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DS1747 Schematic ( PDF Datasheet ) - Dallas

Teilenummer DS1747
Beschreibung Y2K-Compliant / Nonvolatile Timekeeping RAMs
Hersteller Dallas
Logo Dallas Logo 




Gesamt 18 Seiten
DS1747 Datasheet, Funktion
DS1747/DS1747P
Y2K-Compliant, Nonvolatile Timekeeping RAMs
www.maxim-ic.com
FEATURES
§ Integrated NV SRAM, Real-Time Clock
(RTC), 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.
§ Century Byte Register (Y2K Compliant)
§ Totally Nonvolatile with Over 10 Years of
Operation in the Absence of Power
§ BCD-Coded Century, 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
§ DIP Module Only:
Standard JEDEC Byte-Wide 512k x 8 Static
RAM Pinout
§ PowerCapÒ Module Board Only:
Surface-Mountable Package for Direct
Connection to PowerCap Containing
Battery and Crystal
Replaceable Battery (PowerCap)
Power-On Reset Output
Pin-for-Pin Compatible with Other Densities
of DS174xP Timekeeping RAM
§ Also Available in Industrial Temperature
Range: -40°C to +85°C
PIN CONFIGURATIONS
TOP VIEW
A18
A16
A14
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1 32
2 Dallas 31
3
4
Semiconductor
DS1747
30
29
5 28
6 27
7 26
8 25
9 24
10 23
11 22
12 21
13 20
14 19
15 18
16 17
VCC
A15
A17
WE
A13
A8
A9
A11
OE
A10
CE
DQ7
DQ6
DQ5
DQ4
DQ3
Encapsulated DIP
(512k x 8)
N.C.
A15
A16
RST
VCC
WE
OE
DCQE7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
1
2
3
Dallas
Semiconductor
34
33
32
4
DS1747P
31
5 30
6 29
7 28
8 27
9 26
10 25
11 24
12 23
13 22
14 21
15 20
16
17
X1 GND VBAT X2
19
18
PowerCap Module Board
(Uses DS9034PCX PowerCap)
A18
A17
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
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: www.maxim-ic.com/errata.
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REV: 011204






DS1747 Datasheet, Funktion
DS1747/DS1747P Y2K-Compliant, Nonvolatile Timekeeping RAMs
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 failing point, VPF, (point at which write protection occurs) the
internal clock registers and SRAM are blocked from any access. At this time the power fail reset output
signal (RST) is driven active and will remain active until VCC returns to nominal levels. 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. At
this time the power fail reset output signal (RST) is driven active and will remain active until VCC returns
to nominal levels. If VPF is less than VSO, the device power is switched from VCC to the backup supply
(VBAT) when VCC drops below VPF. If VPF is greater than Vso, the device power is switched from VCC to
the backup supply (VBAT) when VCC drops below VSO. RTC operation and SRAM data are maintained
from the battery until VCC is returned to nominal levels. The RST signal is an open drain output and
requires a pull up. Except for the RST, all control, data, and address signals must be powered down
when VCC is powered down.
BATTERY LONGEVITY
The DS1747 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 DS1747 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 DS1747 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 DS1747 will be much longer than 10 years since no lithium battery energy is
consumed when VCC is present.
BATTERY MONITOR
The DS1747 constantly monitors the battery voltage of the internal battery. The Battery Flag bit (bit 7)
of the day register is used to indicate the voltage level range of the battery. This bit is not writable and
should always be a one when read. If a zero is ever present, an exhausted lithium energy source is
indicated and both the contents of the RTC and RAM are questionable.
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DS1747 pdf, datenblatt
DS1747/DS1747P Y2K-Compliant, Nonvolatile Timekeeping RAMs
POWER-UP/DOWN AC CHARACTERISTICS (5V)
(VCC = 5.0V ±10%, TA = Over the Operating Range.)
PARAMETER
SYMBOL MIN TYP
CE or WE at VH
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)
Power-Up Recover Time
Expected Data-Retention Time
(Oscillator ON)
tPD 0
tF 300
tFB 10
tR 0
tREC
tDR 10
MAX
35
UNITS
ms
ms
ms
ms
ms
years
NOTES
5, 6
POWER-UP/DOWN TIMING (5V DEVICE)
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12 Page





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