DS1251WP-120IND [MAXIM]
Real Time Clock, Non-Volatile, CMOS, POWERCAP MODULE-34;
| 型号： | DS1251WP-120IND |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Real Time Clock, Non-Volatile, CMOS, POWERCAP MODULE-34 PC 双倍数据速率 外围集成电路 |
| 文件： | 总20页 (文件大小：539K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-6079; Rev 11/11
DS1251/DS1251P
4096K NV SRAM with Phantom Clock
FEATURES
PIN CONFIGURATIONS
. Real-Time Clock Keeps Track of Hundredths
Of Seconds, Minutes, Hours, Days, Date of
the Month, Months, and Years
. 512K x 8 NV SRAM Directly Replaces
Volatile Static RAM or EEPROM
. Embedded Lithium Energy Cell Maintains
Calendar Operation and Retains RAM Data
. Watch Function is Transparent to RAM
Operation
. Automatic Leap Year Compensation Valid
Up to 2100
. Over 10 Years of Data Retention in the
Absence of Power
TOP VIEW
VCC
A15
A17
WE
A13
A8
A9
A11
OE
1
32
31
A18/RST
A16
A14
A12
A7
A6
A5
2
3
4
DS1251
30
29
5
6
28
27
7
8
26
25
A4
A3
A2
A1
9
10
24
23
A10
CE
11
12
22
21
DQ7
A0
13
14
15
16
20
19
18
17
DQ6
DQ5
DQ4
DQ3
DQ0
DQ1
DQ2
. Full 10% Operating Range
. Lithium Energy Source is Electrically
Disconnected to Retain Freshness Until
Power is Applied for the First Time
. DIP Module Only
– Standard 32-Pin JEDEC Pinout
– Upward Compatible with the DS1248
. PowerCap Module Board Only
GND
Encapsulated Package
740-Mil Flush
A18
A17
A14
34
33
32
31
30
29
28
27
26
25
24
23
22
1
2
3
4
5
6
7
8
9
RST
A15
A16
DS1251P
−
Surface Mountable Package for Direct
Connection to PowerCap Containing
Battery and Crystal
A13
A12
A11
A10
A9
N.C.
VCC
WE
OE
−
−
Replaceable Battery (PowerCap)
Pin-for-Pin Compatible with Other
Densities of DS124xP Phantom Clocks
CE
A8
DQ7
A7
A6
A5
A4
A3
A2
A1
A0
10
11
12
13
14
15
16
17
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
. Underwriters Laboratories (UL) Recognized
21
20
19
(www.maxim-ic.com/qa/info/ul/)
VBAT
X1 GND
X2
18
PowerCap Module Board
(Uses DS9034PCX+ PowerCap)
1 of 20
DS1251/DS1251P
ORDERING INFORMATION
VOLTAGE
RANGE (V)
PART
TEMP RANGE
PIN-PACKAGE
DS1251W-120+
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
3.3
3.3
3.3
3.3
5.0
5.0
5.0
32 EDIP (0.740a)
32 EDIP (0.740a)
34 PowerCap*
34 PowerCap*
32 EDIP (0.740a)
34 PowerCap*
34 PowerCap*
DS1251W-120IND+
DS1251WP-120+
DS1251WP-120IND+
DS1251Y-70+
DS1251YP-70+
DS1251YP-70IND+
+ Denotes a lead(Pb)-free/RoHS-compliant package.
*DS9034PCX+ or DS9034I-PCX+ (PowerCap) required. Must be ordered separately.
PIN DESCRIPTION
PIN
NAME
FUNCTION
Active-Low Reset Input. This pin has an internal pullup resistor connected to VCC.
