Dallas DS1543-70 64k nv timekeeping ram Datasheet

PRELIMINARY
DS1543
64k NV Timekeeping RAM
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
Integrated NV SRAM, real time clock, crystal,
power-fail control circuit and lithium energy
source
Clock registers are accessed identical to the
static RAM. These registers are resident in the
sixteen top RAM locations
Totally nonvolatile with over 10 years of
operation in the absence of power
Precision Power-On Reset
Programmable Watchdog Timer and RTC
Alarm
BCD coded year, month, date, day, hours,
minutes, and seconds with automatic leap year
compensation valid up to the year 2100
Battery voltage level indicator flag
Power-fail write protection allows for ±10%
Vcc power supply tolerance
Lithium energy source is electrically
disconnected to retain freshness until power is
applied for the first time
ORDERING INFORMATION
DS1543-XXX
*DS1543W-XXX
(5V)
-70
-100
70 ns access
100 ns access
(3.3V)
-120 120 ns access
-150 150 ns access
RST
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
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
VCC
WE
IRQ/FT
A8
A9
A11
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
28-Pin Encapsulated Package
(700 Mil Extended)
PIN DESCRIPTION
A0-A12
DQ0-DQ7
IRQ \FT
RST
CE
OE
WE
VCC
GND
NC
1 of 17
- Address Input
- Data Input/Outputs
- Interrupt, Frequency Test
Output (Open-Drain)
- Power-On Reset Output
(Open-Drain)
- Chip Enable
- Output Enable
- Write Enable
- Power Supply Input
- Ground
- No Connection
081000
DS1543
DESCRIPTION
The DS1543 is a full-function real-time clock/calendar (RTC) with a RTC alarm, watchdog timer, poweron reset, battery monitor, and 8k x 8 non-volatile static RAM. User access to all registers within the
DS1543 is accomplished with a bytewide interface as shown in Figure 1. The RTC registers contain year,
month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for day of month
and leap year are made automatically.
The RTC registers are double-buffered into an internal and external set. The user has direct access to the
external set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow
the user to access static data. Assuming the internal oscillator is turned on, the internal set of registers are
continuously updated; this occurs regardless of external registers settings to guarantee that accurate RTC
information is always maintained.
The DS1543 has interrupt ( IRQ /FT) and reset ( RST ) outputs which can be used to control CPU activity.
The IRQ /FT interrupt output can be used to generate an external interrupt when the RTC register values
match user programmed alarm values. The interrupt is always available while the device is powered from
the system supply and can be programmed to occur when in the battery backed state to serve as a system
wake-up. Either the IRQ /FT or RST outputs can also be used as a CPU watchdog timer, CPU activity is
monitored and an interrupt or reset output will be activated if the correct activity is not detected within
programmed limits. The DS1543 power-on reset can be used to detect a system power down or failure
and hold the CPU in a safe reset state until normal power returns and stabilizes; the RST output is used
for this function.
The DS1543 also contains its own power fail circuitry which automatically deselects the device when the
VCC supply enters an out of tolerance condition. This feature provides a high degree of data security
during unpredictable system operation brought on by low VCC levels.
PACKAGES
The DS1543 is available in two packages (28-pin DIP and 34-pin PowerCap module). The 28-pin DIP
style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin
PowerCap module board is designed with contacts for connection to a separate PowerCap (DS9034PCX)
that contains the crystal and battery. This design allows the Power-Cap to be mounted on top of the
DS1543P after the completion of the surface mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery due to the high temperatures required for solder
reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module board and
PowerCap are ordered separately and shipped in separate containers. The part number for the PowerCap
is DS9034PCX.
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DS1543
DS1543 BLOCK DIAGRAM Figure 1
DS1543 OPERATING MODES Table 1
VCC
In Tolerance
VBAT < VCC <
Tolerance
<VBAT
X
VIL
VIH
VIH
X
DQ0-DQ7
HIGH-Z
DIN
DOUT
HIGH-Z
HIGH-Z
A0-A12
X
AIN
AIN
AIN
X
MODE
DESELECT
WRITE
READ
READ
DESELECT
POWER
STANDBY
ACTIVE
ACTIVE
ACTIVE
CMOS STANDBY
X
HIGH-Z
X
DATA
RETENTION
BATTERY
CURRENT
CE
OE
WE
VIH
VIL
VIL
VIL
X
X
X
VIL
VIH
X
X
X
DATA READ MODE
The DS1543 is in the read mode whenever CE (chip enable) is low and WE (write enable) is high. The
device architecture allows ripple through access to any valid address location. Valid data will be
available at the DQ pins within tAA after the last address input is stable, providing that CE and OE access
times are satisfied. If CE or OE access times are not met, valid data will be available at the latter of chip
enable access (tCEA) or at output enable access time (tOEA). The state of the data input/output pins (DQ) is
controlled by CE and OE . If the outputs are activated before tAA, the data lines are driven to an
intermediate state until tAA. If the address inputs are changed while CE and OE remain valid, output data
will remain valid for output data hold time (tOH) but will then go indeterminate until the next address
access.
