DS1501WE/T&R - Maxim - Product.Live

DS1501/DS1511

Y2K-Compliant Watchdog Real-Time Clocks

GENERAL DESCRIPTION

The DS1501/DS1511 are full-function, year 2000-

compliant real-time clock/calendars (RTCs) with an

RTC alarm, watchdog timer, power-on reset, battery

monitors, 256 bytes NV SRAM, and a 32.768kHz

output. User access to all registers within the

DS1501/DS1511 is accomplished with a byte-wide

interface, as shown in Figure 8. The RTC registers

contain century, year, month, date, day, hours,

minutes, and seconds data in 24-hour binary-coded

decimal (BCD) format. Corrections for day of month

and leap year are made automatically.

APPLICATIONS

Remote Systems

Battery-Backed Systems

Telecom Switches

Office Equipment

Consumer Electronics

Pin Configurations and T y pical Operating Circuit appear at

end of data sheet.

FEATURES

 BCD-Coded Century, Year, Month, Da te, Day,

Hours, Minutes, and Seconds with Automatic

Leap-Year Compensation Valid Up to the Year

2100

 Programmable Watchdog Timer and RTC

Alarm

 Century Register; Y2K-Compliant RTC

 +3.3 (W) or +5V (Y) Opera tion

 Precision Power-On Reset

 Power-Control Circuitry Support System

Power-On from Date/Day/Time Alarm or Key

Closure/Modem-Detect Signal

 256 Bytes Battery-Backed SRAM

 Auxiliary Battery Input

 Accuracy of DS151 1 Better than ±1

Minute/Month at +25°C

 Day-of-Wee k/ Date Alarm Register

 Crystal Select Bit Allo w RTC to Operate with

6pF or 12.6pF Crystal (DS1501)

 Battery Voltage-Level Indicator Flags

 Available as Chip (DS1501) or Stand-Alone

Encapsulated DIP Module with Embedded

Battery and Crystal (DS1511)

 Underwriters Laboratories (UL) Recognized

ORDERING INFORMATION

PART VOLTAGE (V) TEMP RANGE PIN-PACKAGE TOP MARK*

DS1501W+ 3.3

0°C to +70°C 28 DIP (0.600) DS1501W

DS1501WE+ 3.3

0°C to +70°C 28 TSOP DS1501WE

DS1501WEN+ 3.3

-40°C to +85°C 28 TSOP DS1501WEN

DS1501WEN+T&R 3.3 -40°C to +85°C 28 TSOP/Tape & Reel DS1501WEN

DS1501WE+T&R 3.3 0°C to +70°C 28 TSOP/Tape & Reel DS1501WE

+Denotes a lead(Pb)-free/RoHS-compliant package.

*A “+” anywhere on the top mark denotes a lead(Pb)-free device. An N or IND denotes an industrial temperature device.

Ordering Information continued at end of data sheet.

1 of 22 REV: 010909

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.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

2 of 22

ABSOLUTE MAXIMUM RATINGS

Voltage Range on Any Pin Relative to Ground……………………………………… ……………..……....-0.5V to +6.0V

Operating Temperature Range, DS1501………………………………………………..-40°C to +85°C (Note 1)

Operating Temperature Range, DS1511 ………………………………………… …………………….……..0°C to +70°C

Storage Temperature Range, DS1501…………………...…………………………………....-55°C to +125°C

Storage Temperature Range, DS1511………………………………………………………………….…..-40°C to +70°C

Soldering Temperature (DIP, EDIP Module)…..………...….+260°C lead temperature for 10 seconds (max) (Note 2)

Soldering Temperature (SO, TSOP)…….………….…..See IPC/JEDEC J-STD-020 for surface-mount devices

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only,

and functional operation of the device at these or any other conditions beyond thos e indicated in the operational sections of t he specifications is

not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device reliability.

RECOMMENDED DC OPERATING CONDITIONS

(VCC = 3.3V or 5V ±10%, TA = 0°C to +70°C; VCC = 3.3V or 5V ±10%, TA = -40°C to +85°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

5V (Y) 4.5 5.0 5.5

Power Supply Voltage (Note 3) VCC 3.3V (W) 3.0 3.3 3.6 V

Y 2.2 VCC + 0.3

Logic 1 Voltage All Inputs (Note 3) VIH W 2.0 VCC + 0.3 V

Pullup Voltage, IRQ, PWR, and

RST Outputs (Note 3) VPU 5.5 V

Y -0.3 +0.8

Logic 0 Voltage All Inputs (Note 3) VIL W -0.3 +0.6

Battery Voltage (Note 3) VBAT 2.5 3.0 3.7 V

Y 2.5 3.0 5.3

Auxiliary Battery Voltage (Note 3) VBAUX W 2.5 3.0 3.7

DC ELECTRICAL CHARACTERISTICS

(VCC = 3.3V or 5V ±10%, TA = 0°C to +70°C; VCC = 3.3V or 5V ±10%, TA = -40°C to +85°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Y 15

Active Supply Current (Note 4) ICC W 10

Y 5

TTL Standby Current (CE = VIH) ICC1 W 4

Y 5

CMOS Standby Current

(CE = VCC - 0.2V) ICC2 W 4

Input Leakage Current (Any Input) IIL -1 +1 μA

Output Leakage Current (Any Output) IOL -1 +1 μA

Output Logic 1 Voltage

(IOUT = -1.0mA) VOH (Note 3) 2.4 V

VOL1 (Note 3) 0.4 V

Output Logic 0 Voltage (IOUT = 2.1mA,

DQ0–7; IOUT = 5.0mA, IRQ, IOUT =

7.0mA, PWR and RST) VOL2 (Notes 3, 5) 0.4 V

Y 2.0

Battery Low, Flag Trip Point (Note 2) VBLF W 1.9

Y 4.20 4.50

Power-Fail Voltage (Note 2) VPF W 2.75 2.97

Battery Switchover Voltage (Notes 3, 6) VSO VBAT,

VBAUX,

or VPF V

Battery Leakage Current ILKG 100 nA

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

3 of 22

DC ELECTRICAL CHARACTERISTICS

(VCC = 0V; TA = 0°C to +70°C; VCC = 0V, TA = -40°C to +85°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Battery Current, BB32 = 0, EOSC = 0 IBAT1 (Note 7) 0.27 1.0

μA

Battery Current, BB32 = 0, EOSC = 1 IBAT2 (Note 7) 0.01 0.1

μA

VBAUX Current BB32 = 1, SQW Open IBAUX (Note 7) 2

μA

CRYSTAL SPECIFICATIONS*

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Nominal Frequency fO 32.768 kHz

Series Resistance ESR 45

kΩ

Load Capacitance CL 6/12.5 pF

*The crystal, traces, and crystal input pins should be isolated from RF generating signals. Refer to Application Note 58: Crystal Considerations

for Dallas Real-Time Clocks for additional specifications.

