AB18XX Series
Real Time Clock Module
Date of Issue: Sept. 10
th
, 2012
Page (1) of (13)
3.0 x 3.0 mm
Abracon Drawing #
ESD Sensitive
Revision #: Initial Release
AB18XX Features
Sub-threshold Power Optimized Technology by Ambiq Micro
Ultra-low supply current:
-
<15 nA with RC oscillator
-
<20 nA with RC oscillator and autocalibration
-
<55 nA with crystal oscillator
Baseline timekeeping features:
-
32 KHz crystal oscillator with integrated load
capacitor/resistor
-
Counters for hundredths, seconds, minutes, hours, date,
month, year, century, and weekday
-
Alarm capability on all counters
-
Programmable output clock generation (32 kHz to 1/year)
-
Countdown timer with repeat function
-
Automatic leap year calculation
Advanced timekeeping features:
-
Integrated power optimized RC oscillator
-
Advanced crystal calibration to ± 2 ppm
-
Advanced RC calibration to ± 16 ppm
-
Automatic calibration of RC oscillator to crystal oscillator
-
Watchdog timer with hardware reset
-
Up to 256 bytes of general purpose RAM
Power management features:
-
Integrated <1Ω power switch for off-chip components
such as a host MCU
-
System sleep manager for managing host processor
wake/sleep states
-
External interrupt monitor
-
External reset signal monitor
-
Reset output generator
-
Automatic switchover to VBAT
-
Supercapacitor trickle charger with programmable
charging current
-
Programmable brown out detection
-
Programmable analog voltage comparator
I
2
C (up to 400 kHz) or SPI (up to 2 MHz) serial interface
-
Supports 3-wire and 4-wire SPI
Operating Voltage 1.7-3.6 V
Clock and RAM retention voltage 1.5-3.6 V
Operating temperature –40 to 85 °C
All inputs include Schmitt triggers
3 mm x 3 mm QFN-16 package
Applications
Smart cards
Wireless sensors and tags
Medical electronics
Utility meters
Data loggers
Appliances
Handsets
Consumer electronics
Description
The Abracon Corporation AB18XX Real Time Clock with
Power Management family provides a groundbreaking
combination of ultra-low power coupled with a highly
sophisticated feature set. With power requirements significantly
lower than any other industry RTC (as low as 15nA), these are
the first semiconductor products based on Abracon Corporation’s
innovative SPOT (Sub-threshold Power Optimized Technology
by Ambiq Micro) CMOS platform. The AB18XX includes on-
chip oscillators to provide minimum power consumption, full
RTC functions including battery backup and programmable
counters and alarms for timer and watchdog functions, and either
an I
2
C or SPI serial interface for communication with a host
controller. An integrated power switch and a sophisticated
system sleep manager with counter, timer, alarm, and interrupt
capabilities allows the AB18XX to be used as a supervisory
component in a host microcontroller-based system.
AB18XX Series
Real Time Clock Module
Date of Issue: Sept. 10
th
, 2012
Page (1) of (13)
3.0 x 3.0 mm
Abracon Drawing #
ESD Sensitive
Revision #: Initial Release
1.
Family Summary
The AB18XX family consists of several members. All devices are supplied in a standard 3 mm x 3 mm QFN-16 package.
Members of the software and pin compatible AB08XX RTC family are also listed.
Part #
AB1801
AB1803
AB1804
AB1805
AB1811
AB1813
AB1814
AB1815
Baseline
Timekeeping
Number
XT
of GP
Osc
Outputs
2
2
4
4
2
2
3
3
Advanced Timekeeping
RC
Osc
Calib/
Auto-calib
Watch-
dog
RA
M
(B)
0
64
256
256
0
64
256
256
VBAT
Switch
Power Management
Reset
Mgmt
Ext
Int
Power
Switch and
Sleep FSM
Interface
I
2
C
I
2
C
I
2
C
I
2
C
SPI
SPI
SPI
SPI
Software and Pin Compatible AB08XX Family Components
AB0801
AB0803
AB0804
AB0805
AB0811
AB0813
AB0814
AB0815
2
2
4
4
2
2
3
3
0
64
256
256
0
64
256
256
I2C
I2C
I2C
I2C
SPI
SPI
SPI
SPI
AB18XX Series
Real Time Clock Module
Date of Issue: Sept. 10
th
, 2012
Page (2) of (13)
3.0 x 3.0 mm
Abracon Drawing #
ESD Sensitive
Revision #: Initial Release
2.
AB18XX Functional Description
VCC VBAT
100ths
Seconds
Minutes
Hours
Days
Weekdays
Months
Years
Alarms
Timer
WDT
Control
RC Osc
Divider
RAM
nCE
SDI
SCL
SDA/O
Power
Control
I2C/SPI
Interface
Analog
Compare
Calibration Engine
XO
XT Osc
Divider
XI
WDI
EXTI
nEXTR
Reset
Int/Clock
FOUT/nIRQ
PSW/nIRQ2
nTIRQ
CLKOUT/nIRQ3
nRST
VSS
The AB18XX serves as a companion part for host processors including microcontrollers, radios, and digital signal
processors. It tracks time as in a typical RTC product and additionally provides unique power management functionality that
makes it ideal for highly energy-constrained applications. To support such operation, the AB18XX includes 3 distinct feature
groups: 1) baseline timekeeping features, 2) advanced timekeeping features, and 3) power management features. Functions
from each feature group may be controlled via memory mapped registers. These registers are accessed using either an I
2
C
serial interface (e.g., in the AB1805) or a SPI serial interface (e.g., in the AB1815). Each feature group is described briefly
below.
