DS1689/DS1693
3V/5V Serialized Real-Time Clocks
with NV RAM Control
www.maxim-ic.com
FEATURES
Incorporates Industry Standard DS1287 PC
Clock Plus Enhanced Features:
+3V or +5V Operation
64-Bit Silicon Serial Number
64-Bit Customer Specific ROM or
Additional Serial Number Available
Power Control Circuitry Supports System
Power-On from Date/Time Alarm or Key
Closure
Automatic Battery Backup and Write
Protection to External SRAM
Crystal Select Bit Allows RTC to Operate
with 6pF or 12.5pF Crystal
114 Bytes User NV RAM
Auxiliary Battery Input
RAM Clear Input
Century Register
32kHz Output for Power Management
32-Bit V
CC
Powered Elapsed Time Counter
32-Bit V
BAT
Powered Elapsed Time Counter
16-Bit Power Cycle Counter
Compatible with Existing BIOS for Original
DS1287 Functions
Available as IC (DS1689) or Stand-Alone
Module with Embedded Battery and Crystal
(DS1693)
Available in Industrial Temperature
Version
Timekeeping Algorithm Includes Leap Year
Compensation Valid Up to 2100
PIN CONFIGURATIONS
V
BAUX
N.C.
N.C.
RCLR
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
PWR
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CEI
CEO
V
CCI
V
CCO
SQW
N.C.
IRQ
PSEL
RD
N.C.
WR
ALE
CS
KS
V
BAUX
X1
X2
RCLR
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
PWR
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CEI
CEO
V
CCI
V
CCO
SQW
V
BAT
IRQ
PSEL
RD
GND
WR
ALE
CS
KS
DS1693
Encapsulated DIP
(740 Mils)
SO
(330 Mils)
ORDERING INFORMATION
PART
DS1689S
DS1689S+
DS1689SN
DS1689SN+
DS1689S/T&R
DS1689S+T&R
DS1689SN/T&R
DS1689SN+T&R
DS1693
TEMP RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
VOLTAGE (V)
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
3 to 5
PIN-PACKAGE
28 SO (0.330″)
28 SO (0.330″)
28 SO (0.330″)
28 SO (0.330″)
28 SO (0.330″)/Tape & Reel
28 SO (0.330″)/Tape & Reel
28 SO (0.330″)/Tape & Reel
28 SO (0.330″)/Tape & Reel
28 EDIP (0.740″)
TOP MARK*
DS1689S
DS1689S
DS1689S
DS1689S
DS1689S
DS1689S
DS1689S
DS1689S
DS1693
+
Denotes a lead-free/RoHS-compliant device.
*
A “+” anywhere on the top mark denotes a lead-free/RoHS-compliant device. An “N” denotes an industrial temperature device.
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DS1689
REV: 112105
DS1689/DS1693
PIN DESCRIPTION
PIN
SO
EDIP
NAME
FUNCTION
Auxiliary Battery Supply. Auxiliary battery input required for
kickstart and wake-up features. This input also supports
clock/calendar and External NV RAM if V
BAT
is at lower voltage or
is not present. A standard +3V lithium cell or other energy source
can be used. Battery voltage must be held between +2.5V and +3.7V
for proper operation. If V
BAUX
is not going to be used it should be
grounded and auxiliary battery enable bit bank 1, register 4BH,
should = 0.
Connections for Standard 32.768kHz Quartz Crystal. For greatest
accuracy, the DS1689 must be used with a crystal that has a
specified load capacitance of either 6pF or 12.5pF. The crystal select
(CS) bit in Extended Control Register 4B is used to select operation
with a 6pF or 12.5pF crystal. The crystal is attached directly to the
X1 and X2 pins. There is no need for external capacitors or resistors.
Note: X1 and X2 are very high-impedance nodes. It is recommended
that they and the crystal by guard-ringed with ground and that high-
frequency signals be kept away from the crystal area.
For more information on crystal selection and crystal layout
considerations, refer to
Application Note 58: Crystal Considerations
with Dallas Real Time Clocks.
The DS1689 can also be driven by an
external 32.768kHz oscillator. In this configuration, the X1 pin is
connected to the external oscillator signal and the X2 pin is floated.