EDIP PowerCap
1
1
2
3
4
5
6
7
1
34
3
RST
A18
A16
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
A10
A11
A9
32
30
25
24
23
22
21
20
19
18
28
29
27
26
31
33
2
16
15
14
13
12
11
10
9
8
9
10
11
12
23
25
26
27
28
30
31
13
14
15
17
18
19
20
21
Address Inputs
A8
A13
A17
A15
DQ0
DQ1
DQ2
DQ3
DQ4
DQ5
DQ6
DQ7
Data In/Data Out
2 of 20
DS1251/DS1251P
PIN DESCRIPTION (continued)
PIN
NAME
FUNCTION
EDIP PowerCap
22
24
29
32
—
16
8
7
6
5
4
Active-Low Chip-Enable Input
Active-Low Output-Enable Input
Active-Low Write-Enable Input
Power-Supply Input
CE
OE
WE
VCC
N.C.
No Connection
17
GND Ground
DESCRIPTION
The DS1251 4096K NV SRAM with Phantom Clock is a fully static nonvolatile RAM (organized as
512K words by 8 bits) with a built-in real-time clock. The DS1251Y has a self-contained lithium energy
source and control circuitry, which constantly monitors VCC for an out-of-tolerance condition. When such
a condition occurs, the lithium energy source is automatically switched on and write protection is
unconditionally enabled to prevent garbled data in both the memory and real-time clock.
The phantom clock provides timekeeping information including hundredths of seconds, seconds, minutes,
hours, days, dates, months, and years. The date at the end of the month is automatically adjusted for
months with fewer than 31 days, including correction for leap years. The phantom clock operates in either
24-hour or 12-hour format with an AM/PM indicator.
PACKAGES
The DS1251 is available in two packages: 32-pin DIP and 34-pin PowerCap module. The 32-pin DIP
style module integrates the crystal, lithium energy source, and silicon 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 PowerCap to be mounted on top of the
DS1251P after the completion of the surface mount process. Mounting the PowerCap after the surface
mount process prevents damage to the crystal and battery because of 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.
RAM READ MODE
The DS1251 executes a read cycle whenever
(write enable) is inactive (high) and
(chip enable) is
CE
WE
active (low). The unique address specified by the 19 address inputs (A0–A18) defines which of the 512K
bytes of data is to be accessed. Valid data will be available to the eight data-output drivers within tACC
(access time) after the last address input signal is stable, providing that
and
(output enable) access
OE
CE
times and states are also satisfied. If
and
access times are not satisfied, then data access must be
CE
OE
measured from the later occurring signal (
or
) and the limiting parameter is either tCO for
or
CE
CE
OE
tOE for
, rather than address access.
OE
RAM WRITE MODE
The DS1251 is in the write mode whenever the
and
signals are in the active (low) state after
CE
WE
address inputs are stable. The latter occurring falling edge of
or
will determine the start of the
CE
WE
CE
write cycle. The write cycle is terminated by the earlier rising edge of
or
. All address inputs must
WE
3 of 20
DS1251/DS1251P
be kept valid throughout the write cycle.
must return to the high state for a minimum recovery time
WE
(tWR ) before another cycle can be initiated. The
control signal should be kept inactive (high) during
OE
write cycles to avoid bus contention. However, if the output bus has been enabled (
and
active)
OE
CE
then
will disable the outputs in tODW from its falling edge.
WE
DATA RETENTION MODE
The 5V device is fully accessible and data can be written or 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 backup battery. RTC
operation and SRAM data are maintained from the battery until VCC is returned to nominal levels.
The 3.3V device is fully accessible and data can be written or read only when VCC is greater than VPF.
When VCC falls below the power-fail point, VPF , access to the device is inhibited. If VPF is less than VBAT,
the device power is switched from VCC to the backup supply (VBAT ) when VCC drops below VPF . If VPF is
greater than VBAT, the device power is switched from VCC to the backup supply (VBAT ) 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.
PHANTOM CLOCK OPERATION
Communication with the phantom clock is established by pattern recognition on a serial bit stream of
64 bits, which must be matched by executing 64 consecutive write cycles containing the proper data on
DQ0. All accesses that occur prior to recognition of the 64-bit pattern are directed to memory.
