DS1384FP-12+ [MAXIM]
Watchdog Timekeeping Controller; 看门狗计时控制器
| 型号： | DS1384FP-12+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Watchdog Timekeeping Controller |
| 文件： | 总18页 (文件大小：485K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DS1384
www.maxim-ic.com
FEATURES
PIN CONFIGURATION
ꢀ Keeps Track of Hundredths of Seconds,
Seconds, Minutes, Hours, Days, Date of the
Month, Months, and Years with Leap Year
Compensation Valid Up to 2100
TOP VIEW
44
34
ꢀ Watchdog Timer Restarts an Out-of-
Control Processor
1
33
INTB
A15
VBAT1
WE
A13
A8
ꢀ Alarm Function Schedules Real-Time
N.C.
A14
A12
A7
Related Activities
DS1384
ꢀ Programmable Interrupts and Square-
Wave Outputs
A6
A9
A11
OE
A10
CE
A5
ꢀ Bytewide RAM-Like Access
ꢀ 50 Bytes of On-Board User RAM
ꢀ Greater Than 10 Years Timekeeping and
Data Retention in the Absence of Power
with Small Lithium Coin Cells
A4
A3
A2
A1
OE
23
11
12
22
ꢀ Supports Up to 128k x 8 of External Static
RAM
MQFP
ꢀ All Timekeeping Registers and On-Board
RAM are Individually Addressable via the
Address and Data Bus
ORDERING INFORMATION
PART
DS1384FP-12
DS1384FP-12+
TEMP RANGE
0°C to +70°C
0°C to +70°C
VOLTAGE (V)
PIN-PACKAGE
44 MQFP
44 MQFP
TOP MARK*
DS1384FP
DS1384FP
5.0
5.0
+ Denotes lead-free/RoHS-compliant device.
* A “+” anywhere on the top mark indicates a lead-free/RoHS-compliant device.
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REV: 112105
DS1384
DETAILED DESCRIPTION
The DS1384 watchdog timekeeping controller is a self-contained real-time clock, alarm, watchdog timer,
and interval timer that provides control of up to 128k x 8 of external low-power CMOS static RAM in a
44-pin quad flat-pack package. An external crystal and battery are the only components required to
maintain time of day and RAM memory contents in the absence of power. Access to all RTC functions
and the external RAM is the same as conventional bytewide SRAM. Data is maintained in the watchdog
timekeeper by intelligent control circuitry, which detects the status of VCC and write protects both
memory and timekeeping functions when VCC is out of tolerance. Timekeeper information includes
hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the
month is automatically adjusted for months with fewer than 31 days, including correction for leap year.
The timekeeper operates in either 12- or 24-hour format with an AM/PM indicator. The watchdog internal
timer provides watchdog alarm windows and interval timing between 0.01 seconds and 99.99 seconds.
The real time alarm provides for preset times of up to one week. All the RTC functions and the internal
50 bytes of RAM reside in the lower 64 bytes of the attached RAM memory map. The externally attached
static RAM is controlled by the DS1384 via the OER and CEO signals.
Automatic backup and write protection for an external SRAM is provided through the VCCO, CEO, and
OER pins. The lithium energy source used to permanently power the real time clock is also used to retain
RAM data in the absence of VCC power through the VCCO pin. The chip enable output to RAM (CEO) and
the output enable to RAM (OER) are controlled during power transients to prevent data corruption. The
DS1384 is a complete one-chip solution in that an external crystal and battery are the only components
required to maintain time of day memory status in the absence of power.
PIN DESCRIPTION
PIN
NAME
FUNCTION
Interrupt Output B (Active High or Low). INTB outputs the alarm
(time of day or watchdog) that is not selected for INTA. This pin is
programmable high or low. Both INTA and INTB/(INTB) are open-
drain outputs. The two interrupts and the internal clock continue to run
regardless of the VCC level. However, it is important to ensure that the
pullup resistors used with the interrupt pins are never pulled up to a
value that is greater than VCC + 0.3V. As VCC falls below
1
INTB/(INTB)
approximately 3.0V, a power-switching circuit turns the lithium
energy source on to maintain the clock and timer data functionality. It
is also required to ensure that during this time (battery-backup mode)
the voltage present at INTA and INTB/(INTB) never exceeds VBAT
.