AC OPERATING CHARACTERISTICS

(VCC = 5V ±10%, TA = 0°C to +70°C; VCC = 5V ±10%, TA = -40°C to +85°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Read Cycle Time tRC 70 ns

Address Access Time tAA 70 ns

CE to DQ Low-Z tCEL (Note 8) 5 ns

CE Access Ti me tCEA 70 ns

CE Data-Off Time tCEZ (Note 8) 25 ns

OE to DQ Low-Z (0°C to +85°C) tOEL (Note 8) 5 ns

OE to DQ Low-Z (-40°C to 0°C) tOEL (Note 8) 2 ns

OE Access Time tOEA 35 ns

OE Data-Off Time tOEZ (Note 8) 25 ns

Output Hold from Address tOH 5 ns

Write Cycle Time tWC 70 ns

Address Setup Time tAS 0 ns

WE Pulse Width tWEW 50 ns

CE Pulse Width tCEW 55 ns

Data Setup Time tDS 30 ns

Data Hold Time tDH 5 ns

Address Hold Time tAH 0 ns

WE Data-Off Time tWEZ (Note 8) 25 ns

Write Recovery Time tWR 15 ns

Pulse Width, OE, WE, or CE High PWHIGH 20 ns

Pulse Width, OE, WE, or CE Low PWLOW 70 ns

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

4 of 22

AC OPERATING CHARACTERISTICS

(VCC = 3.3V ±10%, TA = 0°C to +70°C; VCC = 3.3V ±10%, TA = -40°C to +85°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Read Cycle Time tRC 120 ns

Address Access Time tAA 120 ns

CE to DQ Low-Z tCEL (Note 8) 5 ns

CE Access Ti me tCEA 120 ns

CE Data Off Time tCEZ (Note 8) 40 ns

OE to DQ Low-Z (0°C to +85°C) tOEL (Note 8) 5 ns

OE to DQ Low-Z (-40°C to 0°C) tOEL (Note 8) 2 ns

OE Access Time tOEA 100 ns

OE Data-Off Time tOEZ (Note 8) 35 ns

Output Hold from Address tOH 5 ns

Write Cycle Time tWC 120 ns

Address Setup Time tAS 0 ns

WE Pulse Width tWEW 100 ns

CE Pulse Width tCEW 110 ns

Data Setup Time tDS 80 ns

Data Hold Time tDH 5 ns

Address Hold Time tAH 5 ns

WE Data-Off Time tWEZ (Note 8) 40 ns

Write Recovery Time tWR 15 ns

Pulse Width, OE, WE, or CE High PWHIGH 40 ns

Pulse Width, OE, WE, or CE Low PWLOW 100 ns

Figure 1. Read Cycle Timing

tRC

tCEA

tOEA

CEL

tOEL

tOH

tOEZ

VALID

DQ0-DQ7

A0–A4

tCEZ

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

5 of 22

Figure 2. Write Cycle Timing, Write-Enable Controlled

tWC

tAH

tDS

tWEZ tDH

tWR

DATA INPUT

DQ0–DQ7

A0–A4

DATA OUTPUT DATA INPUT

tWEW

VALID VALID

Figure 3. Write Cycle Timing, Chip-Enable Controlled

tWC

tDS

tAS

D A T A IN P UT

DQ0-DQ7

A0-A4

DATA INPUT

tCEW

VALID VALID

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

6 of 22

Figure 4. Burst Mode Timing Waveform

A0–A4

DQ0–DQ7

E, OR

13h

PWHIGH

PWLOW

POWER-UP/DOWN CHARACTERISTICS

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

tPF 0 μs

CE or WE at VIH Before Power-Fail

VCC Fall Time: VPF(MAX) to VPF(MIN) t

F 300 μs

VCC Fall Time: VPF(MIN) to VSO t

FB 10 μs

VCC Rise Time: VPF(MIN) to VPF(MAX) t

R 0 μs

tREC 35 200 ms

VPF to RST High

(TA = +25°C) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Expected Data-Retention Time

(Oscillator On) tDR (Note 9) 10 Years

CAPACITANCE

(TA = +25°C) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Capacitance on All Input Pins CIN 10 pF

Capacitance on IRQ, PWR, RST, and DQ

Pins CIO 10 pF

AC TEST CONDITIONS INPUT PULSE

LEVELS TIMING MEASUREMENT

REFERENCE LEVELS INPUT PULSE RISE

AND FALL TIMES

OUTPUT LOAD

(Y) 50pF + 1TTL Gate Input: 1.5V

0V to 3.0V for 5V

operation Output: 1.5V 5ns

(W) 25pF + 1 TTL Gate

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

7 of 22

Figure 5. 3.3V Power-Up/Down Waveform Timing

Figure 6. 5V Power-Up/Down Waveform Timing

Warning: Under no circumstances are negative undershoots, of any amplitude, allowed when

device is in battery-backup mode.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

8 of 22

WAKEUP/KICKSTART TIMING

(TA = +25°C) (Figure 7)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Kickstart-Input Pulse Width tKSPW 2 μs

Wakeup/Kickstart Power-On Timeout tPOTO (Note 10) 2 s

Note: Time intervals shown above are referenced in Wakeup/Kickstart.

Figure 7. Wakeup/Kickstart Timing Diagram

tKSPW

tPOTO

VCC

CONDITION:

VPF VBAT

<VPF

VBAT

VPF

VCC

CONDITION:

VBAT

VPF >

TDF/KSF

(INTERNAL)

VIL

VIH

HI-Z

____

IRQ

VIL

VIH

HI-Z

____

PWR

VIH

VIL

___

12345

INTERVALS

Note 1: Limits at -40°C are not production tested and are guaranteed by design.

Note 2: RTC 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-sold cleaning with water-washing techniques is acceptable,

provided that ultrasonic vibration is not used to prevent damage to the crystal.

Note 3: Voltage referenced to ground.

Note 4: Outputs are open.

Note 5: The IRQ, PWR, and RST outputs are open drain.