After recognition is established, the next 64 read or write cycles either extract or update data in the
phantom clock, and memory access is inhibited.
Data transfer to and from the timekeeping function is accomplished with a serial bit stream under control
of chip enable, output enable, and write enable. Initially, a read cycle to any memory location using the
and
control of the phantom clock starts the pattern recognition sequence by moving a pointer to
OE
CE
the first bit of the 64-bit comparison register. Next, 64 consecutive write cycles are executed using the
and control of the SmartWatch. These 64 write cycles are used only to gain access to the
CE
WE
phantom clock. Therefore, any address to the memory in the socket is acceptable. However, the write
cycles generated to gain access to the phantom clock are also writing data to a location in the mated
RAM. The preferred way to manage this requirement is to set aside just one address location in RAM as a
phantom clock scratch pad. When the first write cycle is executed, it is compared to bit 0 of the 64-bit
comparison register. If a match is found, the pointer increments to the next location of the comparison
register and awaits the next write cycle. If a match is not found, the pointer does not advance and all
subsequent write cycles are ignored. If a read cycle occurs at any time during pattern recognition, the
present sequence is aborted and the comparison register pointer is reset. Pattern recognition continues for
a total of 64 write cycles as described above until all the bits in the comparison register have been
matched (Figure 1). With a correct match for 64 bits, the phantom clock is enabled and data transfer to or
4 of 20
DS1251/DS1251P
from the timekeeping registers can proceed. The next 64 cycles will cause the phantom clock to either
receive or transmit data on DQ0, depending on the level of the
pin or the
pin. Cycles to other
WE
OE
locations outside the memory block can be interleaved with
cycles without interrupting the pattern
CE
recognition sequence or data transfer sequence to the phantom clock.
PHANTOM CLOCK REGISTER INFORMATION
The phantom clock information is contained in eight registers of 8 bits, each of which is sequentially
accessed 1 bit at a time after the 64-bit pattern recognition sequence has been completed. When updating
the phantom clock registers, each register must be handled in groups of 8 bits. Writing and reading
individual bits within a register could produce erroneous results. These read/write registers are defined in
Figure 2.
Data contained in the phantom clock register is in binary-coded decimal format (BCD). Reading and
writing the registers is always accomplished by stepping through all eight registers, starting with bit 0 of
register 0 and ending with bit 7 of register 7.
PHANTOM CLOCK REGISTER DEFINITION Figure 1
NOTE: THE PATTERN RECOGNITION IN HEX IS C5, 3A, A3, 5C, C5, 3A, A3, 5C. THE ODDS OF THIS PATTERN BEING ACCIDENTALLY
DUPLICATED AND CAUSING INADVERTENT ENTRY TO THE PHANTOM CLOCK IS LESS THAN 1 IN 1019. THIS PATTERN IS SENT TO
THE PHANTOM CLOCK LSB TO MSB.
5 of 20
DS1251/DS1251P
PHANTOM CLOCK REGISTER DEFINITION Figure 2
AM/PM/12/24 MODE
Bit 7 of the hours register is defined as the 12-hour or 24-hour mode-select bit. When high, the 12-hour
mode is selected. In the 12-hour mode, bit 5 is the AM/PM bit with logic high being PM. In the 24-hour
mode, bit 5 is the 20-hour bit (20–23 hours).
OSCILLATOR AND RESET BITS
Bits 4 and 5 of the day register are used to control the
and oscillator functions. Bit 4 controls the
RST
(pin 1). When the
bit is set to logic 1, the
input pin is ignored. When the
bit is set to
RST
RST
RST
RST
logic 0, a low input on the
pin will cause the phantom clock to abort data transfer without changing
RST
data in the watch registers. Bit 5 controls the oscillator. When set to logic 1, the oscillator is off. When set
to logic 0, the oscillator turns on and the watch becomes operational. These bits are shipped from the
factory set to a logic 1.