At all times the current on each should not exceed +2.1mA or -1.0mA.
No Connection
2
3
4
5–12
25
27
28
29
30
33
40
N.C.
A14
A12
A7–A0
A10
A11
A9
Address Bus (Input). The address bus inputs qualified by CE, OE,
WE, and VCC are used to select the on-chip 64 timekeeping/RAM
registers within the memory map of the external SRAM controlled as
nonvolatile storage. When the qualified address bus value is within the
range of 00000H–0003FH, one of the internal registers is selected and
OER remains inactive. When the value is outside the range, OE is
passed through to OER.
A8
A13
A15
A16
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DS1384
PIN
NAME
FUNCTION
Data Bus (Bidirectional). When a qualified address from 00000H–
0003FH is presented to the device, data is passed to or from the on-
13, 14, 15, DQ0, DQ1, DQ2, chip 64 timekeeping/RAM registers via the data bus lines. Data is
17–21
DQ3–DQ7
written on the rising edge of WE when CE is active. If CE is active
without WE, data is read from the device and driven onto the data bus
pins when OE is low.
Ground. DC power input.
16, 41, 44
22
GND
Active-Low RAM Chip-Enable Output. When power is good, the CE
input is passed through to CEO. If VCC is below VPF, CEO remains at
an inactive high level.
CEO
Active-Low RAM Output Enable (Output). When power is good and
the address value is not within the range of 00000H and 0003FH, and
CE is active, the OE input is passed through to OER. If these
conditions are not met, OER remains at an inactive high level.
Active-Low Chip Enable (Input). This signal must be asserted low
during a bus cycle to access the on-chip timekeeping RAM registers,
or to access the external RAM via CEO.
23
24
OER
CE
Active-Low Output Enable (Input). This signal identifies the time
period when either the RTC or the external SRAM drives the bus with
read data, provided that CE is valid with WE disabled. When one of
the 64 on-chip registers is selected during a read cycle, the OE is the
enable signal for the DS1384 output buffers and the data bus is driven
with read data. When the external RAM is selected during a read
cycle, the OE signal is passed through to the OER pin so that read data
is driven by the external SRAM.
Active-Low Write Enable (Input). This signal identifies the time
period during which data is written to either the on-chip registers or to
an external SRAM location. When one of the on-chip 64 registers is
addressed, data is written to the selected register on the rising edge of
WE.
26
31
OE
WE
Battery Inputs for Any Standard 3V Lithium Cell or Other Energy
Source. Battery voltage must be held between 2.4V and 4V for proper
operation. In the absence of power, the DS1384 has a maximum load
of 0.5µA at +25°C. This should be added to the amount of current
drawn from the external RAM in standby mode at +25°C to size the
external energy source. The DS1384 samples VBAT1 and VBAT2 and
always selects the battery with the higher voltage. If only one battery
is used, the unused battery input must be grounded.
32, 34
VBAT1, VBAT2
Power-Fail Signal (Output, Active Low when VWP Occurs). High state
occurs tREC after power-up and VCC ≥ 4.5V.
35
36
PFO
Square-Wave Output. This pin can be programmed to output a
1024Hz square-wave signal. When the signal is turned off, the pin is
high impedance.
Switched DC Power for SRAM (Output). This pin is connected to VCC
when VCC voltage is above VSO (the greater of VBAT1 or VBAT2). When
VCC voltage falls below this level, VCCO is connected to the higher
voltage battery pin.
SQW
37
VCCO
3 of 18
DS1384
PIN
NAME
FUNCTION
DC Power Input. DC operating voltage is provided to the device on
this pin. VCC is the +5V input.
