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DS1244/DS1244P 256k NV SRAM with Phantom Clock
PIN ASSIGNMENT (Top View)
A14/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 A13 A8 A9 A11 OE A10 CE DQ7 DQ6 DQ5 DQ4 DQ3
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FEATURES
Real-time clock (RTC) keeps track of hundredths of seconds, minutes, hours, days, date of the month, months, and years 32k 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 Month and year determine the number of days in each month; valid up to 2100 Full 10% operating range Operating temperature range: 0C to +70C Over 10 years of data retention in the absence of power Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time DIP module only Standard 28-pin JEDEC pinout PowerCap(R) module board only - Surface mountable package for direct connection to PowerCap containing battery and crystal - Replaceable battery (PowerCap) - Pin-for-pin compatible with DS1248P and DS1251P Underwriters Laboratory (UL) recognized
DS2144 28-PDIP Module (740mil)
RST N.C. N.C. N.C. VCC WE OE CE DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0 GND
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
X1
GND VBAT
X2
34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18
N.C. N.C. A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
DS1244P 34-Pin PowerCap Module (Uses DS9034PCX PowerCap)
Package Dimension Information
http://www.maxim-ic.com/TechSupport/DallasPackInfo.htm
PowerCap is a registered trademark of Dallas Semiconductor.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: http://www.maxim-ic.com/errata.
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081902
DS1244/DS1244P
PIN DESCRIPTION
A0-A14
CE OE WE
TYPICAL OPERATING CIRCUIT
VCC GND DQ0-DQ7 N.C. X1, X2 VBAT
RST
- Address Inputs - Chip Enable - Output Enable - Write Enable - Power-Supply Input - Ground - Data In/Data Out - No Connection - Crystal Connection - Battery Connection - Reset
ORDERING INFORMATION
PART DS1244Y-70 DS1244YP-70 DS1244W-120 DS1244W-120IND DS1244WP-120 DS1244WP-120IND PIN-PACKAGE 28-Module (740mil) 34-PowerCap* 28-Module (740mil) 28-Module (740mil) 34-PowerCap* 34-PowerCap* TEMP RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C 0C to +70C -40C to +85C TOP MARK DS1244Y-70 DS1244YP-70 DS1244W-120 DS1244W-120IND DS1244WP-120 DS1244WP-120IND
* DS9034PCX (PowerCap) Required. (Must be ordered separately.)
DESCRIPTION
The DS1244 256k NV SRAM with a Phantom clock is a fully static nonvolatile RAM (NV SRAM) (organized as 32k words by 8 bits) with a built-in real-time clock. The DS1244 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 for hundredths of seconds, seconds, minutes, hours, days, date, 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 DS1244 is available in two packages: 28-pin DIP and 34-pin PowerCap module. The 28-pin DIPstyle 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 PowerCap to be mounted on top of the DS1244P 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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DS1244/DS1244P
RAM READ MODE
The DS1244 executes a read cycle whenever WE (write enable) is inactive (high) and CE (chip enable) is active (low). The unique address specified by the 15 address inputs (A0-A14) defines which of the 32,768 bytes of data is to be accessed. Valid data is available to the eight data-output drivers within tACC (access time) after the last address input signal is stable, providing that CE and OE (output enable) access times and states are also satisfied. If OE and CE access times are not satisfied, then data access must be measured from the later occurring signal ( CE or OE ) and the limiting parameter is either tCO for CE or tOE for OE , rather than address access.
RAM WRITE MODE
The DS1244 is in the write mode whenever the WE and CE signals are in the active (low) state after address inputs are stable. The latter occurring falling edge of CE or WE will determine the start of the write cycle. The write cycle is terminated by the earlier rising edge of CE or WE . All address inputs must be kept valid throughout the write cycle. WE must return to the high state for a minimum recovery time (tWR ) before another cycle can be initiated. The OE control signal should be kept inactive (high) during write cycles to avoid bus contention. However, if the output bus has been enabled ( CE and OE active) then WE will disable the outputs in tODW from its falling edge.
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 fall as below the 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 the chip enable, output enable, and write enable. Initially, a read cycle to any memory location using
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DS1244/DS1244P
the CE and OE control of the phantom clock starts the pattern recognition sequence by moving a pointer to the first bit of the 64-bit comparison register. Next, 64 consecutive write cycles are executed using the CE and WE control of the SmartWatch. These 64 write cycles are used only to gain access to the 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 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 OE pin or the WE pin. Cycles to other locations outside the memory block can be interleaved with CE cycles without interrupting the pattern 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 (BCD) format. 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.
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DS1244/DS1244P
Figure 1. PHANTOM CLOCK REGISTER DEFINITION
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.
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DS1244/DS1244P
Figure 2. PHANTOM CLOCK REGISTER DEFINITION
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 second 10-hour bit (20-23 hours).