DATA WRITE MODE
The DS1543 is in the write mode whenever WE and CE are in their active state. The start of a write is
referenced to the latter occurring transition of WE or CE . The addresses must be held valid throughout
the cycle. CE and WE must return inactive for a minimum of tWR prior to the initiation of a subsequent
read or write cycle. Data in must be valid tDS prior to the end of the write and remain valid for tDH
afterward. In a typical application, the OE signal will be high during a write cycle. However, OE can be
3 of 17
DS1543
active provided that care is taken with the data bus to avoid bus contention. If OE is low prior to WE
transitioning low, the data bus can become active with read data defined by the address inputs. A low
transition on WE will then disable the outputs tWEZ after WE goes active.
DATA RETENTION MODE
The 5-volt device is fully accessible and data can be written and read only when VCC is greater than VPF.
However, when VCC is below the power-fail point VPF (point at which write protection occurs) the
internal clock registers and SRAM are blocked from any access. When VCC falls below the battery switch
point VSO (battery supply level), device power is switched from the VCC pin to the internal backup lithium
battery. RTC operation and SRAM data are maintained from the battery until VCC is returned to nominal
levels.
The 3.3-volt device is fully accessible and data can be written and read only when VCC is greater than
VPF. When VCC falls below VPF, access to the device is inhibited. If VPF is less than VBAT, the device
power is switched from VCC to the internal backup lithium battery when VCC drops below VPF If VPF is
greater than VBAT, the device power is switched from VCC to the internal backup lithium battery when
VCC drops below VBAT. RTC operation and SRAM data are maintained from the battery until VCC is
returned to nominal levels.
All control, data, and address signals must be powered down when VCC is powered down.
BATTERY LONGEVITY
The DS1543 has a lithium power source that is designed to provide energy for the clock activity, and
clock and RAM data retention when the VCC supply is not present. The capability of this internal power
supply is sufficient to power the DS1543 continuously for the life of the equipment in which it is
installed. For specification purposes, the life expectancy is 10 years at 25°C with the internal clock
oscillator running in the absence of VCC Each DS1543 is shipped from Dallas Semiconductor with its
lithium energy source disconnected, guaranteeing full energy capacity. When VCC is first applied at a
level greater than VPF the lithium energy source is enabled for battery backup operation. Actual life
expectancy of the DS1543 will be much longer than 10 years since no internal battery energy is
consumed when VCC is present. In fact, in most applications, the life expectancy of the DS1543 will be
approximately equal to the shelf life (expected useful life of the internal lithium battery with no load
attached) of the battery which may prove to be as long as 20 years.
INTERNAL BATTERY MONITOR
The DS15433 constantly monitors the battery voltage of the internal batter. The Battery Low Flag (BLF)
bit of the Flags register (B4 of 1FF0h) is not writable and should always be a 0 when read. If a 1 is ever
present, an exhausted lithium energy source is indicated and both the contents of the RTC and RAM are
questionable.
POWER-ON RESET
A temperature-compensated comparator circuit monitors the level of VCC When VCC falls to the power
fail trip point, the RST signal (open-drain) is pulled low. When VCC returns to nominal levels, the RST
signal continues to be pulled low for a period of 40 ms to 200 ms. The power-on reset function is
independent of the RTC oscillator and thus is operational whether or not the oscillator is enabled.
CLOCK OPERATIONS
Table 2 and the following paragraphs describe the operation of RTC, Alarm, and Watchdog functions.