ZERO BITS
Registers 1, 2, 3, 4, 5, and 6 contain one or more bits, which will always read logic 0. When writing these
locations, either a logic 1 or 0 is acceptable.
6 of 20
DS1251/DS1251P
BATTERY LONGEVITY
The DS1251 has a lithium power source that is designed to provide energy for 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 DS1251 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 power. Each DS1251 is shipped from Maxim 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 DS1251 will
be much longer than 10 years since no lithium battery energy is consumed when VCC is present.
CLOCK ACCURACY (DIP MODULE)
The DS1251 is guaranteed to keep time accuracy to within ±1 minute per month at +25°C. The clock is
calibrated at the factory by Maxim using special calibration nonvolatile tuning elements. The DS1251
does not require additional calibration and temperature deviations will have a negligible effect in most
applications. For this reason, methods of field clock calibration are not available and not necessary.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1251P 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 (35ppm) at +25°C.
7 of 20
DS1251/DS1251P
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground
(5V product) . . . . . . . . . . . . . . . . . . . -0.3V to +6.0V
(3.3V product) . . . . . . . . . . . . . . . . . -0.3V to +4.6V
Storage Temperature Range
EDIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C
PowerCap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55°C to +125°C
Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +260°C
Note: EDIP is wave or hand-soldered only
Soldering Temperature (reflow, PowerCap) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+260°C
This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in
the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended
periods of time can affect reliability.
OPERATING RANGE
TEMP RANGE
(NONCONDENSING)
0°C to +70°C
RANGE
VCC (V)
Commercial
Industrial
3.3 ±10% or 5 ±10%
3.3 ±10% or 5 ±10%
-40°C to +85°C
RECOMMENDED OPERATING CONDITIONS
(TA = Over the operating range.)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
V
CC = 5V ±10%
2.2
VCC + 0.3
Logic 1 Voltage All
Inputs
VIH
V
V
11
11
VCC = 3.3V ±10%
2.0
-0.3
-0.3
VCC + 0.3
+0.8
VCC = 5V ±10%
Logic 0 Voltage All
Inputs
VIL
VCC = 3.3V ±10%
+0.6
8 of 20
DS1251/DS1251P
DC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (5V)
PARAMETER
Input Leakage Current
SYMBOL
MIN
TYP
MAX
UNITS NOTES
IIL
IIO
-1.0
+1.0
12
µA
µA
I/O Leakage Current
CE ≥ VIH ≤ VCC
-1.0
+1.0
Output Current at 2.4V
Output Current at 0.4V
IOH
IOL
-1.0
2.0
mA
mA
Standby Current CE = 2.2V
ICCS1
5
10
mA
Standby Current
CE = VCC - 0.5V
ICCS2
3.0
5.0
mA
Operating Current tCYC = 70ns
Write Protection Voltage
ICC01
VPF
85
mA
V
4.25
4.37
4.50
11
11
Battery Switchover Voltage
VSO
VBAT
V
DC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (3.3V)
PARAMETER
Input Leakage Current
SYMBOL
MIN
TYP
MAX
UNITS NOTES
IIL
IIO
-1.0
+1.0
12
µA
µA
I/O Leakage Current
CE ≥ VIH ≤ VCC
-1.0
+1.0
Output Current at 2.4V
Output Current at 0.4V
Standby Current CE = 2.2V
Standby Current
IOH
IOL
-1.0
2.0
mA
mA
mA
ICCS1
5
7
ICCS2
2.0
3.0
mA
CE = VCC - 0.5V
Operating Current tCYC = 70ns
Write Protection Voltage
ICC01
VPF
50
mA
V
2.80
2.97
11
11
VBAT or
VPF
Battery Switchover Voltage
VSO
V
CAPACITANCE
(TA = +25°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Input Capacitance
CIN
5
5
10
10
pF
pF
Input/Output Capacitance
CI/O
9 of 20
DS1251/DS1251P