Note 6: If VPF is less than VBAT and VBAUX, the device power is switched from VCC to the greater of VBAT or VBAUX when VCC drops below VPF. If VPF

is greater than VBAT and VBAUX, the device power is switched from VCC to the greater of VBAT or VBAUX when VCC drops below the greater

of VBAT or VBAUX.

Note 7: VBAT or VBAUX current. Using a 32,768Hz crystal connected to X1 and X2.

Note 8: These parameters are sampled with a 5pF load and are not 100% tested.

Note 9: tDR is the amount of time that the internal battery can power the internal oscillator and internal registers of the DS1511.

Note 10: If the oscillator is not enabled, the startup time of the oscillator after VCC1 is applied will be added to the wakeup/kickstart timeout.

Note 11: Typical values are at +25°C, nominal (active) supply, unless otherwise noted.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

9 of 22

PIN DESCRIPTION

DIP, SO EDIP TSOP NAME FUNCTION

1 1 8

PWR Active-Low Power-On Output (Open Drain). This output, if used, is normally

connected to power-supply control circuitry. This pin requires a pullup resistor

connected to a positive supply to operate correctly.

2, 3 — 9, 10 X1, X2

Connections for Standard 32.768kHz Quartz Cr ystal. For greatest accuracy, the

DS1501 must be used with a crystal that has a specified load capacitance of either

6pF or 12.5pF. The crystal select (CS) bit in control register B is used to select

operation with a 6pF or 12.5pF crystal. The crystal is attached directly to the X1 and

X2 pins. There is no need for external capacitors or resistors. An external 32.768kHz

oscillator can also drive the DS1501. In this configuration, the X1 pin is connected to

the external oscillator signal and the X2 pin is floated. For more information about

crystal selection and crystal layout considerations, refer to Applicatio n Note 58:

Crystal Conside r ations with Dallas Real-Time Clocks. See Figur e 9. An enable bit in

the month register controls the oscillator. Oscillator startup time is highly dependent

upon crystal characteristics, PC board leakage, and layout. High ESR and excessive

capacitive loads are the major contributors to long startup times. A circuit using a

crystal with the recommended characteristics and proper layout usually starts w ithin

one second.

4 4 11

RST Active-Low Reset Output. (Open Drain). This output, if used, is normally connected

to a microprocessor-reset input. This pin requires a pull up resistor connected to a

positive supply to operate correctly. When RST is active, the device is not accessible.

5 5 12

IRQ Active-Low Interrupt Output (Open Drain). This output, if used, is normally connected

to a microprocessor interrupt input. This pin requires a pullup resistor connected to a

positive supply to operate correctly.

6–10 6–10 13–17 A4–A0 Address Inputs. Selects one of 17 register locations.

11–13,

15–19 11–13,

15–19 18–20,

22–26 DQ0–DQ7 Data Input/Output. I/O pins for 8-bit parallel data transfer.

14, 21 14 21, 28 GND

Ground. DC power is applied to the device on these pins. VCC is the positive terminal.

When power is applied within the normal limits, the device is fully accessible and

data can be written and read. When VCC drops below the normal limits, reads and

writes are inhibited. As VCC drops below the battery voltage, the RAM and

timekeeping circuits are switched over to the battery.

22 22 1 OE Output-Enable Input. Active-low input that enables DQ0–DQ7 for data output from

the device.

20 20 27 CE Chip-Enable Input. Active-low input to enable the device.

23 23 2 SQW

Square-Wave Output. When enabled, the SQW pin outputs a 32.768kHz square

wave. If the square wave (E32K) and battery backup 32kHz (BB32) bits are enabled,

power is provided by VBAUX when VCC is absent.

24 24 3 KS Active-Low Kickstart Input. This pin is used to wake up a system from an external

event, such as a key closure. The KS pin is normally connected using a pullup

resistor to VBAUX. If the KS function is not used, connect to ground.

25 — 4 VBAT Battery Input for Any Standard 3V Lithium Cell or Other Energy Source. Battery

voltage must be held between 2.5V and 3.7V for proper operation. UL recognized to

ensure against reverse charging current when used with a lithium battery.

www.maxim-ic.com/TechSupport/QA/ntrl.htm If not used, connect to ground.

26 26 5 VBAUX Auxiliary Battery Input for Any Standard 3V Lithium Cell or Other Energy Source.

Battery voltage must be held betw een 2.5V and 3.7V for proper operation. UL

recognized to ensure against reverse charging current when used with a lithium

battery. www.maxim-ic.com/TechSupport/QA/ntrl.htm If not used, connect to ground.

27 27 6 WE Write-Enable Input. Active-low input that enables DQ0–DQ7 for data input to the

device.

28 28 7 VCC DC Power. VCC is the positive terminal. When power is applied within the normal

limits, the device is fully accessible and data can be written and read. When VCC

drops below the normal limits, reads and writes are inhibited. As VCC drops below the

battery voltage, the RAM and timekeeping circuits are sw itched over to the battery.

— 2, 3, 21,

25 — N.C. No Connect

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

10 of 22

Figure 8. Block Diagram

256 x 8

NV SRAM

POWER CONTROL

WRITE PROTECTION,

AND POWER-ON

RESET

16 X 8

CLOCK AND CONTROL

REGISTERS

BAT

BAUX

GND

A0–A4

DQ0–DQ7

X2 32.768kHz CLOCK

OSCILLATOR

SQW

CLOCK ALARM AND WATCHDOG

COUNTDOWN

DS1501/DS1511

Figure 9. Typical Crystal Layout

CRYSTAL X1

GND

LOCAL GROUND PLANE (LAYER 2)

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

11 of 22

DETAILED DESCRIPTION

The DS1501/DS1511 RTC is a low-power clock/date device with a programmable day of week/date alarm. The

DS1501/DS1511 is accessed through a parallel interface. The clock/date provides seconds, minutes, hours, day,

date, month, and year information. The date at the end of the month is automatically adjusted for months with

fewer than 31 days, including co rrections for leap year.

The RTC registers are double buffered into an internal and external set. The user has direct access to the external

set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow the user to access

static data. When the crystal oscillator is turned on, the internal set of registers are continuously updated; this

occurs regardless of external regi ster settings to guarantee that accurate RTC information is always maintained.

The DS1501/DS1511 contain their own power-fail circuitry that automatically deselects the device when the VCC

supply falls below a power-fail trip point. This feature provides a high degree of data security during unpredictable

system operation caused by low VCC levels.