Active-Low RAM Clear Input. If enabled by software, taking
RCLR
low will result in the clearing of the 114 bytes of user RAM. When
enabled,
RCLR
can be activated whether or not V
CC
is present.
Multiplexed Address/Data Bus. Multiplexed buses save pins because
address information and data information time-share the same signal
paths. The addresses are present during the first portion of the bus
cycle and the same pins and signal paths are used for data in the
second portion of the cycle. Address/data multiplexing does not slow
the access time of the DS1689 since the bus change from address to
data occurs during the internal RAM access time. Addresses must be
valid prior to the latter portion of ALE, at which time the
DS1689/DS1693 latches the address. Valid write data must be
present and held stable during the latter portion of the
WR
pulse. In a
read cycle, the DS1689/
DS1693 outputs 8 bits of data during the latter portion of the
RD
pulse. The read cycle is terminated and the bus returns to a high
impedance state as
RD
transitions high. The address/data bus also
serves as a bidirectional data path for the external extended RAM.
1
1
V
BAUX
2, 3
—
X1, X2
4
4
RCLR
5–12
5–12
AD0–AD7
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DS1689/DS1693
PIN
SO
EDIP
NAME
FUNCTION
Active-Low Power-On Interrupt Output. The
PWR
pin is intended
for use as an on/off control for the system power. With V
CC
voltage
removed from the DS1689/DS1693,
PWR
may be automatically
activated from a kickstart input via the
KS
pin or from a wake-up
interrupt. Once the system is powered on, the state of
PWR
can be
controlled via bits in the Dallas registers.
Ground. DC power is provided to the device on this pin.
Active-Low Kickstart Input. When V
CC
is removed from the
DS1689/DS1693, the system can be powered on in response to an
active low transition on the
KS
pin, as might be generated from a
key closure. V
BAUX
must be present and auxiliary battery enable bit
(ABE) must be set to 1 if the kickstart function is used, and the
KS
pin must be pulled up to the V
BAUX
supply. While V
CC
is applied, the
KS
pin can be used as an interrupt input.
Active-Low Chip Select Input. This signal must be asserted low
during a bus cycle for the RTC portion of the DS1689/DS1693 to be
accessed.
CS
must be kept in the active state during
RD
and
WR
timing. Bus cycles, which take place with ALE asserted but without
asserting,
CS
will latch addresses. However, no data transfer will
occur.
Address Strobe Input (Active High). A pulse on the address strobe
pin serves to demultiplex the bus. The falling edge of ALE causes
the RTC address to be latched within the DS1689/DS1693.
Active-Low Write Data Strobe. The
WR
signal is an active low
signal. The
WR
signal defines the time period during which data is
written to the addressed register.
Active-Low Read Data Strobe.
RD
identifies the time period when
the DS1689/DS1693 drives the bus with RTC read data. The
RD
signal is an enable signal for the output buffers of the clock.
+3V or +5V Power Select. When PSEL is logic 1, 5V operation is
selected. When PSEL is logic 0 or is floated, the device is in
autosense mode and determines the correct mode of operation based
on the voltage on V
CCI
.
Active-Low Interrupt Request Output (Open Drain). The
IRQ
pin is
an active-low output of the DS1689/DS1693 that can be tied to the
interrupt input of a processor. The
IRQ
output remains low as long
as the status bit causing the interrupt is present and the
corresponding interrupt-enable bit is set. To clear the
IRQ
pin, the
application software must clear all enabled flag bits contributing to
IRQ’s
active state. When no interrupt conditions are present, the
IRQ
level is in the high impedance state. Multiple interrupting devices
can be connected to an
IRQ
bus. The
IRQ
pin is an open-drain
output and requires an external pullup resistor.
Battery Input for Any Standard 3V Lithium Cell or Other Energy
Source. Battery voltage must be held between 2.5V and 3.7V for
proper operation.