MEMORY AC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (5V)
DS1251Y-70
PARAMETER
Read Cycle Time
SYMBOL
UNITS
NOTES
MIN
MAX
tRC
tACC
tOE
70
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Access Time
70
35
70
OE to Output Valid
CE to Output Valid
tCO
OE or CE to Output Active
Output High-Z from Deselection
Output Hold from Address Change
Write Cycle Time
tCOE
tOD
5
5
5
25
25
tOH
5
70
50
0
tWC
tWP
tAW
tWR
tODW
tOEW
tDS
Write Pulse Width
3
Address Setup Time
Write Recovery Time
Output High-Z from WE
Output Active from WE
Data Setup Time
0
5
5
4
4
5
30
5
Data Hold Time from WE
tDH
10 of 20
DS1251/DS1251P
PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (5V)
PARAMETER
Read Cycle Time
SYMBOL
tRC
MIN
TYP
MAX
UNITS NOTES
65
ns
ns
ns
ns
ns
CE Access Time
OE Access Time
CE to Output Low-Z
OE to Output Low-Z
CE to Output High-Z
OE to Output High-Z
Read Recovery
tCO
55
55
tOE
tCOE
tOEE
tOD
5
5
25
25
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
5
5
tODO
tRR
10
65
55
10
30
0
Write Cycle Time
Write Pulse Width
Write Recovery
tWC
tWP
3
10
4
tWR
Data Setup Time
Data Hold Time
tDS
tDH
4
CE Pulse Width
tCW
60
65
RST Pulse Width
tRST
POWER-DOWN/POWER-UP TIMING
(TA = Over the operating range.) (3.3V)
PARAMETER
SYMBOL
tPD
MIN
TYP
MAX
UNITS NOTES
CE at VIH before Power-Down
0
µs
VCC Slew from VPF(MAX) to
tF
tFB
tR
300
10
0
µs
µs
µs
ms
VPF(MIN)(CE at VPF)
VCC Slew from VPF(MIN) to VSO
VCC Slew from VPF(MAX) to
VPF(MIN) (CE at VPF)
CE at VIH after Power-Up
tREC
1.5
2.5
(TA = +25°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Expected Data Retention Time
tDR
10
years
9
Warning: Under no circumstances are negative undershoots of any amplitude allowed when device
is in battery-backup mode.
11 of 20
DS1251/DS1251P
MEMORY AC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (3.3V)
DS1251W-120
PARAMETER
SYMBOL
UNITS
NOTES
MIN
MAX
Read Cycle Time
tRC
tACC
tOE
120
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Access Time
120
60
OE to Output Valid
CE to Output Valid
tCO
120
OE or CE to Output Active
Output High-Z from Deselection
Output Hold from Address Change
Write Cycle Time
tCOE
tOD
5
5
5
40
40
tOH
5
120
90
0
tWC
tWP
tAW
tWR
tODW
tOEW
tDS
Write Pulse Width
3
Address Setup Time
Write Recovery Time
Output High-Z from WE
Output Active from WE
Data Setup Time
20
10
5
5
5
50
20
4
Data Hold Time from WE
tDH
4
PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS
(TA = Over the operating range.) (3.3V)
PARAMETER
Read Cycle Time
SYMBOL
tRC
MIN
TYP
MAX
UNITS NOTES
120
ns
ns
ns
ns
ns
CE Access Time
OE Access Time
CE to Output Low-Z
OE to Output Low-Z
CE to Output High-Z
OE to Output High-Z
Read Recovery
tCO
100
100
tOE
tCOE
tOEE
tOD
5
5
40
40
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
5
5
tODO
tRR
20
120
100
20
Write Cycle Time
Write Pulse Width
Write Recovery
tWC
tWP
3
10
4
tWR
Data Setup Time
Data Hold Time
tDS
45
tDH
0
4
CE Pulse Width
tCW
105
120
RST Pulse Width
tRST
12 of 20
DS1251/DS1251P
POWER-DOWN/POWER-UP TIMING
(TA = Over the operating range.) (3.3V)
PARAMETER
SYMBOL
tPD
MIN
TYP
MAX
UNITS NOTES
CE at VIH before Power-Down
0
µs
VCC Slew from VPF(MAX) to
VPF(MIN) (CE at VIH)
tF
300
µs
VCC Slew from VPF(MAX) to
VPF(MIN) (CE at VIH)
tR
0
µs
CE at VIH after Power-Up
tREC
1.5
2.5
ms
(TA = +25°C)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS NOTES
Expected Data Retention Time
tDR
10
years
9
Warning: Under no circumstances are negative undershoots of any amplitude allowed when device
is in battery-backup mode.