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DS1543
DS1543 REGISTER MAP Table 2
ADDRESS
DATA
B7
B6
1FFFh
B5
B4
B3
10 Year
X
10 M
B2
B1
B0
FUNCTION/RANGE
YEAR
YEAR
00-99
MONTH
MONTH
01-12
DATE
DATE
01-31
DAY
01-07
HOUR
HOUR
00-23
MINUTES
MINUTES
00-59
SECONDS
00-59
1FFEh
X
X
1FFDh
X
X
1FFCh
X
FT
1FFBh
X
X
1FFAh
X
1FF9h
1FF8h
OSC
W
R
Y
Y
Y
Y
Y
Y
CONTROL
1FF7h
WDS
BMB4
BMB3
BMB2
BMB1
BMB0
RB1
RB0
WATCHDOG
1FF6h
AE
Y
ABE
Y
Y
Y
Y
Y
INTERRUPTS
1FF5h
AM4
Y
10 DATE
DATE
ALARM DATE
01-31
1FF4h
AM3
Y
10 HOURS
HOURS
ALARM HOURS
00-23
1FF3h
AM2
10 MINUTES
MINUTES
ALARM MINUTES
00-59
1FF2h
AM1
10 SECONDS
SECONDS
ALARM SECONDS
00-59
10 Date
X
X
X
10 HOUR
10 MINUTES
10 SECONDS
DAY
SECONDS
1FF1h
Y
Y
Y
Y
Y
Y
Y
Y
UNUSED
1FF0h
WF
AF
0
BLF
0
0
0
0
FLAGS
X = Unused, read/writable under Write and Read
bit control
FT = Frequency Test bit
OSC = Oscillator start/stop bit
W = Write bit
R = Read bit
WDS = Watchdog Steering bit
BMB0-BMB4 = Watchdog Multiplier bits
RB0-RB1 = Watchdog Resolution bits
AE = Alarm Flag Enable
Y = Unused, read/writable without Write and
bit control
ABE = Alarm in battery Back-up mode enable
AM1-AM4 = Alarm Mask bits
WF = Watchdog Flag
AF = Alarm Flag
0 = “0” and are read only
BLF = Battery Low Flag
CLOCK OSCILLATOR CONTROL
The Clock oscillator may be stopped at any time. To increase the shelf life of the backup lithium battery
source, the oscillator can be turned off to minimize current drain from the battery. The OSC bit is the
MSB of the seconds register (B7 of 1FF9h). Setting it to a 1 stops the oscillator, setting to a 0 starts the
oscillator. The DS1543 is shipped from Dallas Semiconductor with the clock oscillator turned off, OSC
bit set to a 1.
READING THE CLOCK
When reading the RTC data, it is recommended to halt updates to the external set of double-buffered RTC
registers. This puts the external registers into a static state allowing data to be read without register
values changing during the read process. Normal updates to the internal registers continue while in this
state. External updates are halted when a 1 is written into the read bit, B6 of the Control register (1FF8h).
As long as a 1 remains in the Control register read bit, updating is halted. After a halt is issued, the
registers reflect the RTC count (day, date, and time) that was current at the moment the halt command
was issued. Normal updates to the external set of registers will resume within 1 second after the read bit
is set to a 0.
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DS1543
SETTING THE CLOCK
The 8th bit, B7 of the control register is the write bit. Setting the write bit to a 1, like the read bit, halts
updates to the DS1543 (1FF8h-1FFFh) registers. After setting the write bit to a 1, RTC registers can be
loaded with the desired RTC count (day, date, and time) in 24-hour BCD format. Setting the write bit to
a 0 then transfers the values written to the internal RTC registers and allows normal operation to resume.
CLOCK ACCURACY (DIP MODULE)
The DS1543 is guaranteed to keep time accuracy to within ±1 minute per month at 25°C. The RTC is
calibrated at the factory by Dallas Semiconductor using nonvolatile tuning elements. The DS1543 does
not require additional calibration and, in most applications, temperature deviations will have a negligible
effect on accuracy. For this reason, methods of field clock calibration are not available and not necessary.
Attempts to calibrate the RTC that may be used with similar device types (M48T5x family) will not have
any effect even though the DS1543 appears to accept calibration data.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1543 and DS9034PCX are each individually tested for accuracy. Once mounted together, the
module is guaranteed to keep time accuracy to within ±1.53 minutes per month (35 ppm) at 25°C.
FREQUENCY TEST MODE
The DS1543 frequency test mode uses the open-drain IRQ /FT output. With the oscillator running, the
IRQ /FT output will toggle at 512 Hz when the FT bit is a 1, the Alarm Flag Enable bit (AE) is a 0, and
the Watchdog Steering bit (WDS) is a 1 or the Watchdog Register is reset (register 1FF7h = 00h). The
IRQ /FT output and the frequency test mode can be used as a measure of the actual frequency of the
32.768 kHz RTC oscillator. The IRQ /FT pin is an open-drain output which requires a pullup resistor for
proper operation. The FT bit is cleared to a 0 on power-up.