The DS1501/DS1511 have interrupt (IRQ), power control (PWR), and reset (RST) outputs that can be used to

control CPU activity. The IRQ interrupt or RST outputs can be invoked as the result of a time-of-day alarm, CPU

watchdog alarm, or a kickstart signal. The DS1501/DS1511 power-control circuitry allow the system to be powered

on by an external stimulus, such as a keyboard or by a time and date (wakeup) alarm. The PWR output pin can be

triggered by one or either of these events, and can be used to turn on an external power supply. The PWR pin is

under software control, so that when a task is complete, the system power can then be shut down. The

DS1501/DS1511 power-on reset can be used to detect a system power-down or failure and hold the CPU in a safe

reset state until normal power returns and stabilizes; the RST output is used for this function.

The DS1501/DS1511 are clock/calendar chips with the features described above. An external crystal and battery

are the only components required to maintain time-of-day and memory status in the absence of power.

Table 1. RTC Operating Modes

VCC CE OE WE DQ0–DQ7 A0–A4 MODE POWER

VIH X X High-Z X Deselect Standby

VIL X VIL D

IN A

IN Write Active

VIL V

IL V

IH D

OUT A

IN Read Active

In tolerance

VIL V

IH V

IH High-Z AIN Read Active

VSO < VCC < VPF X X X High-Z X Deselect CMOS Standby

VCC < VSO < VPF X X X High-Z X Data Retention Battery Current

DATA READ MODE

The DS1501/DS1511 are in read mode whenever CE (chip enable) and OE (output enable) are low and WE (wr ite

enable) is high. The device architecture allows ripple-through access to any valid address location. Valid data is

available at the DQ pins within tAA (address access) after the last address input is stable, provided that CE and OE

access times are satisfied. If CE or OE access times are not met, valid data is available at the latter of chip-enable

access (tCSA) or at output-enable access time (tOEA). The state of the data input/output pins (DQ) is controlled by CE

and OE. If the outputs are activated before tAA, the data lines are driven to an intermediate state until tAA. If the

address inputs are changed while CE and OE remain valid, output data remains valid for output-data hold time (tOH)

but then goes indeterminate until the next address access (Table 1).

DATA WRITE MODE

The DS1501/DS1511 are in write mo de whenever CE and WE are i n their active state. The start of a write is

referenced to the latter occurring transiti on of CE or WE. The addresses must be held valid throughout the cycle.

CE or WE must return inactive for a minimum of tWR prior to the initiation of a subsequent read or write cycle. Data

in must be valid tDS prior to the end of the write and remain valid for tDH afterward. In a typical application, the OE

signal is high during a write cycle. However, OE can be active provided that care is taken with the data bus to avoid

bus contention. If OE is low prior to a high-to-low transition on WE, the data bus can become active with read data

defined by the address inputs. A low transition on WE then disables the outputs tWEZ after WE goes active (Table 1).

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

12 of 22

DATA RETENTION MODE

The DS1501/DS1511 are fully accessible, and data can be written and read only when VCC is greater than VPF.

However, when VCC falls below the power-fail point VPF (point at which write protection occurs) the internal clock

registers and SRAM are blocked from any access. While in the data retention mode, all inputs are don’t cares and

outputs go to a high-Z state, with the possible exception of KS, PWR, SQW, and RST. If VPF is less than VBAT and

VBAUX, the device power is switched from VCC to the greater of VBAT and VBAUX when VCC drops below VPF. If VPF is

greater than VBAT and VBAUX, the device power is switched from VCC to the larger of VBAT and VBAUX when VCC drops

below the larger of VBAT and VBAUX. RTC operation and SRAM data are maintained from the battery until VCC is

returned to nominal levels (Table 1). If the square-wave and battery-backup 32kHz functions are enabled, VBAUX

always provides power for the square-wave output, when the device is in battery-backup mode .

AUXILIARY BATTERY

The VBAUX input is provided to supply power from an auxiliary battery for the DS1501/DS1511 kickstart and square-

wave output features in the absence of VCC. This power source must be available to use these auxiliary features

when VCC is not applied to the device.

This auxiliary battery can be used as the primary backup power source for maintaining the clock/calendar and

external user RAM. This occurs if the VBAT pin is at a lower voltage than VBAUX. If the DS1501/DS1511 are to be

backed up using a single battery with the auxiliary features enabled, then VBAUX should be used and VBAT should be

grounded (DS1501). If VBAUX is not to be used, it must be grounded.

OSCILLATOR CONTROL BIT

When the DS1511 is shipped from the factory, the internal oscillator is turned off. This feature prevents the lithium

energy cell from being used until it is installed in a system. The oscillator is automatically enabled when power is

first applied.

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 tREC. The power-on reset function is independent of the RTC oscillator and therefore operational

whether or not the oscillator is enabled.

TIME AND DATE OPERATION

The time and date information is obtained by reading the appropriate register bytes. Table 2 shows the RTC

registers. The time and date are set or initialized by writing the appropriate register bytes. The contents of the time

and date registers are in BCD format. Hours are in 24-hour mode. The day-of-week register increments at

midnight. Values that correspond to the day of week are user defined but must be sequential (i.e., if 1 equals

Sunday, then 2 equals Monday, and so on). Illogical time and date entries result in undefined operation.

READING THE CLOCK

When reading the clock and calendar data, it is possible to access the registers while an update (once per second)

occurs. There are three ways to avoid using invalid time and date data.

The first method uses the transfer enable (TE) bit in the control B register. Transfers are halted when a 0 is written

to the TE bit. Setting TE to 0 halts updates to the user-accessible registers, while allowing the internal registers to

advance. After the registers are read, the TE bit should be written to 1. TE must be kept at 1 for at least 366μs to

ensure a user register update.

The time and date registers can be read and stored in temporary variables. The time and date registers are then

read again, and compared to the first values. If the values do not match, the time and date registers should be read

a third time and compared to the previous values. This should be done until two consecutive reads of the time and

date registers match. The TE bit should always be enabled when using this method for reading the time and date,.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

13 of 22

The third method of reading the time and date uses the alarm function. The alarm can be configured to activate

once per second, and the time-of-day alarm-interrupt enable bit (TIE) is enabled. The TE bit should always be

enabled. When the IRQ pin goes active, the time and date information does not change until the next updat e.

