1 of 13 REV: 041105
FEATURES
§ Integrates NV SRAM, Real-Time Clock,
Crystal, Power-Fail Control Circuit and
Lithium Energy Source
§ Clock Registers are Accessed Identically to
the Static RAM. These Registers are
Resident in the Eight Top RAM Locations
§ Totally Nonvolatile with Over 10 Years of
Operation in the Absence of Power
§ BCD-Coded Year, Month, Date, Day, Hours,
Minutes, and Seconds with Leap Year
Compensation Valid Up to 2100
§ Power-Fail Write Protection Allows for
±10% VCC Power Supply Tolerance
§ DS1646 only (DIP Module)
Standard JEDEC Bytewide 128k x 8 RAM
Pinout
§ DS1646P Only (PowerCap® Module Board)
Surface Mountable Package for Direct
Connection to PowerCap Containing
Battery and Crystal
Replaceable Battery (PowerCap)
Power-Fail Output
Pin-for-Pin Compatible with Other Densities
of DS164xP Timekeeping RAM
Underwriters Laboratory (UL) Recognized
PowerCap is a registered trademark of Dallas Semiconductor.
PIN CONFIGURATIONS
ORDERING INFORMATION
PART VOLTAGE
RANGE (V)
TEMP
RANGE PIN-PACKAGE TOP MARK
DS16460-120 5.0 0°C to +70°C 32 EDIP (0.740a) DS1646+120
DS16460-120 5.0 0°C to +70°C 32 EDIP (0.740a) DS1646-120
DS1646P-120 5.0 0°C to +70°C 34 PowerCap* DS1646P+120
DS1646P-120 5.0 0°C to +70°C 34 PowerCap* DS1646P-120
*DS9034-PCX, DS9034I-PCX, DS9034-PCX+ required (must be ordered separately).
A “+" indicates a lead-free product. The top mark will include a “+" symbol on lead-free devices.
1
N.C. 2
3
A15
A16
PF
O
VCC
W
E
O
E
C
E
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
4
5
6
7
8
9
10
11
12
13
14
15
16
17
N.C.
A
14
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
A
13
A
12
A
11
A
10
A
9
A
8
A
7
A
6
A
5
A
4
A
3
A
2
A
1
A
0
34 N.C.
X1 GND VBAT X2
34-Pin PowerCap Module Board
(Uses DS9034PCX PowerCap)
13
1
2
3
4
5
6
7
8
9
10
11
12
14
31
32-Pin Encapsulated Package
A14
A7
A5
A4
A3
A2
A1
A0
DQ1
DQ0
VCC
A
15
N.C.
WE
A
13
A
8
A
9
A
11
OE
A
10
CE
DQ7
DQ5
DQ6
32
30
29
28
27
26
25
24
23
22
21
19
20
A16
A12
A6
N.C.
DQ2
GND
15
16
18
17
DQ4
DQ3
DS1646/DS1646P
Nonvolatile Timekeeping RAM
www.maxim-ic.com
DS1646/DS1646P
2 of 13
PIN DESCRIPTION
PIN
PDIP PowerCap NAME FUNCTION
1, 30 1, 33, 34 N.C. No Connection
2 3 A16
3 32 A14
4 30 A12
5 25 A7
6 24 A6
7 23 A5
8 22 A4
9 21 A3
10 20 A2
11 19 A1
12 18 A0
25 29 A11
26 27 A9
27 26 A8
28 31 A13
Address Input
13 16 DQ0
14 15 DQ1
15 14 DQ2
17 13 DQ3
18 12 DQ4
19 11 DQ5
20 10 DQ6
21 9 DQ7
Data Input/Output
16 17 GND Ground
22 8 CE Active-Low Chip Enable
23 28 A10 Address Input
24 7 OE Active-Low Output Enable
29 6 WE Active-Low Write Enable
31 2 A15 Address Input
32 5 VCC Power-Supply Input
— 4 PFO Active-Low Power-Fail Output, Open Drain. Requires a pullup
resistor for proper operation.
X1, X2,
VBAT Crystal Connection, VBAT Battery Connection
DS1646/DS1646P
3 of 13
DESCRIPTION
The DS1646 is a 128k x 8 nonvolatile static RAM with a full-function real time clock, which are both
accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any
JEDEC standard 128k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and
EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real
time clock information resides in the eight uppermost RAM locations. The RTC registers contain year,
month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the
month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access
of incorrect data that can occur during clock update cycles. The double-buffered system also prevents
time loss as the timekeeping countdown continues unabated by access to time register data. The DS1646
also contains its own power-fail circuitry, which deselects the device when the VCC supply is in an out-of-
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by
low VCC as errant access and update cycles are avoided.