The baseline timekeeping feature group supports the standard 32 kHz crystal (XT) oscillation mode for maximum frequency
accuracy with an ultra-low current draw of 55 nA. An extended calibration mode enables low jitter digital calibration to an
accuracy of ±2 ppm over a range of -614 ppm to +244 ppm. The baseline timekeeping feature group also includes a standard
set of counters monitoring hundredths of a second up through centuries. A complement of countdown timers and alarms may
additionally be set to initiate interrupts or resets on several of the outputs.
The advanced timekeeping feature group supports two additional oscillation modes: 1) RC oscillator mode, and 2) auto-
calibration mode. At only 15 nA, the temperature-compensated ±10% RC oscillator mode provides an even lower current
draw than the XT oscillator for applications with reduced frequency accuracy requirements. A proprietary calibration
algorithm allows the AB18XX to digitally tune the RC oscillator frequency with accuracy as low as ±2 ppm at a given
temperature and very low calibration jitter. In autocalibration mode, the RC oscillator is used as the primary oscillation
source and is periodically calibrated against the XT oscillator. Autocalibration may be executed every autocalibration period
(ACP) of 8.5 minutes or 17 minutes and may also be initiated via software. This mode enables average current draw of only
20 nA with frequency accuracy similar to the XT oscillator. The advanced timekeeping feature group also includes a rich set
of input and output configuration options that enables the monitoring of external interrupts (e.g., pushbutton signals), the
generation of clock outputs, and watchdog timer functionality.
AB18XX Series
Real Time Clock Module
Date of Issue: Sept. 10
th
, 2012
Page (3) of (13)
3.0 x 3.0 mm
Abracon Drawing #
ESD Sensitive
Revision #: Initial Release
Power management features built into the AB18XX enable it to operate as a backup device in both line-powered and battery-
powered systems. An integrated power control module automatically detects when main power (VCC) falls below a
digitally-selectable threshold and switches to backup power (VBAT). Up to 256B of ultra-low leakage RAM enable the
storage of key parameters when operating on backup power.
The AB18XX is the first RTC to incorporate a number of more advanced power management features. In particular, the
AB18XX includes a finite state machine (integrated with the Power Control block) that can control a host processor as it
transitions between sleep/reset states and active states. Digital outputs can be configured to control the reset signal or
interrupt input of the host controller with digitally-tunable timing. The AB18XX additionally integrates a power switch with
<1 Ω impedance that can be used to cut off ground current on the host microcontroller and reduce sleep current to <1 nA.
The AB18XX parts can wake-up a sleeping system using internally generated timing interrupts or externally generated
interrupts generated by digital inputs (e.g., using a pushbutton). The aforementioned functionality enables users to
seamlessly power down host processors, leaving only the energy-efficient AB18XX chip awake. The AB18XX also includes
digitally-tunable voltage monitoring for brown-out detection and power-on reset.
3.
AB18XX Example Applications
The AB18XX enables a variety of system implementations in which the AB18XX can control power usage by other elements
in the system. This is typically used when the entire system is powered from a battery and minimizing total power usage is
critical. The backup RAM in the AB18XX can be used to hold key MCU parameters when it is powered down.
3.1
VSS Power Switched
In the recommended implementation, the internal power switch of the AB18XX is used to completely turn off the MCU
and/or other system elements. In this case the PSW/nIRQ2 output is configured to generate the Sleep function. Under
normal circumstances, the PSW/nIRQ2pin is pulled to VSS with less than 1 ohm of resistance, so that the MCU receives full
power. The MCU initiates a SLP operation, and when the AB18XX enters Sleep Mode the PSW/nIRQ2 pin is opened and
power is completely removed from the MCU. This results in significant additional power savings relative to the other
alternatives. A variety of interrupts, including alarms, timers and external interrupts created by a pushbutton as shown, may
be used to exit Sleep Mode and restore MCU power. The RAM of the AB18XX may be used to retain critical MCU
parameters.
R
EXTI
XO
AM18XX
AB18XX
VCC
FOUT/nIRQ
PSW/nIRQ2
VSS
I2C/SPI
IRQ
VSS
VCC
MCU
XI
AB18XX Series
Real Time Clock Module
Date of Issue: Sept. 10
th
, 2012
Page (4) of (13)
3.0 x 3.0 mm
Abracon Drawing #
ESD Sensitive
Revision #: Initial Release
3.2
VCC Power Switched
An external transistor switch T may also be used to turn off power to the MCU. This implementation allows switching
higher current and maintains a common ground. R can be on the order of megohms, so that negligible current is drawn when
the circuit is active and PSW/nIRQ2 is low.
T
R
AB18XX
AM18XX
VCC
I2C/SPI
IRQ
VSS
VCC
FOUT/nIRQ
PSW/nIRQ2
VSS
MCU
3.3
Reset Driven
In another implementation the AB18XX controls the system MCU using the reset function rather than switching power.
Since many MCUs use much less power when reset, this implementation can save system power in some cases.
VCC
AB18XX
AM18XX
nRST
VSS
I2C/SPI
RESET
VSS
VCC
MCU
3.4
Battery Backup
In many systems the main power supply is a battery, so the AB18XX can minimize its current draw by powering down the
MCU and other peripherals. This battery may be replaceable, and a supercapacitor charged via the AB18XX trickle charger
can maintain system time and key parameters when the main battery is removed.
VBAT
Backup
Supercap
XO
VCC
I2C/SPI
VCC
AB18XX
AM18XX
FOUT/nIRQ
PSW/nIRQ2
VSS
IRQ
MCU
Main
Battery
XI
VSS
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