38
VCC
Active-Low Interrupt Output A. INTA can be programmed as a time-
of-day alarm or as a watchdog alarm. (INTB becomes the alternate
function). INTA can also be programmed to output either a pulse or a
level.
39
INTA
Connections for Standard 32.768kHz Quartz Crystal. When ordering,
request a load capacitance (CL) of 6pF. The internal oscillator circuitry
is designed for operation with a crystal having a specified load
capacitance of 6pF. For more information on crystal selection and
crystal layout considerations, refer to Application Note 58: Crystal
Considerations with Dallas Real Time Clocks.
42, 43
X1, X2
ADDRESS DECODING
The DS1384 accommodates 17 address lines, which allows direct connection of up to 128k bytes of static
RAM. The lower 14 bytes of RAM, regardless of the density used, will always contain the timekeeping,
alarm, and watchdog registers. The 14 clock registers reside in the lower 14 RAM locations without
conflict by inhibiting the OER (output enable RAM) signal during clock access. Since the watchdog
timekeeping chip actually contains 64 registers (14 RTC and 50 user RAM), the lower 64 bytes of any
attached memory resides within the DS1384. However, the RAM’s physical location is transparent to the
user and the memory map looks continuous from the first clock address to the upper most attached RAM
address.
OPERATION—READ CYCLE
The DS1384 executes a read cycle whenever WE is inactive (high) and CE and OE are active (low). The
unique address specified by the address inputs (A0-A16) defines which of the on-chip 64 RTC/RAM or
external SRAM locations is to be accessed. When the address value presented to the DS1384 is in the
range of 00000H through 0003FH, one of the 64 on-chip registers will be selected and valid data will be
available to the eight data output drivers within tACC (access time) after the address input signal is stable,
providing that the CE and OE access times are also satisfied. If they are not, then data access must be
measured from the latter occurring signal (CE or OE) and the limiting parameter is either tCO for CE or
tOE for OE rather than the address access time. When one of the on-chip registers is selected for read, the
OER signal will remain inactive throughout the read cycle.
When the address value presented to the DS1384 is in the range of 00040H through 1FFFFH, an external
SRAM location will be selected. In this case the OE signal will be passed to the OER pin, with the
specified delay times of tAOEL or tOERL
.
OPERATION—WRITE CYCLE
The DS1384 is in the write mode whenever the WE (Write Enable) and CE (Chip Enable) signals are in
the active (low) state after the address inputs are stable. The latter occurring falling edge of CE or WE
will determine the start of the write cycle. The write cycle is terminated by the earlier rising edge of CE
or WE. All address inputs must be kept valid throughout the write cycle. WE must return to the high state
for a minimum recovery state (tWR) before another cycle can be initiated. Data must be valid on the data
bus with sufficient Data Set Up (tDS) and Data Hold Time (tDH) with respect to the earlier rising edge of
CE or WE. The OE control signal should be kept inactive (high) during write cycles to avoid bus
4 of 18
DS1384
contention. However, if the output bus has been enabled (CE and OE active), then WE will disable the
outputs in tWEZ from its falling edge.
When the address value presented to the DS1384 during the write is in the range of 00000H through
0003FH, one of the 64 on-chip registers will be selected and data will be written into the device.
When the address value presented to the DS1384 during the write is in the range of 00040H through
1FFFFH, an external SRAM location will be selected.
DATA RETENTION MODE
When VCCI is within nominal limits (VCC > 4.5V) the DS1384 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 external RAM is blocked from access. This is
accomplished internally by inhibiting access to the clock registers via the CE signal. At this time the
power fail output signal (PFO) is driven active and will remain active until VCC returns to nominal levels.
External RAM access is inhibited in a similar manner by forcing CEO to high level. This level is within
0.2 volts of the VCCI input. CEO will remain at this level as long as VCCI remains at an out-of-tolerance
condition. When VCCI falls below the level of the battery (VBAT1 or VBAT2), power input is switched from
the VCCI pin to the VBAT pin and the clock registers are maintained from the attached battery supply.