PACKAGES
The DS1646 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 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
DS1646P 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.
CLOCK OPERATIONS—READING THE CLOCK
While the double-buffered register structure reduces the chance of reading incorrect data, internal updates
to the DS1646 clock registers should be halted before clock data is read to prevent reading of data in
transition. However, halting the internal clock register updating process does not affect clock accuracy.
Updating is halted when a 1 is written into the read bit, the 7th most significant bit in the control register.
As long as 1 remains in that position, updating is halted. After a halt is issued, the registers reflect the
count, that is day, date, and time that was present at the moment the halt command was issued. However,
the internal clock registers of the double-buffered system continue to update so that clock accuracy is not
affected by the access of data. All of the DS1646 registers are updated simultaneously after the clock
status is reset. Updating is within a second after the read bit is written to 0.
DS1646/DS1646P
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BLOCK DIAGRAM DS1646 Figure 1
TRUTH TABLE DS1646 Table 1
VCC CE OE WE MODE DQ POWER
VIH X X DESELECT HIGH-Z STANDBY
X X X DESELECT HIGH-Z STANDBY
VIL X VIL WRITE DATA IN ACTIVE
VIL V
IL V
IH READ DATA OUT ACTIVE
5V ± 10%
VIL V
IH V
IH READ HIGH-Z ACTIVE
<4.5V >VBAT X X X DESELECT HIGH-Z CMOS STANDBY
<VBAT X X X DESELECT HIGH-Z
DATA RETENTION
MODE
SETTING THE CLOCK
The MSB 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 DS1646 registers. The user can then load them with the correct day, date and time data in
24-hour BCD format. Resetting the write bit to a 0 then transfers those values to the actual clock counters
and allows normal operation to resume.
STOPPING AND STARTING THE CLOCK OSCILLATOR
The clock oscillator may be stopped at any time. To increase the shelf life, the oscillator can be turned off
to minimize current drain from the battery. The OSC bit is the MSB for the second’s registers. Setting it
to a 1 stops the oscillator.
FREQUENCY TEST BIT
Bit 6 of the day byte is the frequency test bit. When the frequency test bit is set to logic 1 and
the oscillator is running, the LSB of the second’s register will toggle at 512 Hz. When the seconds
register is being read, the DQ0 line will toggle at the 512 Hz frequency as long as conditions for access
remain valid (i.e., CE low, OE low, and address for seconds register remain valid and stable).
DS1646/DS1646P
5 of 13
CLOCK ACCURACY (DIP MODULE)
The DS1646 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, and does not require
additional calibration. For this reason, methods of field clock calibration are not available and not
necessary. Clock accuracy is also affected by the electrical environment and caution should be taken to
place the RTC in the lowest level EMI section of the PCB layout. For additional information refer to
Application Note 58.
CLOCK ACCURACY (POWERCAP MODULE)
The DS1646 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 (35 ppm) at 25°C. Clock
accuracy is also affected by the electrical environment and caution should be taken to place the RTC in
the lowest level EMI section of the PCB layout. For additional information refer to Application Note 58.
1646 REGISTER MAP—BANK1 Table 2
DATA
ADDRESS B7 B
6 B
5 B
4 B
3 B
2 B
1 B
0 FUNCTION
1FFFF — — — — — — Year 00–99
1FFFE X X X — — — — — Month 01–12
1FFFD X X - — — — — — Date 01–31
1FFFC X FT X X X Day 01–07
1FFFB X X — — — — — — Hour 00–23
1FFFA X — — — — — — Minutes 00–59
1FFF9 OSC — — — — — — Seconds 00–59
1FFF8 W R X X X X X X Control A
OSC = Stop Bit R = Read Bit FT = Frequency Test
W = Write Bit X = Unused
Note: All indicated “X” bits are unused but must be set to “0” during write cycles to ensure proper clock
operation.
RETRIEVING DATA FROM RAM OR CLOCK
The DS1646 is in the read mode whenever WE (write enable) is high; CE (chip enable) is low. The
device architecture allows ripple-through access to any of the address locations in the NVSRAM. Valid
data will be available at the DQ pins within tAA after the last address input is stable, providing that the CE
and OE access times and states 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.
