to exactly 11:30am on January 1 (after
seconds changes from 59 to 00) by setting the AL0 bit in the
status register to “1”.
EXAMPLE 1
EXAMPLE 2
Alarm 0 set with single interrupt (IM=”0”)
A single alarm will occur on January 1 at 11:30am.
A. Set Alarm 0 registers as follows:
ALARM0
REGISTER 7
Pulsed interrupt once per minute (IM = ”1”)
Interrupts at one minute intervals when the seconds register
is at 30s.
A. Set Alarm 0 registers as follows:
BIT
6
5
4
3
2
1
0
HEX
DESCRIPTION
BIT
ALARM0
REGISTER 7 6 5 4 3 2 1 0 HEX
SCA0
0
0
0
0
0
0
0
0
00h Seconds disabled
MNA0
1
0
1
1
0
0
0
0
B0h Minutes set to 30,
enabled
SCA0
1 0 1 1 0 0 0 0 B0h Seconds set to 30,
enabled
HRA0
1
0
0
1
0
0
0
1
91h Hours set to 11,
enabled
MNA0
0 0 0 0 0 0 0 0 00h Minutes disabled
DTA0
1
0
0
0
0
0
0
1
81h Date set to 1,
enabled
HRA0
0 0 0 0 0 0 0 0 00h Hours disabled
DTA0
0 0 0 0 0 0 0 0 00h Date disabled
MOA0
0 0 0 0 0 0 0 0 00h Month disabled
DWA0
0 0 0 0 0 0 0 0 00h Day of week disabled
MOA0
1
0
0
0
0
0
0
1
81h Month set to 1,
enabled
DWA0
0
0
0
0
0
0
0
0
00h Day of week
disabled
B. Also the AL0E bit must be set as follows:
CONTROL
REGISTER 7
INT
0
6
5
4
3
2
1
0
HEX
0
1
0
0
0
0
0
x0h
B. Set the Interrupt register as follows:
BIT
CONTROL
REGISTER 7 6 5 4 3 2 1 0 HEX
BIT
DESCRIPTION
DESCRIPTION
INT
DESCRIPTION
1 0 1 0 0 0 0 0 x0h Enable Alarm and Int
Mode
Enable Alarm
Note that the status register AL0 bit will be set each time the
alarm is triggered, but does not need to be read or cleared.
26
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Package Outline Drawing
M8.173
8 LEAD THIN SHRINK SMALL OUTLINE PACKAGE (TSSOP)
Rev 2, 01/10
A
2
4
3.0 ±0.5
SEE DETAIL "X"
5
8
6.40
CL
4.40 ±0.10
3
4
PIN 1
ID MARK
0.20 C BA
1
4
0.09-0.20
B
0.65
TOP VIEW
END VIEW
1.00 REF
0.05
H
C
0.90 +0.15/-0.10
1.20 MAX
SEATING
PLANE
0.25 +0.05/-0.06
0.10 C
0.10
GAUGE
PLANE
0.25
6
CBA
0°-8°
0.05 MIN
0.15 MAX
0.60 ±0.15
DETAIL "X"
SIDE VIEW
(1.45)
NOTES:
1. Dimensions are in millimeters.
Dimensions in ( ) for Reference Only.
(5.65)
PACKAGE BODY
OUTLINE
2. Dimension does not include mold flash, protrusions or
gate burrs. Mold flash, protrusions or gate burrs shall
not exceed 0.15 per side.
3. Dimension does not include interlead flash or protrusion.
Interlead flash or protrusion shall not exceed 0.15 per side.
4. Dimensions are measured at datum plane H.
5. Dimensioning and tolerancing per ASME Y14.5M-1994.
(0.35 TYP)
(0.65 TYP)
TYPICAL RECOMMENDED LAND PATTERN
27
6. Dimension on lead width does not include dambar protrusion.
Allowable protrusion shall be 0.08 mm total in excess of
dimension at maximum material condition. Minimum space
between protrusion and adjacent lead is 0.07mm.
7. Conforms to JEDEC MO-153, variation AC. Issue E
FN8232.8
August 12, 2010
ISL12027, ISL12027A
Small Outline Plastic Packages (SOIC)
M8.15 (JEDEC MS-012-AA ISSUE C)
N
8 LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE
INDEX
AREA
H
0.25(0.010) M
B M
INCHES
E
SYMBOL
-B-
1
2
3
L
SEATING PLANE
-A-
A
D
h x 45°
-C-
e
A1
B
0.25(0.010) M
C
0.10(0.004)
C A M
MIN
MAX
MIN
MAX
NOTES
A
0.0532
0.0688
1.35
1.75
-
A1
0.0040
0.0098
0.10
0.25
-
B
0.013
0.020
0.33
0.51
9
C
0.0075
0.0098
0.19
0.25
-
D
0.1890
0.1968
4.80
5.00
3
E
0.1497
0.1574
3.80
4.00
4
e
α
B S
0.050 BSC
1.27 BSC
-
H
0.2284
0.2440
5.80
6.20
-
h
0.0099
0.0196
0.25
0.50
5
L
0.016
0.050
0.40
1.27
6
N
α
NOTES:
MILLIMETERS
8
0°
8
8°
0°
7
8°
1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of
Publication Number 95.
Rev. 1 6/05
2. Dimensioning and tolerancing per ANSI Y14.5M-1982.
3. Dimension “D” does not include mold flash, protrusions or gate burrs.
Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006
inch) per side.
4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per
side.
5. The chamfer on the body is optional. If it is not present, a visual index
feature must be located within the crosshatched area.
6. “L” is the length of terminal for soldering to a substrate.
7. “N” is the number of terminal positions.
8. Terminal numbers are shown for reference only.
9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater
above the seating plane, shall not exceed a maximum value of
0.61mm (0.024 inch).
10. Controlling dimension: MILLIMETER. Converted inch dimensions
are not necessarily exact.
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.
Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com
28
FN8232.8
August 12, 2010