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13
13
PWR
14, 19
14
GND
15
15
KS
16
16
CS
17
18
20
17
18
20
ALE
WR
RD
21
21
PSEL
22
22
IRQ
23
—
V
BAT
DS1689/DS1693
PIN
SO
EDIP
NAME
FUNCTION
Square-Wave Output. The SQW pin can output a signal from one of
13 taps provided by the 15 internal divider stages of the real time
clock. The frequency of the SQW pin can be changed by
programming Register A as shown in Table 2. The SQW signal can
be turned on and off using the SQWE bit in Register B. A 32kHz
SQW signal is output when SQWE = 1, the Enable 32kHz (E32K)
bit in extended register 04BH is logic 1, and V
CC
is above V
PF
. A
32kHz square wave is also available when V
CC
is less than V
PF
if
E32K = 1, ABE = 1, and voltage is applied to V
BAUX
.
External SRAM Power-Supply Output. This pin is internally
connected to V
CCI
when V
CCI
is within nominal limits. However,
during power fail, V
CCO
is internally connected to the V
BAT
or V
BAUX
(whichever is larger). For 5V operation, switchover from V
CCI
to the
backup supply occurs when V
CCI
drops below the larger of V
BAT
and
V
BAUX
. For 3V operation, switchover from V
CCI
to the backup supply
occurs at V
PF
if V
PF
is less than V
BAT
and V
BAUX
. If V
PF
is greater
than V
BAT
and V
BAUX
, the switch from V
CCI
to the backup supply
occurs when V
CCI
drops below the larger of V
BAT
and V
BAUX
.
+3V or +5V Main Supply. DC power is provided to the device on
these pins. 5V operation is selected when the PSEL pin is at logic 1.
If PSEL is floated or at logic 0, the device is in autosense mode and
determines the correct operating voltage based on the V
CCI
voltage
level.
Active-Low RAM Chip Enable Output. When power is valid,
CEO
will equal
CEI.
When power is not valid,
CEO
will be driven high
regardless of
CEI.
Active-Low RAM Chip Enable Input.
CEI
should be driven low to
enable the external RAM.
No Connection
24
24
SQW
25
25
V
CCO
26
26
V
CCI
27
28
—
27
28
2, 3,
19, 23
CEO
CEI
N.C.
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DS1689/DS1693
DETAILED DESCRIPTION
The DS1689/DS1693 are real-time clocks (RTCs) designed as successors to the industry standard
DS1285, DS1385, DS1485, and DS1585 PC real-time clocks. These devices provide the industry
standard DS1285 clock function with the new feature of either +3.0V or +5.0V operation and automatic
backup and write protection to an external SRAM. The DS1689 also incorporates a number of enhanced
features including a silicon serial number, power-on/off control circuitry, and 114 bytes of user NV
SRAM, power-on elapsed timer, and power-cycle counter.
Each DS1689/DS1693 is individually manufactured with a unique 64-bit serial number as well as an
additional 64-bit customer specific ROM or serial number. The serial number is programmed and tested
at Dallas to ensure that no two devices are alike. The serial number can be used to electronically identify
a system for purposes such as establishment of a network node address or for maintenance tracking.
Customers can reserve blocks of available numbers from Dallas Semiconductor.
The serialized RTCs also incorporate power control circuitry, which allows the system to be powered on
via an external stimulus, such as a keyboard or by a time and date (wake-up) alarm. The
PWR
output pin
can be triggered by one or either of these events, and can be used to turn on an external power supply.
The
PWR
pin is under software control, so that when a task is complete, the system power can then be
shut down.
The DS1689/DS1693 incorporate a power-on elapsed time counter, a power-on cycle counter, and a
battery powered continuous counter. These three counters provide valuable information for maintenance
and warranty requirements.
Automatic backup and write protection for an external SRAM is provided through the V
CCO
and
CEO
pins. The lithium energy source used to permanently power the real time clock is also used to retain RAM
data in the absence of V
CC
power through the V
CCO
pin. The chip enable output to RAM (CEO) is
controlled during power transients to prevent data corruption.
The DS1689 is a clock/calendar chip with the features described above. An external crystal and battery
are the only components required to maintain time-of-day and memory status in the absence of power.
The DS1693 incorporates the DS1689 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-
contained timekeeping module. The entire unit is fully tested at Dallas Semiconductor such that a
minimum of 10 years of timekeeping and data retention in the absence of V
CC
is guaranteed.
OPERATION
The block diagram in Figure 1 shows the pin connections with the major internal functions of the
DS1689/DS1693. The following paragraphs describe the function of each pin.
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