External RAM is also powered by the VBAT input when VCCI is below VBAT pin through the VCCO pin. The
VCCO pin is capable of supplying 100µA of current to the attached memory with less than 0.3V drop
under this condition. On power-up, when VCCI returns to in-tolerance conditions, write protection
continues for 150ms by inhibiting CEO. The PFO signal also remains active during this time. The
DS1384 is capable of supporting two batteries which are used in a redundant fashion for applications
which require added reliability or increased battery capacity. When two batteries are used, the higher of
the two is selected for use. A selected battery will remain as backup supply until it is significantly below
the other. When the selected battery voltage falls below the alternate battery by about 0.6V, the alternate
battery is selected and then becomes the backup supply. This switching occurs transparently to the user
and continues until both batteries are exhausted. When only a single battery is required, both battery
inputs can be connected together. However, a more effective method of using a single battery supply is to
ground the unused battery input. When using a single battery, VBAT1 is the preferred input.
WATCHDOG TIMEKEEPER REGISTERS
The DS1384 Watchdog Timekeeper Controller has 14 internal registers, which are 8 bits wide and
contain all of the Timekeeping, Alarm, Watchdog, Control, and Data information. The Clock, Calendar,
Alarm and Watchdog Registers are memory locations, which contain external (user accessible) and
internal copies of the data. The external copies are independent of internal functions except that they are
updated periodically by the simultaneous transfer of the incremented internal copy (see Figure 1). The
Command Register bits are affected by both internal and external functions. This register will be
discussed later. The 50 bytes of RAM registers are accessed from the external address and data bus and
reside or overlay external static RAM. Registers 0, 1, 2, 4, 6, 8, 9 and A contain time of day and date
information (see Figure 2). Time of day information is stored in BCD. Registers 3, 5, and 7 contain the
time of day alarm information. Time of day alarm information is stored in BCD. Register B is the
Command Register and information in this register is binary. Register C and D are the Watchdog Alarm
Registers and information, which is stored in these two registers, is in BCD. Registers 0000EH through
register 0003FH are on-chip user bytes and can be used to contain data at the user’s discretion.
5 of 18
DS1384
Figure 1. DS1384 Block Diagram
6 of 18
DS1384
Figure 2. DS1384 Watchdog Timekeeper Registers
7 of 18
DS1384
Table 1. Time Of Day Alarm Mask Bits
REGISTER
DESCRIPTION
MINUTES
HOURS
DAYS
1
0
0
0
1
1
0
0
1
1
1
0
Alarm Once Per Minute
Alarm When Minutes Match
Alarm When Hours And Minutes Match
Alarm When Hours, Minutes, And Days Match
Note: any other bit combinations of mask bit settings produce illogical operation.
TIME-OF-DAY REGISTERS
Registers 0, 1, 2, 4, 6, 8, 9 and A contain time of day data in BCD. Ten bits within these eight registers
are not used and will always read 0 regardless of how they are written. Bits 6 and 7 in the Months
Register (9) are binary bits.
When set to logical 0, EOSC (bit 7) enables the real-time clock oscillator. This bit will normally be turned
on by the user during device initialization. However, the oscillator can be turned on and off as necessary
by setting this bit to the appropriate level.
Bit 6 of this same byte controls the square wave output (pin 24). When set to logical 0, the square wave
output pin will output a 1024 Hz square wave signal. When set to logic 1 the square wave output pin is in
a high impedance state.
Bit 6 of the Hours Register is defined as the 12- or 24-Hour Select Bit. When set to logic 1, the 12-hour
format is selected. In the 12-hour format, bit 5 is the AM/ PM bit with logical one being PM. In the 24-
hour mode, bit 5 is the second 10-hour bit (20-23 hours). The time of day registers are updated every 0.01
seconds from the real time clock, except when the TE bit (bit 7 of register B) is set low or the clock
oscillator is not running.