DS1646/DS1646P
6 of 13
WRITING DATA TO RAM OR CLOCK
The DS1646 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 high to low transition of WE and CE . The addresses must be held valid
throughout the cycle. CE or WE must return inactive for a minimum of tWR prior to the initiation of
another read or write cycle. Data in must be valid tDS prior to the end of 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
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
When VCC is within nominal limits (VCC > 4.5 volts) the DS1646 can be accessed as described above with
read or write cycles. However, when VCC is below the power-fail point VPF (point at which write
protection occurs) the internal clock registers and RAM are blocked from access. This is accomplished
internally by inhibiting access via the CE signal. At this time the power-fail output signal ( PFO ) will be
driven active low and will remain active until VCC returns to nominal levels. When VCC falls below the
level of the internal battery supply, power input is switched from the VCC pin to the internal battery and
clock activity, RAM, and clock data are maintained from the battery until VCC is returned to nominal
level.
DS1646/DS1646P
7 of 13
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground……………………………………………..-0.3V to +7.0V
Storage Temperature Range………………………………………………-40°C to +85°C, Noncondensing
Soldering Temperature…………………………………260°C for 10 seconds (DIP Package) (See Note 7)
See IPC/JEDEC Standard J-STD-020 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 TEMPERATURE VCC
Commercial 0°C to +70°C, Noncondensing 5V ±10%
RECOMMENDED DC OPERATING CONDITIONS (Over the Operating Range)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Supply Voltage VCC 4.5 5.0 5.5 V 1
Logic 1 Voltage All Inputs VIH 2.2 VCC+0.3 V
Logic 0 Voltage All Inputs VIL -0.3 0.8 V
DC ELECTRICAL CHARACTERISTICS (Over the Operating Range)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Average VCC Power Supply Current ICC1 85 mA 2, 3
TTL Standby Current ( CE =VIH) ICC2 3 6 mA 2, 3
CMOS Standby Current
(CE =VCC-0.2V) ICC3 2 4.0 mA 2, 3
Input Leakage Current (Any Input) IIL -1 +1
mA
Output Leakage Current IOL -1 +1
mA
Output Logic 1 Voltage
(IOUT = -1.0 mA) VOH 2.4 V
Output Logic 0 Voltage
(IOUT = +2.1 mA) VOL 0.4 V
Power-Fail Voltage VPF 4.0 4.25 4.5 V
DS1646/DS1646P
8 of 13
AC ELECTRICAL CHARACTERISTICS (Over the Operating Range)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Read Cycle Time tRC 120 ns
Address Access Time tAA 120 ns
CE Access Time tCEA 120 ns
CE Data Off Time tCEZ 40 ns
Output Enable Access Time tOEA 100 ns
Output Enable Data Off Time tOEZ 40 ns
Output Enable to DQ Low-Z tOEL 5 ns
CE to DQ Low-Z tCEL 5 ns
Output Hold from Address tOH 5 ns
Write Cycle Time tWC 120 ns
Address Setup Time tAS 0 ns
CE Pulse Width tCEW 100 ns
tAH1 5 ns 5
Address Hold from End of Write tAH2 30 ns 6
Write Pulse Width tWEW 75 ns
WE Data Off Time tWEZ 40 ns
WE or CE Inactive Time tWR 10 ns
Data Setup Time tDS 85 ns
tDH1 0 ns 5
Data Hold Time High tDH2 25 ns 6
AC TEST CONDITIONS
Input Levels: 0V to 3V
Transition Times: 5 ns
CAPACITANCE (TA = +25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Capacitance on All Pins (except DQ) CI 7 pF
Capacitance on DQ Pins CDQ 10 pF
AC ELECTRICAL CHARACTERISTICS
(POWER-UP/DOWN TIMING) (Over the Operating Range)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
CE or WE at VIH before Power-Down tPD 0 ms
VPF (Max) to VPF (Min) VCC Fall Time tF 300 ms
VPF (Min) to VSO VCC Fall Time tFB 10 ms
VSO to VPF (Min) VCC Rise Time tRB 1 ms
VPF (Min) to VPF (Max) VCC Rise Time tR 0 ms
Power-Up tREC 15 35 ms
Expected Data Retention Time
(Oscillator On) tDR 10 years 4
DS1646/DS1646P
9 of 13
DS1646 READ CYCLE TIMING
DS1646 WRITE CYCLE TIMING
DS1646/DS1646P
10 of 13
POWER-DOWN/POWER-UP TIMING
OUTPUT LOAD
DS1646/DS1646P
11 of 13
NOTES:
1) All voltages are referenced to ground.