USING THE CLOCK ALARM
The alarm settings and control for the DS1543 reside within registers 1FF2h - 1FF5h. Register 1FF6h
contains two alarm enable bits: Alarm Enable (AE) and Alarm in Backup Enable (ABE). The AE and
ABE bits must be set as described below for the IRQ /FT output to be activated for a matched alarm
condition.
The alarm can be programmed to activate on a specific day of the month or repeat every day, hour,
minute, or second. It can also be programmed to go off while the DS1543 is in the battery-backed state of
operation to serve as a system wake-up. Alarm mask bits AM1-AM4 control the alarm mode. Table 3
shows the possible settings. Configurations not listed in the table default to the once per second mode to
notify the user of an incorrect alarm setting.
ALARM MASK BITS Table 3
AM4
1
1
1
1
0
AM3
1
1
1
0
0
AM2
1
1
0
0
0
AM1
1
0
0
0
0
ALARM RATE
Once per second
When seconds match
When minutes and seconds match
When hours, minutes, and seconds match
When date, hours, minutes, and seconds match
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DS1543
When the RTC register values match alarm register settings, the Alarm Flag bit (AF) is set to a 1. If
Alarm Flag Enable (AE) is also set to a 1, the alarm condition activates the IRQ /FT pin. The IRQ /FT
signal is cleared by a read or write to the Flags register (Address 1FF0h) as shown in Figure 2. The
IRQ /FT signal may be cleared by having the address stable for as short as 15 ns and either CE or WE
active, but is not guaranteed to be cleared unless tRC is fulfilled. The alarm flag is also cleared by a read
or write to the Flags register, but the flag will not change states until the end of the read/write cycle and
the IRQ /FT signal has been cleared.
CLEARING IRQ WAVEFORMS Figure 2
CLEARING IRQ WAVEFORMS Figure 3
The IRQ /FT pin can also be activated in the battery-backed mode. The IRQ /FT will go low if an alarm
occurs and both ABE and AE are set. The ABE and AE bits are cleared during the power-up transition,
however an alarm generated during power-up will set AF. Therefore the AF bit can be read after system
power-up to determine if an alarm was generated during the power-up sequence. Figure 4 illustrates
alarm timing during the battery backup mode and power-up states.
7 of 17
DS1543
BACK-UP MODE ALARM WAVEFORMS Figure 4
USING THE WATCHDOG TIMER
The watchdog timer can be used to detect an out-of-control processor. The user programs the watchdog
timer by setting the desired amount of time-out into the 8-bit Watchdog Register (Address 1FF7h). The
five Watchdog Register bits BMB4-BMB0 store a binary multiplier and the two lower order bits RB1RB0 select the resolution, where 00=1/16 second, 01=1/4 second, 10=1 second, and 11=4 seconds. The
watchdog time-out value is then determined by the multiplication of the 5-bit multiplier value with the 2bit resolution value. (For example: writing 00001110 in the watchdog Register = 3 X 1 second or 3
seconds). If the processor does not reset the timer within the specified period, the Watchdog Flag (WF) is
set and a processor interrupt is generated and stays active until either the Watchdog Flag (WF) is read or
the watchdog register (1FF7) is read or written.
The most significant bit of the Watchdog Register is the Watchdog Steering Bit (WDS). When set to a 0,
the watchdog will activate the IRQ /FT output when the watchdog times out.
When WDS is set to a 1, the watchdog will output a negative pulse on the RST output for a duration of
40 ms to 200 ms. The Watchdog register (1FF7) and the FT bit will reset to a 0 at the end of a watchdog
time-out when the WDS bit is set to a 1.
The watchdog timer resets when the processor performs a read or write of the Watchdog register. The
time-out period then starts over. The watchdog timer is disabled by writing a value of 00h to the
watchdog register. The watchdog function is automatically disabled upon power-up and the Watchdog
register is cleared. If the watchdog function is set to output to the IRQ /FT output and the frequency test
function is activated, the watchdog function prevails and the frequency test function is denied.
POWER-ON DEFAULT STATES
Upon application of power to the device, the following register bits are set to 0:
WDS=0, BMB0-BMB4=0, RB0-RB1=0, AE=0, ABE=0.