The preferred method of synchronizing data access to and from the Watchdog Timekeeper is to access the
Command Register by doing a write cycle to address location 0B and setting the TE bit (Transfer Enable
bit) to a logic 0. This will freeze the external time of day registers at the present recorded time allowing
access to occur without danger of simultaneous update. When the watch registers have been read or
written a second write cycle to location 0B, setting the TE bit to a logic 1, will put the time of day
registers back to being updated every 0.01 second. No time is lost in the real time clock because the
internal copy of the time of day register buffers are continually incremented while the external memory
registers are frozen. An alternate method of reading and writing the time of day registers is to ignore
synchronization. However, any single read may give erroneous data as the real time clock may be in the
process of updating the external memory registers as data is being read.
The internal copies of seconds through years are incremented and Time of Day Alarm is checked during
the period that hundredths of seconds reads 99 and are transferred to the external register when
hundredths of seconds roll from 99 to 00. A way of making sure data is valid is to do multiple reads and
compare. Writing the registers can also produce erroneous results for the same reasons. A way of making
sure that the write cycle has caused proper update is to do read verifies and re-execute the write cycle if
data is not correct. While the possibility of erroneous results from reads and write cycles has been stated,
it is worth noting that the probability of an incorrect result is kept to a minimum due to the redundant
structure of the Watchdog Timekeeper.
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DS1384
TIME-OF-DAY ALARM REGISTERS
Registers 3, 5, and 7 contain the time of day alarm registers. Bits 3, 4, 5, and 6 of register 7 will always
read 0 regardless of how they are written. Bit 7 of registers 3, 5, and 7 are mask bits (Table 1). When all
of the mask bits are logic 0, a time of day alarm will only occur when registers 2, 4, and 6 match the
values stored in registers 3, 5, and 7. An alarm will be generated every day when bit 7 of register 7 is set
to a logic 1. Similarly, an alarm is generated every hour when bit 7 of registers 7 and 5 is set to a logic 1.
When bit 7 of registers 7, 5, and 3 is set to a logic 1, an alarm will occur every minute when register 1
(seconds) rolls from 59 to 00.
Time of day alarm registers are written and read in the same format as the time of day registers. The time
of day alarm flag and interrupt is always cleared when alarm registers are read or written.
WATCHDOG ALARM REGISTERS
Registers C and D contain the time for the Watchdog Alarm. The two registers contain a time count from
00.01 seconds to 99.99 seconds in BCD. The value written into the Watchdog Alarm Registers can be
written or read in any order. Any access to Register C or D will cause the Watchdog Alarm to reinitialize
and clears the Watchdog Flag Bit and the Watchdog Interrupt Output. When a new value is entered or the
Watchdog Registers are read, the Watchdog Timer will start counting down from the entered value to 0.
When 0 is reached, the Watchdog Interrupt Output will go to the active state. The Watchdog Timer
Countdown is interrupted and reinitialized back to the entered value every time either of the registers are
accessed. In this manner, controlled periodic accesses to the Watchdog Timer can prevent the Watchdog
Alarm from ever going to an active level. If access does not occur, countdown alarm will be repetitive.
The Watchdog Alarm Registers always read the entered value. The actual count down register is internal
and is not readable. Writing registers C and D to 0 will disable the Watchdog Alarm feature.
COMMAND REGISTER
Address location 0Bh is the Command Register where mask bits, control bits and flag bits reside. The
operation of each bit is as follows:
Bit 7: TE (Transfer Enable). This bit when set to a logic 0 will disable the transfer of data between
internal and external clock registers. The contents in the external clock registers are now frozen and reads
or writes will not be affected with updates. This bit must be set to a logic 1 to allow updates.
Bit 6: IPSW (Interrupt Switch). When set to a logic 1, INTA is the Time of Day Alarm and
INTB/(INTB) is the Watchdog Alarm. When set to logic 0, this bit reverses the output pins. INTA is now
the Watchdog Alarm output and INTB /(INTB) is the Time of Day Alarm output.
Bit 5: IBH/LO (Interrupt B Sink or Source Current). When this bit is set to a logic 1 and VCC is
applied, INTB /(INTB) will source current (see DC characteristics IOH). When this bit is set to a logic 0,
INTB will sink current (see DC characteristics IOL).