2) Typical values are at 25°C and nominal supplies.
3) Outputs are open.
4) Data retention time is at 25°C and is calculated from the date code on the device package. The date
code XXYY is the year followed by the week of the year in which the device was manufactured. For
example, 9225 would mean the 25th week of 1992.
5) tAH1, tDH1 are measured from WE going high.
6) tAH2, tDH2 are measured from CE going high.
7) Real-Time Clock Modules (DIP) can be successfully processed through conventional wave-soldering
techniques as long as temperatures 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 version:
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 reflows and use a solder wick to
remove solder.
DS1646/DS1646P
12 of 13
PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline
information, go to www.maxim-ic.com/DallasPackInfo.)
DS1646 32-PIN PACKAGE
PKG 28-PIN
DIM MIN MAX
A IN.
MM
1.670
38.42
1.690
38.93
B IN.
MM
0.715
18.16
0.740
18.80
C IN.
MM
0.335
8.51
0.365
9.27
D IN.
MM
0.075
1.91
0.105
2.67
E IN.
MM
0.015
0.38
0.030
0.76
F IN.
MM
0.140
3.56
0.180
4.57
G IN.
MM
0.090
2.29
0.110
2.79
H IN.
MM
0.590
14.99
0.630
16.00
J IN.
MM
0.010
0.25
0.018
0.45
K IN.
MM
0.015
0.38
0.025
0.64
DS1646P
PKG INCHES
DIM MIN NOM MAX
A 0.920 0.925 0.930
B 0.980 0.985 0.990
C - - 0.080
D 0.052 0.055 0.058
E 0.048 0.050 0.052
F 0.015 0.020 0.025
G 0.025 0.027 0.030
NOTE FOR THE PowerCap VERSION:
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 REFLOWS AND USE A SOLDER WICK
TO REMOVE SOLDER.
DS1646/DS1646P
13 of 13
Maxim/Dallas Semiconductor cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim/Dallas Semiconductor product.
No circuit patent licenses are implied. Maxim/Dallas Semiconductor 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
© 2005 Maxim Integrated Products · Printed USA
The Maxim logo is a registered trademark of Maxim Integrated Products, Inc. The Dallas logo is a registered trademark of Dallas Semiconductor Corporation.
DS1646P WITH DS9034PCX ATTACHED
PKG INCHES
DIM MIN NOM MAX
A 0.920 0.925 0.930
B 0.955 0.960 0.965
C 0.240 0.245 0.250
D 0.052 0.055 0.058
E 0.048 0.050 0.052
F 0.015 0.020 0.025
G 0.020 0.025 0.030
RECOMMENDED POWERCAP MODULE LAND PATTERN
PKG INCHES
DIM MIN NOM MAX
A - 1.050 -
B - 0.826 -
C - 0.050 -
D - 0.030 -
E - 0.112 -
ENGLISH ???? ??? ???
WHAT'S NEW
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DS1646
Part Number Table
Notes:
See the DS1646 QuickView Data Sheet for further information on this product family or download the DS1646 full
data sheet (PDF, 320kB).
1.
Other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales.2.
Didn't Find What You Need? Ask our applications engineers. Expert assistance in finding parts, usually within one
business day.
3.
Part number suffixes: T or T&R = tape and reel; + = RoHS/lead-free; # = RoHS/lead-exempt. More: See full data
sheet or Part Naming Conventions.
4.
* Some packages have variations, listed on the drawing. "PkgCode/Variation" tells which variation the product uses.5.
Part Number
Notes
Free
Sample
Buy
Direct
Package:
TYPE PINS SIZE
DRAWING CODE/VAR *
Temp
RoHS/Lead-Free?
Materials Analysis
DS1646-120
120ns
MOD;32 pin;600
Dwg: 56-G0002-001A (PDF)
Use pkgcode/variation: MDF32-1*
0C to +70C
RoHS/Lead-Free: No
Materials Analysis
DS1646-120+
MOD;32 pin;600
Dwg: 56-G0002-001A (PDF)
Use pkgcode/variation: MDF32+1*
0C to +70C
RoHS/Lead-Free: Yes
Materials Analysis
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