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DS1543
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
-5.0V to +6.0V
0°C to 70°C
-55°C to +125°C
260°C for 10 seconds (DIP Package) (See Note 8)
See IPC/JEDEC Standard J-STD-020A for
Surface Mount Devices
* This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
OPERATING RANGE
Range
Commercial
Industrial
Temperature
0°C to +70°C
-40°C to +85°C
VCC
3.3V ± 10% or 5V ± 10%
3.3V ± 10% or 5V ± 10%
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
Logic 1 Voltage All Inputs
VCC = 5V ±10%
VCC = 3.3V ±10%
Logic 0 Voltage All Inputs
VCC = 5V ±10%
VCC = 3.3V ±10%
SYMBOL
MIN
VIH
VIH
VIL
VIL
TYP
(Over the Operating Range)
MAX
UNITS
NOTES
2.2
2.0
VCC +0.3V
VCC +0.3V
V
V
1
1
-0.3
-0.3
0.8
0.6
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Active Supply Current
TTL Standby Current ( CE =VIH )
CMOS Standby Current
( CE ≥=VCC - 0.2V)
Input Leakage Current
(any input)
Output Leakage Current
(any output)
Output Logic 1 Voltage
(IOUT = -1.0 mA)
Output Logic 0 Voltage
(IOUT = 2.1 mA, DQ0-7 Outputs)
(IOUT = 10.0 mA, IRQ /FT and
RST outputs)
Write Protection Voltage
Battery Switch Over Voltage
SYMBOL
ICC
1
1
(VCC = 5.0V ± 10%)
MIN
ICC1
ICC2
TYP
15
MAX
50
UNITS
mA
NOTES
2, 3
1
1
3
3
mA
mA
2, 3
2, 3
IIL
-1
+1
µA
IOL
-1
+1
µA
VOH
2.4
VOL1
VOL2
VPF
VSO
4.25
9 of 17
4.37
VBAT
V
1
0.4
0.4
V
V
1
1, 5
4.50
V
V
1
1, 4
DS1543
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
(VCC = 3.3V ± 10%)
MIN
TYP
MAX
UNITS
NOTES
Active Supply Current
ICC
10
30
mA
2, 3
TTL Standby Current ( CE = VIH )
CMOS Standby Current
( CE ≥=VCC - 0.2V)
Input Leakage Current (any input)
Output Leakage Current
(any output)
Output Logic 1 Voltage
(IOUT = -1.0 mA)
Output Logic 0 Voltage
(IOUT =2.1 mA, DQ0-7 Outputs)
(IOUT =10.0 mA, IRQ /FT and
RST Outputs)
Write Protection Voltage
Battery Switch Over Voltage
ICC1
ICC2
0.7
0.7
2
2
mA
mA
2, 3
2, 3
+1
+1
µA
µA
IIL
IOL
-1
-1
VOH
2.4
VOL1
VOL2
VPF
VSO
2.80
READ CYCLE TIMING DIAGRAM Figure 5
10 of 17
2.88
VBAT
or VPF
V
1
0.4
0.4
V
V
1
1, 5
2.97
V
V
1
1, 4
DS1543
READ CYCLE, AC CHARACTERISTICS
PARAMETER
Read Cycle Time
Address Access Time
to DQ Low-Z
CE Access Time
CE Data Off time
OE to DQ Low-Z
OE Access Time
OE Data Off Time
Output Hold from Address
CE
SYMBOL
tRC
tAA
tCEL
tCEA
tCEZ
tOEL
tOEA
tOEZ
tOH
70 ns access
MIN MAX
70
70
5
70
25
5
35
25
5
READ CYCLE, AC CHARACTERISTICS
PARAMETER
Read Cycle Time
Address Access Time
to DQ Low-Z
CE Access Time
CE Data Off time
OE to DQ Low-Z
OE Access Time
OE Data Off Time
Output Hold from Address
CE
SYMBOL
tRC
tAA
tCEL
tCEA
tCEZ
tOEL
tOEA
tOEZ
tOH
120 ns access
MIN MAX
120
120
5
120
40
5
100
35
5
11 of 17
(VCC = 5.0V ±10%)
100 ns access
MIN MAX
100
100
5
100
35
5
55
35
5
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
NOTES
(VCC = 3.3V ±10%)
150 ns access
MIN MAX
150
150
5
150
50
5
130
35
5
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
NOTES
5
5
5
5
5
5
5
5
5
DS1543
WRITE CYCLE, AC CHARACTERISTICS
PARAMETER
Write Cycle Time
Address Access Time
Pulse Width
CE Pulse Time
Data Setup Time
Data Hold time
Address Hold Time
WE
Data Off Time
Write Recovery Time
WE
SYMBOL
tWC
tAS
tWEW
tCEW
tDS
tDH
tAH
tWEZ
tWR
70 ns access
MIN MAX
70
0
50
60
30
0
5
25
5
WRITE CYCLE, AC CHARACTERISTICS
PARAMETER
Write Cycle Time
Address Setup Time
