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PDF DS1742 Data sheet ( Hoja de datos )
| Número de pieza | DS1742 | |
| Descripción | Y2KC Nonvolatile Timekeeping RAM | |
| Fabricantes | Dallas | |
| Logotipo |  |
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DS1742
Y2KC Nonvolatile Timekeeping RAM
FEATURES
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 eight top RAM locations
Century byte register
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
Standard JEDEC bytewide 2k x 8 static RAM
pinout
Quartz accuracy ±1 minute a month @ 25°C,
factory calibrated
PIN ASSIGNMENT
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
GND
1
2
3
4
5
6
7
8
9
10
11
12
24 VCC
23 A8
22 A9
21 WE
20 OE
19 A10
18 CE
17 DQ7
16 DQ6
15 DQ5
14 DQ4
13 DQ3
PIN DESCRIPTION
A0-A10
CE
OE
WE
VCC
GND
DQ0-DQ7
- Address Inputs
- Chip Enable
- Output Enable
- Write Enable
- Power Supply Input
- Ground
- Data Input/Outputs
ORDERING INFORMATION
DS1742-XXX
(5V)
-70 70 ns access
-100 100 ns access
DS1742W-XXX
(3.3V)
-120 120 ns access
-150 150 ns access
DESCRIPTION
The DS1742 is a full function, year 2000-compliant (Y2KC), real-time clock/calendar (RTC) and 2k x 8
non-volatile static RAM. User access to all registers within the DS1742 is accomplished with a bytewide
interface as shown in Figure 1. The Real Time Clock (RTC) information and control bits reside in the
eight uppermost RAM locations. The RTC registers contain century, 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.
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091800
1 page  
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
DS1742
-0.3V to +6.0V
0°C to 70°C
-20°C to +70°C
See J-STD-020A Specification (See Note 7)
* 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
Temperature
0°C to +70°C
VCC
3.3V ± 10% or 5V ± 10%
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
SYMBOL MIN TYP
Logic 1 Voltage All Inputs
VCC = 5V ±10%
VIH 2.2
VCC = 3.3V ±10%
VIH 2.0
Logic 0 Voltage All Inputs
VCC = 5V ±10%
VIL -0.3
VCC = 3.3V ±10%
VIL -0.3
(Over the Operating Range)
MAX UNITS NOTES
VCC +0.3V
VCC +0.3V
V
V
1
1
0.8 V 1
0.6 V 1
DC ELECTRICAL CHARACTERISTICS
(Over the Operating Range; VCC = 5.0V ± 10%)
PARAMETER
SYMBOL MIN TYP MAX UNITS NOTES
Active Supply Current
ICC
15 50 mA 2, 3
TTL Standby Current ( CE =VIH )
CMOS Standby Current
( CE ≥=VCC - 0.2V)
Input Leakage Current
(any input)
ICC1
ICC2
IIL
1
1
-1
3 mA 2, 3
3 mA 2, 3
+1 µA
Output Leakage Current
(any output)
IOL -1
+1 µA
Output Logic 1 Voltage
(IOUT = -1.0 mA)
Output Logic 0 Voltage
(IOUT = +2.1 mA)
VOH
VOL
2.4
0.4
1
1
Write Protection Voltage
VPF 4.25
4.50 V
1
Battery Switch-over Voltage
VSO
VBAT
1, 4
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5 Page 
AC TEST CONDITIONS
Output Load:
100 pF + 1TTL Gate
Input Pulse Levels:
0.0 to 3.0 Volts
Timing Measurement Reference Levels:
Input: 1.5V
Output: 1.5V
Input Pulse Rise and Fall Times: 5 ns
DS1742
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. Data retention time is at 25°C.
6. Each DS1742 has a built-in switch that disconnects the lithium source until VCC is first applied by the
user. The expected tDR is defined as a cumulative time in the absence of VCC starting from the time
power is first applied by the user.
7. 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 to prevent damage to the crystal.
11 of 12
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet DS1742.PDF ] | |
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