SETTING THE C LO CK

It is recommended to halt updates to the external set of double-buffered RTC registers when writing to the clock.

The (TE) bit should be used as described above before loading the RTC registers with the desired RTC count (day,

date, and time) in 24-hour BCD format. Setting the TE bit to 1 transfers the new values written to the internal RTC

registers and allows normal operation to resume.

CLOCK ACCURACY

The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match between

the capacitive load of the oscillator circuit and the capacitive load for which the crystal was trimmed. Additional

error is added by crystal frequency drift caused by temperature shifts. External circuit noise coupled into the

oscillator circuit can result in the clock runnin g fast.

A standard 32.768kHz quartz crystal should be directly connected to the DS1501 X1 and X2 oscillator pins. The

crystal selected for use should have a specified load capacitance (CL) of either 6pF or 12.5pF, and the CS bit set

accordingly. An external 32.768kHz oscillator can also drive the DS1501. When using an external oscillator the X2

pin must be left open. The DS1511 contains an embedded crystal and is factory trimmed to be better than ±1

min/month at +25°C.

Refer to Application Note 58: Crystal Considerations for Dallas Real-Time Clocks for detailed information.

Table 2. Register Map

DATA

ADDRESS B7 B6 B5 B4 B3 B2 B1 B0 FUNCTION BCD

RANGE

00H 0 10 Seconds Seconds Seconds 00–59

01H 0 10 Minutes Minutes Minutes 00–59

02H 0 0 10 Hours Hour Hours 00–23

03H 0 0 0 0 0 Day Day 1–7

04H 0 0 10 Date Date Date 01–31

05H EOSC E32K BB32 10 Month Month Month 01–12

06H 10 Year Year Year 00–99

07H 10 Century Century Century 00–39

08H AM1 10 Seconds Seconds Alarm Seconds 00–59

09H AM2 10 Minutes Minutes Alarm Minutes 00–59

0AH AM3 0 10 Hours Hour Alarm Hours 00–23

0BH AM4 Dy/Dt 10 Date Day/Date Alarm Day/Date 1–7/1–31

0CH 0.1 Second 0.01 Second Watchdog 00–99

0DH 10 Second Second Watchdog 00–99

0EH BLF1 BLF2 PRS PAB TDF KSF WDF IRQF Control A

0FH TE CS BME TPE TIE KIE WDE WDS Control B

10H Extended RAM Address RAM Address 00–FF

11H Reserved

12H Reserved

13H Extended RAM Data RAM Data 00–FF

14H-1FH Reserved

Note: 0 = 0 and are read only.

POWER-UP DEFAULT STATES

These bits are set upon power-up: EOSC = 0, E32K = 0, TIE = 0, KIE = 0, WDE = 0, and WDS = 0. Unless

otherwise specified, the state of the control/RTC/SRAM bits in the DS1501/DS1511 is not defined upon initial

power application; the DS1501/DS1511 shoul d be properly configured/defined during initial configuration.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

14 of 22

USING THE CLOCK ALARM

The alarm settings and control reside within registers 08h to 0Bh (Table 2). The TIE bit and alarm mask bits AM1 to

AM4 must be set as described below for the IRQ or PWR outputs to be activated for a matched alarm condition.

The alarm functions as long as at least one supply is at a valid level. Note that activating the PWR pin requires the

use of VBAUX.

The alarm can be programmed to activate on a specific day of the month, day of the week, or repeat every day,

hour, minute, or second. It can also be programmed to go off while the DS1501/DS1511 are in the battery-backed

state of operation to serve as a system wakeup. Alarm mask bits AM1 to AM4 control the alarm mode. Table 3

shows the possible settings. Configurations not listed in the table default to the once-per-second mode to notify the

user of an incorrect alarm setting. When the RTC register values match alarm register settings, the time-of-

day/date alarm flag TDF bit is set to 1. Once the TDF flag is set, the TIE bit enables the alarm to activate the IRQ

pin. The TPE bit enables the alarm flag to activate the PWR pin. Note that TE must be enabled when a match

occurs for the flags to be set.

Table 3. Alarm Mask Bits

DY/DT AM4 AM3 AM2 AM1 ALARM RATE

X 1 1 1 1 Once per second

X 1 1 1 0 When seconds match

X 1 1 0 0 When minutes and seconds match

X 1 0 0 0 When hours, minutes, and seconds match

0 0 0 0 0 When date, hours, minutes, and seconds match

1 0 0 0 0 When day, hours, minutes, and seconds match

CONTROL REGISTERS

The DS1501/DS1511 co ntrols and status information for the features are maintained in the following register bits.

Month Register (05h)

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

EOSC E32K BB32 10 Month Month

EOSC, Oscillator Start/Stop Bit (05h Bit 7)

This bit when set to logic 0 starts the oscillator. When this bit is set to logic 1, the oscillator is stopped. This bit is

automatically set to logic 0 by the internal power-on reset when power is applied and VCC rises above the power-fail

voltage.

E32K, Enable 32.768kHz Outpu t (05h Bit 6)

This bit, when written to 0, enables the 32.768 kHz oscillator frequency to be output on the SQW pin if the oscillator

is running. This bit is automatically set to logic 0 by the internal power-on reset when power is applied and VCC

rises above the power-fail voltage.

BB32, Battery Backup 32kHz Enable Bit (05h Bit 5)

When the BB32 bit is written to 1, it enables a 32kHz signal to be output on the SQW pin while the part is in

battery-backup mode, if voltage is applied to VBAUX.

AM1 to AM4, Alarm Mask Bits (08H Bit 7; 09H Bit 7; 0AH Bit 7; 0BH Bit 7)

Bit 7 of registers 08h to 0Bh contains an alarm mask bit, AM1 to AM4. These bits, in conjunction with the TIE

described later, allow the IRQ output to be activated for a matched-alarm condition. The alarm can be programmed

to activate on a specific day of the month, day of the week, or repeat every day, hour, minute, or second. Table 3

shows the possible settings for AM1 to AM4 and the resulting alarm rates. Configurations not listed in the table

default to the once-per-second mode to notify the user of an incorrect alarm setting.