Pulse Width
CE Pulse Width
Data Setup Time
Data Hold Time
Address Hold Time
WE
Data Off Time
Write Recovery Time
WE
SYMBOL
tWC
tAS
tWEW
tCEW
tDS
tDH
tAH
tWEZ
tWR
120 ns access
MIN MAX
120
0
100
110
80
0
0
40
10
12 of 17
(VCC = 5.0V ±10%)
100 ns access
MIN MAX
100
0
70
75
40
0
5
35
5
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
NOTES
(VCC = 3.3V ±10%)
150 ns access
MIN MAX
150
0
130
140
90
0
0
50
10
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
NOTES
5
5
5
5
5
5
5
5
5
DS1543
WRITE CYCLE TIMING, WRITE ENABLE CONTROLLED Figure 6
WRITE CYCLE TIMING, CHIP ENABLE CONTROLLED Figure 7
13 of 17
DS1543
(VCC = 5.0V ±10%)
POWER-UP/DOWN CHARACTERISTICS
PARAMETER
CE or WE at VIH , Before
Power-Down
VCC Fall Time: VPF(MAX) to
VPF(Min)
VCC Fall Time: VPF(MIN) to VSO
VCC Rise Time: VPF(MIN) to
VPF(MAX)
VPF to RST High
Expected Data Retention Time
(Oscillator On)
SYMBOL
MIN
TYP
MAX
tPD
0
µs
tF
300
µs
tFB
10
µs
tR
0
µs
tREC
40
tDR
10
200
UNITS
ms
years
POWER-UP/DOWN WAVEFORM TIMING 5-VOLT DEVICE Figure 8
14 of 17
NOTES
6, 7
DS1543
(VCC = 3.3V ±10%)
POWER-UP/DOWN CHARACTERISTICS
PARAMETER
CE or WE at VIH , Before
Power-Down
VCC Fall Time: VPF(MAX) to
VPF(Min)
VCC Rise Time: VPF(MIN) to
VPF(MAX)
VPF to RST High
Expected Data Retention Time
(Oscillator On)
SYMBOL
MIN
TYP
MAX
tPD
0
µs
tF
300
µs
tR
0
µs
tREC
40
tDR
0
200
UNITS
NOTES
ms
years
6, 7
POWER-UP/DOWN WAVEFORM TIMING 3.3-VOLT DEVICE Figure 9
CAPACITANCE
PARAMETER
(TA = 25°C)
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Capacitance on all input pins
CIN
7
pF
1
Capacitance on IRQ /FT, RST ,
and DQ pins
CIO
10
pF
1
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DS1543
AC TEST CONDITIONS
Output Load:
100 pF + 1TTL Gate
Input Pulse Levels:
0.0 to 3.0V
Timing Measurement Reference Levels:
Input: 1.5V
Output: 1.5V
Input Pulse Rise and Fall Times: 5 ns
NOTES:
1. Voltage referenced to ground.
2. Typical values are at 25°C and nominal supplies.
3. Outputs are open.
4. Battery switch over occurs at the lower of either the battery voltage or VPF.
5. The IRQ /FT and RST outputs are open-drain.
6. Data retention time is at 25°C.
7. Each DS1543 has a built-in switch that disconnects the lithium source until VCC is first applied by the
user. The expected tDR is defined for DIP modules as a cumulative time in the absence of VCC starting
from the time power is first applied by the user.
8. Real Time Clock Modules (DIP) can be successfully processed through conventional wave-soldering
techniques as long as temperature exposure to the lithium energy source contained within does not
exceed +85°C. Post-solder cleaning with water washing techniques is acceptable, provided that
ultrasonic vibration is not used.
In addition, for the PowerCap:
a. Dallas Semiconductor recommends that PowerCap Module bases experience one pass through solder
reflow oriented with the label side up (“live - bug”).
b. Hand Soldering and touch-up: Do not touch or apply the soldering iron to leads for more than
3 seconds. To solder, apply flux to the pad, heat the lead frame pad and apply solder. To remove the
part, apply flux, heat the lead frame pad until the solder reflow and use a solder wick to remove
solder.
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DS1543
DS1543 28-PIN PACKAGE
17 of 17