Datasheet DS 1687-5 Datasheet (FREI)

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AD0AD1AD2AD3A

IRQKSR



WR P

WRPWR

AD2AD3A

19-5215; Rev 4/10

www.maxim-ic.com

FEATURES

Incorporates Industry-Standard DS1287 PC Clock plus Enhanced Features Such as: Y2K Compliant

 +3V or +5V Operation  64-Bit Silicon Serial Number  Power-Control Circuitry Supports System

Power-On from Date/Time Alarm or Key Closure

 32kHz Output for Power Management  Crystal-Select Bit Allows RTC to Operate with

6pF or 12.5pF Crystal

 SMI Recovery Stack  242 Bytes Battery-Backed NV RAM  Auxiliary Battery Input

APPLICATIONS

Embedded Systems Utility Meters Security Systems Network Hubs, Bridges, and Routers

PIN CONFIGURATIONS

TOP VIEW

DS1685/DS1687

3V/5V Real-Time Clocks

 RAM Clear Input  Century Register  Date Alarm Register  Compatible with Existing BIOS for Original

DS1287 Functions

 Available as Chip (DS1685) or Stand-Alone

Encapsulated DIP (EDIP) with Embedded Battery and Crystal (DS1687)

 Timekeeping Algorithm Includes Leap-Year

Compensation Valid Through 2099

 Underwriters Laboratory (UL) Recognized

X1 X2

D0 D1 D2 D3

D4 D5 D6 D7

GND

1 2

DS1685/

DS1685S/ DS1685E

4 5 6 7 8 9 10 11 12

PDIP (0.600

SO (0.300)/

TSSOP (0.173)

24 23

22 21 20 19 18 17 16 15 14 13

SQW V

BAUX

CLR

BAT

GND

D0 D1

D4 D5 D6 D7

2 3 4 5 6 7 8

9 10 11 12

DS1687

D4 D5

N.C.

4 3 2 1 28 27 26

5 6

DS1685Q

7 8 9 10 11

12 13 14 15 16 17 18

AD6

N.C.

AD7

GND

VBAUX

SQW

CLR

BAT

23 22 21

GND

N.C.

ALE

N.C.

PLCC

GND

24 23

22 21 20 19 18 17 16 15 14 13

SQW V

BAUX

CLR

N.C.

EDIP (0.740)

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Page 2

DS1685/DS1687 3V/5V Real-Time Clocks

ORDERING INFORMATION

PART* TEMP RANGE

DS1685-3+ 0°C to +70°C 3 24 PDIP (0.600”) DS1685-3

DS1685-5+ 0°C to +70°C 5 24 PDIP (0.600”) DS1685-5 DS1685-5IND+ -40°C to +85°C 5 24 PDIP (0.600”) DS1685-5 DS1685E-3+ 0°C to +70°C 3 24 TSSOP (0.173”) DS1685E-3 DS1685E-5+ 0°C to +70°C 5 24 TSSOP (0.173”) DS1685E DS1685EN-3+ -40°C to +85°C 3 24 TSSOP (0.173”) DS1685E-3 DS1685EN-5+ -40°C to +85°C 5 24 TSSOP (0.173”) DS1685E DS1685E-3+T&R 0°C to +70°C 3 24 TSSOP (0.173”)/Tape & Reel DS1685E-3 DS1685E-5+T&R 0°C to +70°C 5 24 TSSOP (0.173”)/Tape & Reel DS1685E DS1685EN-3+T&R -40°C to +85°C 3 24 TSSOP (0.173”)/Tape & Reel DS1685E-3 DS1685EN-5+T&R -40°C to +85°C 5 24 TSSOP (0.173”) /T&R DS1685E DS1685Q-3+ 0°C to +70°C 3 28 PLCC DS1685Q-3 DS1685Q-5+ 0°C to +70°C 5 28 PLCC DS1685Q-5 DS1685QN-3+ -40°C to +85°C 3 28 PLCC DS1685Q-3 DS1685QN-5+ -40°C to +85°C 5 28 PLCC DS1685Q-5 DS1685Q-3+T&R 0°C to +70°C 3 28 PLCC/Tape & Reel DS1685Q-3 DS1685Q-5+T&R 0°C to +70°C 5 28 PLCC/Tape & Reel DS1685Q-5 DS1685S-3+ 0°C to +70°C 3 24 SO (0.300”) DS1685S-3 DS1685S-5+ 0°C to +70°C 5 24 SO (0.300”) DS1685S-5 DS1685S-3+T&R 0°C to +70°C 3 24 SO (0.300”)/Tape & Reel DS1685S-3 DS1685S-5+T&R 0°C to +70°C 5 24 SO (0.300”)/Tape & Reel DS1685S-5 DS1687-3+ 0°C to +70°C 3 24 EDIP (0.740”) DS1687-3 DS1687-5+ 0°C to +70°C 5 24 EDIP (0.740”) DS1687-5 DS1687-3IND+ -40°C to +85°C 3 24 EDIP (0.740”) DS1687-3 DS1687-5IND+ -40°C to +85°C 5 24 EDIP (0.740”) DS1687-5