DY/DT, Day/Date Bit (0BH Bit 6 )

The DY/DT bit controls whether the alarm value stored in bits 0 to 5 of 0BH reflects the day of the week or the date

of the month. If DY/DT is written to a 0, the alarm is the result of a match with the date of the month. If DY/DT is

written to a 1, the alarm is the result of a match with the day of the week.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

15 of 22

Control A Register (0Eh)

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

BLF1 BLF2 PRS PAB TDF KSF WDF IRQF

BLF1, Valid RAM and Time Bit 1 (0Eh Bit 7); BLF2, Valid RAM and Time Bit 2 (0Eh Bit 6)

These status bits give the condition of any batteries attached to the VBAT or VBAUX pins. The DS1501/DS1511

constantly monitor the battery voltage of the backup-battery sources (VBAT and VBAUX). The BLF1 and BLF2 bits are

set to 1 if the battery voltages on VBAT and VBAUX are less than VBLF (typ), otherwise BLF1 and BLF2 bits are 0.

BLF1 reflects the condition of VBAT with BLF2 reflecting VBAUX. If either bit is read as 1, the voltage on the respective

pin is inadequate to maintain the RAM memory or clock functions. These bits are read only.

PRS, Reset Select Bit (0Eh Bit 5)

When set to 0, the PWR pin is set high-Z when the DS150/DS1511 go into power-fail. When set to 1, the PWR pin

remains active upon entering power-fail.

PAB, Power Active-Bar Control Bit (0Eh Bit 4)

When this bit is 0, the PWR pin is in the active-low state. When this bit is 1, the PWR pin is in the high-impedance

state. The user can write this bit to 1 or 0. If either TDF and TPE = 1 or KSF = 1, the PAB bit is cleared to 0. This bit

can be read or written.

TDF, Time-of-Day/Date Alarm Flag (0Eh Bit 3)

A 1 in the TDF bit indicates that the current time has matched the alarm time. If the TIE bit is also 1, the IRQ pin

goes low and a 1 appears in the IRQF bit. This bit is cleared by reading the register or writing i t to 0.

KSF, Kickstart Flag (0Eh Bit 2)

This bit is set to a 1 when a kickstart condition occurs or when the user writes it to 1. If the KIE bit is also 1, the IRQ

pin goes low and a 1 appears in the IRQF bit. This bit is cleared by reading the register or writing it to 0.

WDF, Watchdog Flag (0Eh Bit 1)

If the processor does not access the DS1501/DS1511 with a write within the period specified in addresses 0CH

and 0DH, the WDF bit is set to 1. WDF is cleare d by writing it to 0.

IRQF, Interrupt Request Flag (0Eh Bit 0)

The interrupt request flag (IRQF ) bit is se t to 1 when one or more of the following are true:

TDF = TIE = 1

KSF = KIE = 1

WDF = WDE = 1

i.e., IRQF = (TDF x TIE) + (KSF x KIE) + (WDF x WDE)

Any time the IRQF bit is 1, the IRQ pin is driven low.

Clearing IRQ and Flags

The time-of-day/date alarm flag (TDF), watchdog flag (WDF), kickstart flag (KSF), and interrupt request flag (IRQF)

are cleared by reading the flag register (0EH). The address must be stable for a minimum of 15ns while CE and OE

are active. After the address stable requirement has been met, either a change in address, a rising edge of OE, or

a rising edge of CE causes the flags to be cleared. The IRQ pin goes inactive after the IRQF flag is cleared. TDF

and WDF can also be cleared by writing to 0.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

16 of 22

Control B Register (0Fh)

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

TE CS BME TPE TIE KIE WDE WDS

TE, Transfer Enable Bit (0Fh Bit 7)

When the TE bit is 1, the update transfer functions normally by advancing the counts once per second. When the

TE bit is written to 0, any update transfer is inhibited and the program can initialize the time and calendar bytes

without an update occurring in the midst of initializing. Read cycles can be executed in a similar manner. TE is a

read/write bit that is not modified by internal functions of the DS150 1/DS1511.

CS, Crystal Select Bit (0 Fh Bit 6)

When CS is set to 0, the oscillator is configured for operation with a crystal that has a 6pF specified load

capacitance. When CS = 1, the oscillator is configured for a 12.5pF crystal. CS is disabled in the DS1511 module

and should be set to CS = 0.

BME, Burst-Mode Enable Bit (0 Fh Bit 5)

The burst-mode enable bit allows the extended user RAM address registers to automatically increment for

consecutive reads and writes. When BME is set to 1, the automatic incrementing is enabled; when BME is set to 0,

the automatic incrementing is disabled.

TPE, Time-of-Day/Date Alarm Power-Enable Bit (0Fh Bit 4)

The wakeup feature is controlled through the TPE bit. When the TDF flag bit is set to 1, if TPE is 1, the PWR pin is

driven active. Therefore, setting TPE to 1 enables the wakeup feature. Writing a 0 to TPE disables the wakeup

feature.

TIE, Time-of-Day/ Date Alarm Interrupt-Enable Bit (0Fh Bit 3)

The TIE bit allows the TDF flag to assert an interrupt. When the TDF flag bit is set to 1, if TIE is 1, the IRQF flag bit

is set to 1. Writing a 0 to the TIE bit prevents the TDF flag from setting the IRQF flag. This bit is automatically

cleared to logic 0 by the internal power-on reset when power is applied and VCC rises above the power-fail voltage.

KIE, Kickstart Enable-Interrupt Bit (0 Fh Bit 2)

The KIE bit allows the KSF flag to assert an interrupt. When the KSF flag bit is set to 1, if KIE is a 1, the IRQF flag

bit is set to 1. Writing a 0 to the KIE bit prevents the KSF flag from setting the IRQF flag. This bit is automatically

cleared to logic 0 by the internal power-on reset when power is applied and VCC rises above the power-fail voltage.

WDE, Watchdog Enable Bit (0Fh Bit 1)

When WDE is set to 1, the watchdog function is enabled, and either the IRQ or RST pin is pulled active, based on

the state of the WDS and WDF bits. This bit is automatically cleared to logic 0 to by the internal power-on reset

when power is applied and VCC rises above the power-fail voltage.

WDS, Watchdog Steering Bit (0Fh Bit 0)

If WDS is 0 when the watchdog flag bit WDF is set to 1, the IRQ pin is pulled low. If WDS is 1 when WDF is set to

1, the watchdog outputs a negative pulse on the RST output. The WDE bit resets to 0 immediately after RST goes

active. This bit is automatically cleared to logic 0 to by the internal power-on reset when power is applied and VCC

rises above the power-fail voltage.