OSCILLATOR AND RESET BITS
Bits 4 and 5 of the day register are used to control the RESET and oscillator functions. Bit 4 controls the RESET (pin 1). When the RESET bit is set to logic 1, the RESET input pin is ignored. When the RESET bit is set to logic 0, a low input on the RESET pin will cause the phantom clock to abort data transfer without changing 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 that always read logic 0. When writing these locations, either a logic 1 or 0 is acceptable.
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DS1244/DS1244P
BATTERY LONGEVITY
The DS1244 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 DS1244 continuously for the life of the equipment in which it is installed. For specification purposes, the life expectancy is 10 years at +25C with the internal clock oscillator running in the absence of VCC power. Each DS1244 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 DS1244 will be much longer than 10 years since no lithium battery energy is consumed when VCC is present. See "Conditions of Acceptability" at http://www.maxim-ic.com/TechSupport/QA/ntrl.htm.
CLOCK ACCURACY (DIP MODULE)
The DS1244 is guaranteed to keep time accuracy to within 1 minute per month at +25C. The clock is calibrated at the factory by Dallas Semiconductor using special calibration nonvolatile tuning elements and does not require additional calibration. For this reason, methods of field clock calibration are not available and not necessary.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1244P and DS9034PCX are each individually tested for accuracy. Once mounted together, the module will typically keep time accuracy to within 1.53 minutes per month (35ppm) at +25C.
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DS1244/DS1244P
ABSOLUTE MAXIMUM RATINGS*
Voltage Range on Any Pin Relative to Ground Storage Temperature Range Soldering Temperature Range -0.3V to +6.0V -40C to +85C See IPC/JEDEC J-STD-020A (DIP) (Note 13)
OPERATING RANGE
RANGE Commercial Industrial TEMP RANGE 0C to +70C -40C to +85C VCC 3.3V 10% or 5V 10% 3.3V 10% or 5V 10%
*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.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER SYMBOL MIN TYP
Over the operating range MAX UNITS NOTES
Input Logic 1
VCC = 5V 10% VCC = 3.3V 10% VCC = 5V 15% VCC = 3.3V 10%
VIH
2.2 2.0 -0.3 -0.3
VCC + 0.3V VCC + 3V 0.8 0.6
V
11
Input Logic 0
VIL
V
11
DC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL MIN TYP
Over the operating range (5V) MAX UNITS mA mA NOTES
Input Leakage Current I/O Leakage Current CE VIH VCC Output Current at 2.4V Output Current at 0.4V Standby Current CE = 2.2V Standby Current CE = VCC - 0.5V Operating Current tCYC = 70ns Write Protection Voltage Battery Switchover Voltage
IIL IIO IOH IOL ICCS1 ICCS2 ICC01 VPF VSO
-1.0 -1.0 -1.0 2.0 5 3.0
+1.0 +1.0
12
mA mA 10 5.0 85 4.50 mA mA mA V V
4.25
4.37 VBAT
11 11
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DS1244/DS1244P
DC ELECTRICAL CHARACTERISTICS
PARAMETER Input Leakage Current I/O Leakage Current CE VIH VCC Output Current at 2.4V Output Current at 0.4V Standby Current CE = 2.2V Standby Current CE = VCC - 0.5V Operating Current tCYC = 70ns Write Protection Voltage Battery Switchover Voltage SYMBOL IIL MIN -1.0 TYP
Over the operating range (3.3V) MAX +1.0 UNITS mA mA NOTES 12
IIO IOH IOL ICCS1 ICCS2 ICC01 VPF VSO
-1.0 -1.0 2.0 5 2.0 2.80 2.86 VBAT or VPF
+1.0
7 3.0 50 2.97
mA mA mA mA mA V V 11 11
(TA = +25C)
CAPACITANCE
PARAMETER Input Capacitance Input/Output Capacitance SYMBOL CIN CI/O MIN TYP 5 5 MAX 10 10
UNITS pF pF
NOTES
MEMORY AC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL
Over the operating range (5V) UNITS NOTES
Read Cycle Time Access Time OE to Output Valid CE to Output Valid OE or CE to Output Active Output High-Z from Deselection Output Hold from Address Change Write Cycle Time Write Pulse Width Address Setup Time Write Recovery Time Output High-Z from WE Output Active from WE Data Setup Time Data Hold Time from WE
tRC tACC tOE tCO tCOE tOD tOH tWC tWP tAW tWR tODW tOEW tDS tDH
DS1244Y-70 MIN MAX 70 70 35 70 5 25 5 70 50 0 0 25 5 30 5
ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
5 5 3 5 5 4 4
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DS1244/DS1244P
PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS
PARAMETER Read Cycle Time 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 Write Cycle Time Write Pulse Width Write Recovery Data Setup Time Data Hold Time CE Pulse Width RESET Pulse Width SYMBOL tRC tCO tOE tCOE tOEE tOD tODO tRR tWC tWP tWR tDS tDH tCW tRST MIN 65 TYP Over the operating range (5V) MAX UNITS NOTES ns 55 ns 55 ns ns ns 25 ns 5 25 ns 5 ns ns ns 3 ns 10 ns 4 ns 4 ns ns Over the operating range (5V) MIN 0 300 TYP MAX UNITS ms ms ms ms NOTES
5 5
10 65 55 10 30 0 60 65
POWER-DOWN/POWER-UP TIMING
PARAMETER CE at VIH before Power-Down VCC Slew from VPF(max) to 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 SYMBOL tPD tF
tFB tR tREC
10 0 1.5 2.5
ms
(TA = +25C)
PARAMETER Expected Data Retention Time
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
tDR
10
years
9
Warning: Under no circumstances are negative undershoots of any amplitude allowed when device is in battery-backup mode.