VOLTAGE

(V)

PIN-PACKAGE TOP MARK*

+Denotes a lead(Pb)-free/RoHS-compliant device. A “+” anywhere on the top mark indicates a lead-free/RoHS-compliant device.

*An “N” or “IND” denotes an industrial temperature grade device.

TYPICAL OPERATING CIRCUIT

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DS1685/DS1687 3V/5V Real-Time Clocks

DETAILED DESCRIPTION

The DS1685/DS1687 are real-time clocks (RTC) designed as successors to the industry-standard DS1285, DS1385, DS1485, and DS1585 PC RTCs. These devices provide the industry-standard DS1285 clock function with either +3.0V or +5.0V operation. The DS1685 also incorporates a number of enhanced features including a silicon serial number, power-on/off control circuitry, 242 bytes of user NV SRAM, and 32.768kHz output for sustaining power management activities.

The DS1685/DS1687 power-control circuitry allows the system to be powered on by an external stimulus such as a keyboard or by a time and date (wake-up) 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 DS1685 is a clock/calendar chip 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. The DS1687 incorporates the DS1685 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-contained timekeeping EDIP. The entire unit is fully tested at Maxim such that a minimum of 10 years of timekeeping and data retention in the absence of V

is guaranteed.

OPERATION

The block diagram in Figure 1 shows the pin connections with the major internal functions of the DS1685/DS1687. The following paragraphs describe the function of each pin.

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PIN DESCRIPTIONS

DS1685 DS1687

PDIP,

SO,

TSSOP

1 2 1

—

2 3 — X1

3 4 — X2

4–11

12, 16 15, 20 12 GND

PLCC EDIP

1, 11, 13,

5–10, 12,

2, 3, 16,

4–11 AD0–AD7

NAME FUNCTION

PWR

N.C.

DS1685/DS1687 3V/5V Real-Time Clocks

Active Low Power-On Output, Open Drain. The PWR pin is intended for use as an on/off control for the system power. With V the DS1685/DS1687, PWR can be automatically activated from a kickstart input by the KS pin or from a wake-up interrupt. Once the system is powered on, the state of PWR can be controlled by bits in the Maxim registers. The PWR pin can be connected through a pullup resistor to a positive supply. The voltage of the pullup supply should be no greater than

5.5V. No Connection. Pins missing by design.

Connections for Standard 32.768kHz Quartz Crystal. For greatest accuracy, the DS1685 must be used with a crystal that has a specified load capacitance of either 6pF or 12.5pF. The crystal-select (CS) bit in Extended Control Register 4B 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. Note: X1 and X2 are very highimpedance nodes. It is recommended that they and the crystal be guardringed with ground and that high-frequency signals be kept away from the crystal area.

Multiplexed, Bidirectional Address/Data Bus. The addresses are present during the first portion of the bus cycle and the same pins and signal paths are used for data in the second portion of the cycle. Address/data multiplexing does not slow the access time of the DS1685 since the bus change from address to data occurs during the internal RAM access time. Addresses must be valid prior to the latter portion of ALE, at which time the DS1685/DS1687 latches the address. Valid write data must be present and held stable during the latter portion of the WR pulse. In a read cycle, the DS1685/DS1687 outputs 8 bits of data during the latter portion of the RD pulse. The read cycle is terminated and the bus returns to a highimpedance state as RD transitions high. The address/data bus also serves as a bidirectional data path for the extended RAM.