CLOCK OSCILLATOR CONTROL

The clock oscillator can be stopped at any time. To increase the shelf life of a backup lithium-battery source, the

oscillator can be turned off to minimize current drain from the battery. The EOSC bit is used to control the state of

the oscillator, and must be set to 0 for the oscillator to function.

USING THE WATCHDOG TIMER

The watchdog timer can be used to restart an out-of-control processor. The watchdog timer is user programmable

in 10ms intervals ranging from 0.01 seconds to 99.99 seconds. The user programs the watchdog timer by writing

the timeout value into the two BCD watchdog registers (0Ch and 0Dh). The watchdog reloads and restarts

whenever the watchdog times out. Writing the timer will reoad and restart the timer. The timer runs while the device

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

17 of 22

is powered by either VCC, VBAT, or VBAUX. If either watchdog register is nonzero, a timeout sets the WDF bit to 1,

regardless of the state of the watchdog enable (WDE) bit, to serve as an indication to the processor that a

watchdog timeout has occurred. The watchdog timer operates in two modes, repetitive and single-shot.

If WDE is 1 and the watchdog steering bit (WDS) is 0, the watchdog is in repetitive mode. When the watchdog

times out, both WDF and IRQF are set. IRQ goes active and IRQF goes to 1. The watchdog timer is reloaded when

the processor performs a write of the watchdog registers and the timeout period restarts. Reading control A register

clears the IRQ flag.

If WDE and WDS are 1, the watchdog is in single-shot mode. When the watchdog times out, RST goes active for a

period of 40ms to 200ms. When RST goes inactive, WDE resets to 0. Writing a value of 00h to both watchdog

registers disables the watchdog timer. The watchdog function is automatically disabled upon power-up by the

power-on reset setting WDE = 0 and WDS = 0. The watchdog registers are not initialized at power-up and should

be initialized by the user.

Note: The TE bit must be used to disable transfers when writing to the watchdog registers.

The following summarizes the configurations in which the watchdog can be used:

WDE = 0 and WDS = 0: WDF is set.

WDE = 0 and WDS = 1: WDF is set.

WDE = 1 and WDS = 0: WDF and IRQF are set, and the IRQ pin is pulled low.

WDE = 1 and WDS = 1: WDF is set, the RST pin pulses low, and WDE resets to 0.

WAKEUP/KICKSTART

The DS1501/DS1511 incorporate a wakeup feature, which powers on at a predetermined day/date and time by

activating the PWR output pin. Additionally, the kickstart feature allows the system to be powered up in response to

a low-going transition on the KS pin, without operating voltage applied to the VCC pin. As a result, system power

can be applied upon such events as key closure or a modem-ring-detect signal. To use either the wakeup or the

kickstart features, the DS1501DS1511 must have an auxiliary battery connected to the VBAUX pin, and the oscillator

must be running.

The wakeup feature is controlled through the time-of-day/date power-enable bit (TPE). Setting TPE to 1 enables

the wakeup feature. Transfers (TE) must be enabled for a wake up event to occur. Writing TPE to 0 disables the

wakeup feature. The kickstart feature is always enabled as long as VBAUX is present.

If the wakeup feature is enabled, while the system is powered down (no VCC voltage), the clock/calendar monitors

the current day or date for a match condition with day/date alarm register (0Bh). With the day/date alarm register,

the hours, minutes, and seconds alarm bytes in the clock/calendar register map (02h, 01h, and 00h) are also

monitored. As a result, a wakeup occurs at the day or date and time specified by the day/date, hours, minutes, and

seconds alarm register values. This additional alarm occurs regardless of the programming of the TIE bit. When the

match condition occurs, the PWR pin is automatically driven low. This output can turn on the main system power

supply that provides VCC voltage to the DS1501/DS1511, as well as the other major components in the system.

Also at this time, the time-of-day/date alarm flag is set (TDF), indicating a wake up condition has occurred.

If VBAUX is present, while VCC is low, the KS input pin is monitored for a low-going transition of minimum pulse width

tKSPW. When such a transition is detected, the PWR line is pulled low, as it is for a wakeup condition. Also at this

time, KSF is set, indicating that a kickstart condition has occurred. The KS input pin is always enabled and must not

be allowed to float.

The timing associated with the wakeup and kickstarting sequences is illustrated in Figure 7. These functions are

divided into five intervals, labeled 1 to 5 on the diagram.

The occurrence of either a kickstart or wakeup condition causes the PWR pin to be driven low, as described above.

During Interval 1, if the supply voltage on the VCC pin rises above VSO before the power-on timeout period (tPOTO)

expires, then PWR remains at the active-low level. If VCC does not rise above the VSO in this time, then the PWR

output pin is turned off and returns to its high-impedance level. In this event, the IRQ pin also remains tri-stated.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

18 of 22

The interrupt flag bit (either TDF or KSF) associated with the attempted power-on sequence remains set until

cleared by software during a subsequent system power-o n.

If VCC is applied within the timeout period, the system power-on sequence continues, as shown in Intervals 2 to 5 in

the timing diagram. During Interval 2, PWR remains active, and IRQ is driven to its active-low level, indicating that

either TDF or KSF was set in initiating the power-on. In the diagram, KS is assumed to be pulled up to the VBAUX

supply. Also at this time, the PAB bit is automatically cleared to 0 in response to a succ essful power-on. The PWR

line remains active as long as the PAB remains cleared to 0.

At the beginning of Interval 3, the system processor has begun code execution and clears the interrupt condition of

TDF and/or KSF by reading the flags register or by writing TDF and KSF to 0. As long as no other interrupt within

the DS1501/DS1511 is pending, the IRQ line is taken inactive once these bits are reset, and execution of the

application software can proceed. During this time, the wakeup and kickstart functions can be used to generate

status and interrupts. TDF is set in response to a day/date, hours, minutes, and seconds match condition. KSF is

set in response to a low-going transition on KS. If the associated interrupt-enable bit is set (TDE and/or KIE), then

the IRQ line is driven low in response to enabled event. In addition, the other possible interrupt sources within the

DS1501/DS1511 can cause IRQ to be driven low. While system power is applied, the on-chip logic always attempts

to drive the PWR pin active in response to the enabled kickstart or wakeup condition. This is true even if PWR was

previously inactive as the result of power being applied by some means other than wakeup or kickstart.