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DS1244/DS1244P
MEMORY AC ELECTRICAL CHARACTERISTICS
PARAMETER SYMBOL Over the operating range (3.3V) DS1244W-120 UNITS NOTES MIN MAX 120 ns 120 ns 60 ns 120 ns 5 ns 5 40 ns 5 5 ns 120 ns 90 ns 3 0 ns 20 ns 10 40 ns 5 5 ns 5 50 ns 4 20 ns 4
Read Cycle Time Access Time OE to Output Valid CE to Output Valid OE or CE to Output Active Output High-Z from Deselection Output Hold from Address Change Write Cycle Time Write Pulse Width Address Setup Time Write Recovery Time Output High-Z from WE Output Active from WE Data Setup Time Data Hold Time from WE
tRC tACC tOE tCO tCOE tOD tOH tWC tWP tAW tWR tODW tOEW tDS tDH
PHANTOM CLOCK AC ELECTRICAL CHARACTERISTICS
PARAMETER Read Cycle Time 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 Write Cycle Time Write Pulse Width Write Recovery Data Setup Time Data Hold Time CE Pulse Width RESET Pulse Width SYMBOL tRC tCO tOE tCOE tOEE tOD tODO tRR tWC tWP tWR tDS tDH tCW tRST MIN 120 Over the operating range (3.3V) TYP MAX UNITS NOTES ns 100 ns 100 ns ns ns 40 ns 5 40 ns 5 ns ns ns 3 ns 10 ns 4 ns 4 ns ns
5 5
20 120 100 20 45 0 105 120
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DS1244/DS1244P
POWER-DOWN/POWER-UP TIMING
PARAMETER CE at VIH before Power-Down VCC Slew from VPF(MAX) to VPF(MIN)( CE at VIH) VCC Slew from VPF(MAX) to VPF(MIN)( CE at VIH) CE at VIH after Power-Up SYMBOL tPD tF MIN 0 300 TYP
Over the operating range (3.3V) MAX UNITS ms ms ms NOTES
tR tREC
0 1.5 2.5
ms
(TA = +25C)
PARAMETER Expected Data Retention Time
SYMBOL tDR
MIN 10
TYP
MAX
UNITS years
NOTES 9
Warning: Under no circumstances are negative undershoots, of any amplitude, allowed when device is in battery-backup mode.
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DS1244/DS1244P
MEMORY READ CYCLE (Note 1)
MEMORY WRITE CYCLE 1 (Notes 2, 6, and 7)
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DS1244/DS1244P
MEMORY WRITE CYCLE 2 (Notes 2 and 8)
RESET FOR PHANTOM CLOCK
READ CYCLE TO PHANTOM CLOCK
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DS1244/DS1244P
WRITE CYCLE TO PHANTOM CLOCK
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DS1244/DS1244P
POWER-DOWN/POWER-UP CONDITION, 5V
POWER-DOWN/POWER-UP CONDITION, 3.3V
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DS1244/DS1244P
AC TEST CONDITIONS
Output Load: Input Pulse Levels: 50pF + 1TTL Gate 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, tDS 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 referencd to ground. 12) RST (Pin 1) has an internal pullup resistor. 13) RTC 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 +85C. Postsolder cleaning with water-washing techniques is acceptable, provided that ultrasonic vibration is not used. In addition, for the PowerCap: 1) Dallas Semiconductor 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.
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DS1244/DS1244P
DS1244P WITH DS9034PCX ATTACHED
PKG DIM A B C D E F G MIN 0.920 0.955 0.240 0.052 0.048 0.015 0.020 INCHES NOM 0.925 0.960 0.245 0.055 0.050 0.020 0.025 MAX 0.930 0.965 0.250 0.058 0.052 0.025 0.030
COMPONENTS AND PLACEMENT MIGHT VARY FROM EACH DEVICE TYPE
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DS1244/DS1244P
RECOMMENDED POWERCAP MODULE LAND PATTERN
PKG DIM A B C D E MIN -- -- -- -- -- INCHES NOM MAX 1.050 -- 0.826 -- 0.050 -- 0.030 -- 0.112 --
Note: Dallas Semiconductor recommends that PowerCap module bases experience one pass through solder reflow oriented with the label side up ("live-bug").
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.
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