Bit 4: PU/LVL (Interrupt Pulse Mode or Level Mode). This bit determines whether both interrupts
will output a pulse or level signal. When set to a logic 0, INTA and INTB /(INTB) will be in the level
mode. When this bit is set to a logic 1, the pulse mode is selected and INTA will sink current for a
minimum of 3 ms and then release. INTB /(INTB) will either sink or source current, depending on the
condition of bit 5, for a minimum of 3 ms and then release.
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DS1384
Bit 3: WAM (Watchdog Alarm Mask). When this bit is set to a logic 0, the Watchdog Interrupt output
will be activated. The activated state is determined by bits 1,4,5, and 6 of the Command Register. When
this bit is set to a logic 1, the Watchdog interrupt output is deactivated.
Bit 2: TDM (Time-of-Day Alarm Mask). When this bit is set to a logic 0, the Time of Day Alarm
Interrupt output will be activated. The activated state is determined by bits 0, 4, 5, and 6 of the Command
Register. When this bit is set to a logic 1, the Time of Day Alarm interrupt output is deactivated.
Bit 1: WAF (Watchdog Alarm Flag). This bit is set to a logic 1 when a watchdog alarm interrupt
occurs. This bit is read-only.
The bit is reset when any of the Watchdog Alarm registers are accessed.
When the interrupt is in the pulse mode (see bit 4 definition), this flag will be in the logic 1 state only
during the time the interrupt is active.
Bit 0: TDF (Time-of-Day Flag). This is a read-only bit. This bit is set to a logic 1 when a time of day
alarm has occurred. The time the alarm occurred can be determined by reading the Time of Day Alarm
registers. This bit is reset to a logic 0 state when any of the Time of Day Alarm registers is accessed.
When the interrupt is in the pulse mode (see bit 4 definition), this flag will be in the logic 1 state only
during the time the interrupt is active.
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DS1384
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground……………………………………………..-0.3V to +7.0V
Operating Temperature Range………………………………………………………………..0°C to +70°C
Storage Temperature Range………………………………………………………………..-20°C to +70°C
Soldering Temperature………………………………………….See IPC/JEDEC J-STD-020 Specification
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.
RECOMMENDED DC OPERATING CONDITIONS
(TA = 0°C to +70°C)
PARAMETER
SYMBOL
VCC
MIN
4.5
TYP
MAX
5.5
UNITS
NOTES
Supply Voltage
V
V
V
V
1
Logic 1 Voltage All Inputs
Logic 0 Voltage All Inputs
Battery Input Voltage
VIH
2.0
VCC + 0.3
0.8
VIL
VBAT
-0.3
2.4
4.0V
DC ELECTRICAL CHARACTERISTICS
(VCC = 5V ±10%, TA = 0°C to 70°C.)
PARAMETER
Average VCC Power-
Supply Current
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
ICC1
7
15
mA
2, 3
TTL Standby Current
(CE = VIH)
ICC2
ICC3
2
1
5
3
mA
mA
2, 3
2, 3
CMOS Standby Current
(CE < VCC - 0.2V)
Input Leakage Current
(Any Input)
IIL
IIO
1
+1
+1
µA
µA
V
Output Leakage Current
Output Logic 1 Voltage
(IOH = -1.0mA)
-1
VOH
2.4
Output Logic 0 Voltage
(IOH = +2.1mA)
VOL
0.4
V
Output Voltage
VCCO1
ICCO1
VPF
VCC - 0.3
V
mA
V
4
4
5
Output Current
85
4.5
Write Protection Voltage
4.0
VBAT
-0.3
4.25
Output Voltage
VCCO2
V
6
6
Output Current
Battery Leakage OSC ON
Battery Leakage OSC OFF
ICCO2
IBAT1
IBAT2
100
500
100
µA
nA
nA
VBAT1
,
Switchover Voltage
VSO
V
VBAT2
11 of 18
DS1384
AC ELECTRICAL CHARACTERISTICS
(VCC = 5.0V ±10%, TA = 0°C to +70°C.)
