DS1284 [DALLAS]
Watchdog Timekeeper Chip; 看门狗时钟芯片
| 型号： | DS1284 |
| 厂家： | 
DALLAS SEMICONDUCTOR |
| 描述： | Watchdog Timekeeper Chip |
| 文件： | 总3页 (文件大小：147K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS1284
Watchdog Timekeeper Chip
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
§ Keeps track of hundredths of seconds,
seconds, minutes, hours, days, date of the
month, months, and years; valid leap year
compensation up to 2100
§ Watchdog timer restarts an out-of-control
processor
§ Alarm function schedules real-time related
activities
§ Programmable interrupts and square wave
outputs maintain 28-pin JEDEC footprint
§ All registers are individually addressable via
the address and data bus
VCC
INTB(INTB)
VBAT
RCLR
SQW
OE
A4
GND
1
28
27
INTA
X1
X2
2
3
4
26
25
NC
A5
A4
A3
A2
A1
A0
DQ0
5
6
24
23
4
3
2
1
28 27 26
25
5
A5
VBAT
RCLR
SQW
OE
GND
CE
DQ7
6
24
23
7
8
22
21
7
A3
A2
A1
A0
22
21
20
19
8
CE
DQ7
DQ6
9
10
20
19
9
10
11
11
12
18
17
DQ0
12 13 14 15 16 17 18
DQ1
DQ2
GND
DQ5
DQ4
DQ3
13
14
16
15
DS1284
DS1284
28-Pin PLCC
§ Accuracy is better than ±2 minute/month at
25°C
28-Pin DIP (600-mil)
§ 50 bytes of user NV RAM
PIN DESCRIPTION
§ Optional 28-pin PLCC surface mount package
§ Low-power CMOS circuitry is maintained on
less than 0.5 mA when power is supplied from
battery input
§ Optional industrial temperature range
available on 28-pin PLCC (-40°C to +85°C)
- Interrupt Output A (open drain)
INTA
(INTB) - Interrupt Output B (open drain)
INTB
A0-A5
- Address Inputs
DQ0-DQ7
- Data Input/Output
- Chip Enable
CE
OE
- Output Enable
- Write Enable
WE
VCC
- +5 Volts
GND
NC
- Ground
- No Connection
SQW
X1,X2
VBAT
- Square Wave Output
- 32.768 kHz Crystal Connections
- +3 Volt Battery Input
- RAM Clear
RCLR
DESCRIPTION
The DS1284 Watchdog Timekeeper Chip is a self-contained real-time clock, alarm, watchdog timer, and
interval timer in a 28-pin JEDEC DIP package or a 28-pin PLCC surface mount package. An external
crystal and battery are the only components required to maintain time-of-day and memory status in the
absence of power. For a complete description of operating conditions, electrical characteristics, bus
timing, and pin descriptions other than X1, X2, VBAT, and
data sheet.
, see the DS1286 Watchdog Timekeeper
RCLR
1 of 3
072799
DS1284
PIN DESCRIPTION
X1, X2 - Connections for a standard 32.768 kHz quartz crystal. The internal oscillator circuitry is
designed for operation with a crystal having a specified load capacitance (CL) of 6 pF. The crystal is
connected directly to the X1 and X2 pins. There is no need for external capacitors or resistors. For more
information on crystal selection and crystal layout considerations, please consult Application Note 58,
“Crystal Considerations with Dallas Real Time Clocks.”
VBAT - Battery input for any standard 3-volt lithium cell or other energy source. Battery voltage must be
held between 2.4 and 3.7 volts for proper operation. The nominal write-protect trip point voltage at which
access to registers containing time, watchdog, alarm, and RAM information is denied is set by internal
circuitry as 1.26 x VBAT. A maximum load of 0.5 mA at 25°C in the absence of power should be used to
size the external energy source. The battery should be connected directly to the VBAT pin. A diode must
not be placed in series with the battery to the VBAT pin. Furthermore, a diode is not necessary because
reverse charging current protection circuitry is provided internal to the device and has passed the
requirements of Underwriters Laboratories for UL listing. An optional ground pin is provided for
connection to battery negative. This pin should be grounded but can be left floating.
- The
pin is used to clear (set to logic 1) all 50 bytes of user NV RAM but does not affect
RCLR
RCLR
the registers involved with time, alarm, and watchdog functions. In order to clear the RAM,
must
RCLR
be forced to an input logic 0 (-0. 3 to +0.8 volts) during battery back-up mode when VCC is not applied.
The function is designed to be used via human interface (shorting to ground or by switch) and not
RCLR
be driven with external buffers. This pin is internally pulled up and should be left floating when not in
use.
DS1284Q 28-PIN PLCC WATCHDOG TIMEKEEPER
PKG
DIM
28-PIN
MIN MAX
A IN.
MM
0.300 BSC
7.62
B IN.
MM
D IN.
MM
0.442
17.68
0.480
12.2
0.462
11.73
0.500
12.7
D2 IN.
MM
E IN.
MM
0.390
9.91
0.090
2.29
0.430
10.92
0.120
3.05
E2 IN.
MM
0.390
9.91
0.430
10.92
F IN.
MM
H IN.
MM
0.015
0.38
0.100
2.54
0.020
0.518
0.020
0.518
2 of 3
DS1284
DS1284 28-PIN DIP WATCHDOG TIMEKEEPER
PKG
DIM
28-PIN
MIN
MAX
A IN.
MM
B IN.
MM
C IN.
MM
D IN.
MM
E IN.
MM
F IN.
MM
G IN.
MM
H IN.
MM
1.445
0.530
0.140
0.600
0.015
0.120
0.090
0.625
0.008
0.015
1.470
0.550
0.160
0.625
0.040
0.145
0.110
0.675
0.012
0.022
J IN.
MM
K IN.
MM
3 of 3
相关型号：
DS1284+
Real Time Clock, Volatile, 1 Timer(s), CMOS, PDIP28, 0.600 INCH, ROHS COMPLIANT, PLASTIC, DIP-28
MAXIM
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