Ground

voltage removed from

Chip-Select Input, Active-Low. The chip-select signal must be asserted low during a bus cycle for the RTC portion of the DS1685/DS1687 to be

13 16 13

14 17 14 ALE

15 19 15

17 21 17

accessed. CS must be kept in the active state during RD and WR timing. Bus cycles that take place with ALE asserted but without asserting CS will latch addresses. However, no data transfer will occur.

Address-Strobe Input, Active High. A pulse on the address strobe pin serves to demultiplex the bus. The falling edge of ALE causes the RTC address to be latched within the DS1685/DS1687.

Write Input, Active Low. The WR signal is an active-low signal. The WR signal defines the time period during which data is written to the addressed register.

Read Input, Active Low. RD identifies the time period when the DS1685/DS1687 drives the bus with RTC read data. The RD signal is an enable signal for the output buffers of the clock.

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Page 5

PIN DESCRIPTIONS (continued)

DS1685/DS1687 3V/5V Real-Time Clocks

DS1685 DS1687

PDIP,

SO,

PLCC EDIP

TSSOP

18 22 18

19 23 19

20 24 — V

21 25 21

NAME

IRQ

BAT

RCLR

FUNCTION

Kickstart Input, Active Low. When V

is removed from the

DS1685/DS1687, the system can be powered on in response to an activelow transition on the KS pin, as might be generated from a key closure. V

must be present and the auxiliary-battery enable bit (ABE) and kick-

BAUX

start enable bit (KSE) must be set to 1 if the kickstart function is used, and the KS pin must be pulled up to the V

supply. While VCC is applied, the

BAUX

KS pin can be used as an interrupt input. If not used, connect to V V

BAUX

if V

BAUX

is used.

Interrupt-Request Output, Open Drain, Active Low. The IRQ pin is an active-low output of the DS1685/DS1687 that can be connected to the interrupt input of a processor. The IRQ output remains low as long as the status bit causing the interrupt is present and the corresponding interruptenable bit is set. To clear the IRQ pin, the application software must clear all the enabled flag bits contributing to IRQ’s active state asserted but without asserting CS latch addresses. However, no data transfer occurs.

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. V

must be grounded if not used. Diodes should not be placed between

BAT

and the battery. See “Conditions of Acceptability” at

BAT

www.maxim-ic.com/UL

RAM Clear Input, Active Low. If enabled by software, taking RCLR low clears the 242 bytes of user RAM to FFh. When enabled, RCLR can be activated whether or not V

is present. The RCLR function is designed to

be used by a human interface (shorting to ground manually or by a switch) and not to be driven with external buffers. This pin is internally pulled up. Do not use an external pullup resistor on this pin.

, or to

Auxiliary Battery Input. Required for kickstart and wake-up features. This input also supports clock/ calendar and user RAM if V or is not present. A standard +3V lithium cell or other energy source can be

22 26 22 V

BAUX

used. Battery voltage must be held between +2.5V and +3.7V for proper operation. If V Auxiliary-Battery Enable bit bank 1, register 4BH, should be written to 0. See “Conditions of Acceptability” at www.maxim-ic.com/UL

Square-Wave Output. The SQW pin provides a 32kHz square-wave output, t

REC

following bits, enabling the 32kHz output; DV1 = 1, and E32K = 1. A square wave is output on this pin if either SQWE = 1 or E32K = 1. If E32K = 1, then 32kHz is output regardless of the other control bits. If E32K = 0, then the output frequency is dependent on the control bits in register A. The SQW

23 27 23 SQW

pin can output a signal from one of 13 taps provided by the 15 internal divider stages of the RTC. The frequency of the SQW pin can be changed by programming Register A as shown in Table 3. The SQW signal can be turned on and off using the SQWE bit in register B or the E32K bit in extended register 4Bh. A 32kHz SQW signal is output when the enable32kHz (E32K) bit in extended register 4Bh is a logic 1 and V V

. A 32kHz square wave is also available when VCC is less than VPF if

E32K = 1, ABE = 1, and voltage is applied to the V DC Power for Primary Power Supply. When V

24 28 24 VCC

normal limits, the device sis fully accessible and data can be written and read. When VCC is below VPF reads and writes are inhibited.

is at lower voltage

BAT

is not going to be used it should be grounded, and

BAUX

, after a power-up condition has been detected. This condition sets the

is above

pin.

BAUX

is applied within the

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