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PDF DS1554 Data sheet ( Hoja de datos )
| Número de pieza | DS1554 | |
| Descripción | 256K NV Y2KC Timekeeping RAM | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de DS1554 (archivo pdf) en la parte inferior de esta página. Total 21 Páginas | ||
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www.dalsemi.com
PRELIMINARY
DS1554
256K NV Y2KC Timekeeping RAM
FEATURES
Integrated 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
16 top RAM locations
Century byte register; i.e., Y2K complaint
Totally nonvolatile with over 10 years of
operation in the absence of power
Precision power-on reset
Programmable watchdog timer and RTC alarm
BCD coded 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
PIN ASSIGNMENT
RST
A16
A14
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
15
16
32 VCC
31 NC
30 IRQ/FT
29 WE
28 A13
27 A8
26 A9
25 A11
24 OE
23 A10
22 CE
21 DQ7
20 DQ6
19 DQ5
18 DQ4
17 DQ3
32-PIN ENCAPSULATED PACKAGE
IRQ/FT 1
34
NC
NC
RST
VCC
WE
OE
CE
DQ7
2
3
4
5
6
7
8
9
33
32
31
30
29
28
27
26
DQ6 10
25
DQ5
DQ4
11
12
24
23
DQ3 13
22
DQ2
DQ1
DQ0
14 21
15
16
X1 GND VBAT X2
20
19
GND 17
18
NC
NC
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
34-Pin POWERCAP MODULE BOARD
(USES DS9034PCX POWERCAP)
1 of 21
111999
1 page  
DS1554
BATTERY LONGEVITY
The DS1554 has a lithium power source that is designed to provide energy for the 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 DS1554 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. Each DS1554 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 DS1554 will be much longer than 10 years since no internal battery energy is
consumed when VCC is present.
INTERNAL BATTERY MONITOR
The DS15543 constantly monitors the battery voltage of the internal batter. The Battery Low Flag (BLF)
bit of the Flags Register (B4 of 7FFF0h) is not writable and should always be a 0 when read. If a 1 is ever
present, an exhausted lithium energy source is indicated and both the contents of the RTC and RAM are
questionable.
POWER-ON RESET
A temperature compensated comparator circuit monitors the level of VCC. When VCC falls to the power
fail trip point, the RST signal (open drain) is pulled low. When VCC returns to nominal levels, the
RST signal continues to be pulled low for a period of 40 ms to 200 ms. The power-on reset function is
independent of the RTC oscillator and thus is operational whether or not the oscillator is enabled.
CLOCK OPERATIONS
Table 2 and the following paragraphs describe the operation of RTC, alarm, and watchdog functions.
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5 Page 
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL MIN
Active Supply Current
TTL Standby Current ( CE = VIH )
CMOS Standby Current
( CE ≥=VCC - 0.2V)
Input Leakage Current (any input)
Output Leakage Current
(any output)
Output Logic 1 Voltage
(IOUT = -1.0 mA)
Output Logic 0 Voltage
(IOUT =2.1 mA, DQ0-7 Outputs)
(IOUT =10.0 mA, IRQ /FT and
RST Outputs)
Write Protection Voltage
Battery Switch Over Voltage
ICC
ICC1
ICC2
IIL
IOL
VOH
VOL1
VOL2
VPF
VSO
-1
-1
2.4
2.80
READ CYCLE TIMING DIAGRAM Figure 5
DS1554
(0°C to 70°C; VCC = 3.3V ± 10%)
TYP MAX UNITS NOTES
10 30 mA 2, 3
0.7 3 mA 2, 3
0.7 2 mA 2, 3
+1 µA
+1 µA
V
1
0.4
0.4
2.88
VBAT or
VPF
2.97
V
V
V
V
1
1, 5
1
1, 4
11 of 21
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| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet DS1554.PDF ] | |
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