The system can be powered down under software control by setting the PAB bit to 1. The PAB bit can only be set

to 1 after the TDF and KSF flags have been cleared to 0. Setting PAB to 1 causes the open-drain PWR pin to be

placed in a high-impedance state, as shown at the beginning of Interval 4 in the timing diagram. As VCC voltage

decays, the IRQ output pin is placed in a high-impedance state when VCC goes below VPF. If the system is to be

again powered on in response to a wakeup or kickstart, then both the TDF and KSF flags should be cleared, and

TPE and/or KIE should be enabled prior to setting the PAB bit.

During Interval 5, the system is fully powered down. Battery backup of the clock calendar and NV RAM is in effect

and IRQ is tri-stated, and monitoring of wakeup and kickstart takes place. If PRS = 1, PWR stays active; otherwise,

if PRS = 0, PWR is tri-stated.

SQUARE-WAVE OUTPUT

The square-wave output is enabled and disabled through the E32K bit. If the square wave is enabled (E32K = 0)

and the oscillator is running, then a 32.768kHz square wave is output on the SQW pin. If the battery-backup

32kHz-enable bit (BB32) is enabled, and voltage is applied to VBAUX, then the 32.768kHz square wave is output on

the SQW pin in the absence of VCC.

BATTERY MONITOR

The DS1501/DS1511 constantly monitor the battery voltage of the backup-battery sources (VBAT and VBAUX). The

battery low flags BLF1 and BLF2 are set to 1 if the battery voltages on VBAT and VBAUX are less than VBLF (typical);

otherwise, BLF1 and BLF2 are 0. BLF1 monitors VBAT and BLF2 monitors VBAUX.

256 x 8 EXTENDED RAM

Two on-chip latch registers control access to the SRAM. One register is used to hold the SRAM address; the other

is used to hold read/write data. The SRAM address space is from 00h to FFh. The 8-bit address of the RAM

location to be accessed must be loaded into the extended RAM address register located at 10h. Data in the

addressed location can be read by performing a read operation from location 13h, or written to by performing a

write operation to location 13h. Data in any addressed location can be read or written repeatedly with changing the

address in location 10h.

To read or write consecutive extended RAM locations, a burst mode feature can be enabled to increment the

extended RAM address. To enable the burst mode feature, set the BME bit to 1. With burst mode enabled, write

the extended RAM starting address location to register 10h. Then read or write the extended RAM data from/to

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

19 of 22

WE only when register 13h is being accessed (Figure 4). The address pointer wraps around after the last address

is accessed.

ORDERING INFORMATION (continued)

PART VOLTAGE (V) TEMP RANGE PIN-PACKAGE TOP MARK*

DS1501WN+ 3.3

-40C to +85C 28 DIP (0.600) DS1501WN

DS1501WZ+ 3.3

0C to +70C 28 SO (0.300) DS1501WZ

DS1501WZN+ 3.3

-40C to +85C 28 SO (0.300) DS1501WZN

DS1501WZN+T&R 3.3 -40C to +85C 28 SO (0.300)/Tape & Reel DS1501WZN

DS1501WZ+T&R 3.3

0C to +70C 28 SO (0.300)/Tape & Reel DS1501WZ

DS1501Y+ 5.0

0C to +70C 28 DIP (0.600) DS1501Y

DS1501YE+ 5.0

0C to +70C 28 TSOP DS1501YE

DS1501YEN+ 5.0

-40C to +85C 28 TSOP DS1501YEN

DS1501YEN+T&R 5.0

-40C to +85C 28 TSOP/Tape & Reel DS1501YEN

DS1501YE+T&R 5.0

0C to +70C 28 TSOP/Tape & Reel DS1501YE

DS1501YN+ 5.0

-40C to +85C 28 DIP (0.600) DS1501YN

DS1501YZ+ 5.0

0C to +70C 28 SO (0.300) DS1501YZ

DS1501YZN+ 5.0

-40C to +85C 28 SO (0.300) DS1501YZN

DS1501YZN+T&R 5.0

-40C to +85C 28 SO (0.300)/Tape & Reel DS1501YZN

DS1501YZ+T&R 5.0

0C to +70C 28 SO (0.300)/Tape & Reel DS1501YZ

DS1511W+ 3.3

0C to +70C 28 EDIP (0.720) DS1511W

DS1511Y+ 5.0

0C to +70C 28 EDIP (0.720) DS1511Y

+Denotes a lead(Pb)-free/RoHS-compliant package.

* A “+” anywhere on the top mark denotes a lead(Pb)-free package. An N or IND denotes an industrial temperature device.

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

20 of 22

PIN CONFIGURATIONS

EDIP

N.C.

DQ0

DQ1

DQ2

GND

SQW

N.C.

DQ7

DQ6

DQ5

DQ4

DQ3

VBAUX

N.C.

Maxim

DS1511

SQW

VBAUX

VBAT

VCC

GND

DQ6

DQ5

DQ4

DQ3

DQ2

DQ1

DQ0

GND

DQ7

TSOP

Maxim

DS1501

TOP VIEW

Maxim

DS1501

SQW

GND

DQ7

DQ6

DQ5

DQ4

DQ3

BAUX

BAT

DQ0

DQ1

DQ2

GND

DIP, SO

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

21 of 22

TYPICAL OPERATING CIRCUITS

DS1501

CPU

VCC

RST

GND

X2 X1

VCC

RPU CRYSTAL

SQW

VBAT

DQ0–DQ7

VBAUX

0–A4

IRQ

GND

DS1511

CPU

VCC

RST

GND

VCC

RPU

SQW

DQ0–DQ7

VBAU

0–A4

IRQ

GND

PACKAGE INFORMATION

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

PACKAGE TYPE DOCUMENT NUMBER

28-pin DIP (600 mils) 21-0044

28-pin SO (300 mils) 21-0042

28-pin TSOP (8mm x 13.4mm) 21-0273

28-pin EDIP (720 mils) 21-0241

DS1501/DS1511 Y2KC Watchdog Real-Time Clocks

22 of 22

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses

are implied. Maxim 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

REVISION HISTORY

REVISION

DATE DESCRIPTION PAGES

CHANGED

Removed the leaded parts from the Ordering Information table. 1, 19

Updated the Features section. 1

Removed the redundant operatin g temperature range line from the Absolute

Maximum Ratings section. 2

Moved the UL information link into the VBAT and VBAUX pin descriptions in the Pin

Description table. 9

080508

Added an overview to the Detailed Description section. 11

Replaced 330-mil SO package ord ering and top mark information with 300-mil

SO package information in the Ordering Information table. 1, 19

010909 Updated the Package Information table. 21