13 of 20
DS1251/DS1251P
MEMORY READ CYCLE (Note 1)
MEMORY WRITE CYCLE 1 (Notes 2, 6, and 7)
14 of 20
DS1251/DS1251P
MEMORY WRITE CYCLE 2 (Notes 2 and 8)
RESET FOR PHANTOM CLOCK
READ CYCLE TO PHANTOM CLOCK
15 of 20
DS1251/DS1251P
WRITE CYCLE TO PHANTOM CLOCK
POWER-DOWN/POWER-UP CONDITION (5V)
16 of 20
DS1251/DS1251P
POWER-DOWN/POWER-UP CONDITION (3.3V)
17 of 20
DS1251/DS1251P
AC TEST CONDITIONS
Output Load: 50pF + 1TTL Gate
Input Pulse Levels: 0 to 3V
Timing Measurement Reference Levels
Input: 1.5V
Output: 1.5V
Input Pulse Rise and Fall Times: 5ns
NOTES:
1) WE is high for a read cycle.
2) OE = VIH or VIL. If OE = VIH during write cycle, the output buffers remain in a high-impedance state.
3) tWP is specified as the logical AND of CE and WE. tWP is measured from the latter of CE or WE going
low to the earlier of CE or WE going high.
4) tDH, t DS are measured from the earlier of CE or WE going high.
5) These parameters are sampled with a 50pF load and are not 100% tested.
6) If the CE low transition occurs simultaneously with or later than the WE low transition in Write Cycle
1, the output buffers remain in a high-impedance state during this period.
7) If the CE high transition occurs prior to or simultaneously with the WE high transition, the output
buffers remain in a high-impedance state during this period.
8) If WE is low or the WE low transition occurs prior to or simultaneously with the CE low transition,
the output buffers remain in a high impedance state during this period.
9) The expected tDR is defined as cumulative time in the absence of VCC with the clock oscillator
running.
10) tWR is a function of the latter occurring edge of WE or CE.
11) Voltages are referenced to ground.
12) RST (Pin 1) has an internal pullup resistor.
13) Real-time clock modules 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:
1) Maxim recommends that PowerCap Module bases experience one pass through solder reflow oriented
with the label side up (“live-bug”).
2) Hand soldering and touch-up: Do not touch or apply the soldering iron to leads for more than three
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 reflows, and use a solder wick to remove
solder.
18 of 20
DS1251/DS1251P
PACKAGE INFORMATION
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages.
Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a
different suffix character, but the drawing pertains to the package regardless of RoHS status.
PACKAGE TYPE
32 EDIP
PACKAGE CODE
MDT32+5
OUTLINE NO.
21-0245
LAND PATTERN NO.
—
—
34 PWRCP
PC2+5
21-0246
19 of 20
DS1251/DS1251P
REVISION HISTORY
REVISION
PAGES
CHANGED
DESCRIPTION
DATE
Updated the Features, Ordering Information, AM/PM/12/24-MODE, and
Absolute Maximum Ratings, and Package Information sections
11/11
1, 2, 6, 8, 19
20 of 20
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim
reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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