PARAMETER
SYMBOL
tRC
MIN
TYP
MAX
UNITS
ns
NOTES
Read Cycle Time
120
Address Access Time
CE Access Time
tACC
120
120
40
60
40
ns
tCO
ns
CE Data Off Time
tCEZ
ns
Output Enable Access Time
Output Enable Data Off Time
Output Enable to DQ Low-Z
CE to DQ Low-Z
tOE
ns
tOEZ
tOEL
tCEL
ns
5
10
5
ns
ns
Output Hold from Address
CE to CEO Low or High
OE Low to OER Low
A0–A16 ≥ 00040h
tOH
ns
tCEPD
25
20
20
50
ns
tOERL
tRO
ns
ns
ns
OE High to OER High Time
Address 00040h–1FFFFh to OER
tAOEL
Low
Address 00000h–0003Fh to OER
High
tAOEH
40
ns
Write Cycle Time
tWC
tAW
tCEW
tAH
120
0
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
Address Setup Time
CE Pulse Width
120
10
80
Address Hold from End of Write
Write Pulse Width
tWP
CE Data Off Time
tCEZ
tWEZ
tWR
tDS
40
40
WE Data Off Time
WE or CE Inactive Time
Data Setup Time
10
45
0
Data Hold Time High
INTA and INTB Pulse Width
tDH
tIPW
3
AC TEST CONDITIONS
Input Levels: 0V to 3V
Transition Times: 5ns
12 of 18
DS1384
CAPACITANCE
(TA = +25°C)
PARAMETER
Capacitance on All Pins
(Except DQ)
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
CI
7
15
pF
Capacitance on DQ Pins
CDQ
7
15
pF
AC ELECTRICAL CHARACTERISTICS
(TA = 0°C to +70°C)
PARAMETER
CE at VIH before Power-
Down
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
tPD
0
µs
VPF (Max) to VPF (Min)
tF
300
10
µs
µs
V
CC Fall Time
VPF (Min) to VSO VCC Fall
Time
tFB
VPF (Min) to VPF (Max)
tR
0
µs
ms
VCC Rise Time
Power-Up
tREC
tDR
10
10
150
Expected Data Retention
years
7
Time (Oscillator On)
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DS1384
READ CYCLE TIMING—RTC AND EXTERNAL SRAM CONTROL SIGNALS
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DS1384
OER TIMING WHEN SWITCHING BETWEEN LOWER MEMORY
(00000h–0003Fh) AND UPPER MEMORY (00040h–1FFFFh)
WRITE CYCLE TIMING—RTC AND EXTERNAL SRAM CONTROL SIGNALS
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DS1384
POWER-UP TIMING DIAGRAM
POWER-DOWN TIMING DIAGRAM
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DS1384
INTERRUPT OUTPUTS PULSE MODE TIMING DIAGRAM (See Notes 8 and 9)
NOTES:
1) All voltages are referenced to ground.
2) Typical values are at +25°C and nominal supplies.
3) Outputs are open.
4) Value for voltage and currents is from the VCCI input pin to the VCCO pin.
5) Write protection trip point occurs during power fail prior to switchover from VCC to VBAT
.
6) Value for voltage and currents is from the VBAT input pin to the VCCO pin.
7) Data retention time depends on the size of battery selected and the amount of current demanded by
the static RAM in backup mode. The battery capacity (mA • hr) to achieve a tDR of 10 years is given
by the formula: C = (IBAT1 + IRAM) x 24 x 365 x 10, where IRAM is the standby current of the static
RAM at the battery voltage. For the DS1384 chip alone, a standard 48mAh lithium cell battery will
provide greater than 10 years of data retention in the absence of power.
8) Applies to both interrupt pins when the alarms are set to pulse.
9) Interrupt output occurs within 100ns of the alarm condition existing.
OUTPUT LOAD
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DS1384
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.)
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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.
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