DS1685-3_12 MAXIM [Maxim Integrated Products], DS1685-3_12 Datasheet

Page 1

... Auxiliary Battery Input 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 ...

Page 2

... EDIP (0.740” EDIP (0.740” EDIP (0.740” EDIP (0.740” TOP MARK* DS1685-3 DS1685-5 DS1685-5 DS1685E-3 DS1685E DS1685E-3 DS1685E DS1685E-3 DS1685E DS1685E-3 DS1685E DS1685Q-3 DS1685Q-5 DS1685Q-3 DS1685Q-5 DS1685Q-3 DS1685Q-5 DS1685S-3 DS1685S-5 DS1685S-3 DS1685S-5 DS1687-3 ...

Page 3

... EDIP. The entire unit is fully tested at Maxim Integrated such that a minimum of 10 years of timekeeping and data retention in the absence guaranteed. CC 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 ...

Page 4

... No Connection. Pins missing by design. N.C. Connections for Standard 32.768kHz Quartz Crystal. For greatest accuracy, the DS1685 must be used with a crystal that has a specified load X1 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 ...

Page 5

... NAME Kickstart Input, Active Low. When V DS1685/DS1687, the system can be powered on in response to an active- low 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 KS start enable bit (KSE) must be set the kickstart function is used, and the KS pin must be pulled up to the V KS pin can be used as an interrupt input ...

Page 6

... AD0 - AD7 OSCILLATOR CIRCUIT The DS1685 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate. Table 1 specifies several crystal parameters for the external crystal, and Figure 2 shows a functional schematic of the oscillator circuit. The oscillator is controlled by an enable bit in the control register. ...

Page 7

... Refer to Application Note 58: Crystal Considerations with Dallas Real-Time Clocks for detailed information. The DS1685 can also be driven by an external 32.768 kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pin is floated. Refer to Application Note 58: Crystal Considerations with Dallas Real-Time Clocks for detailed information about crystal selection and crystal layout ...

Page 8

... A). This time period allows the system to stabilize after power is applied. If the oscillator is not enabled, the oscillator enable bit will be enabled on power up, and the device becomes immediately accessible. The DS1685/DS1687 is available in either device. The 5V device is fully accessible and data can be written and read only when V falls below V , read and writes are inhibited ...

Page 9

... Date 0 10 Month DV1 DV0 RS3 RS2 AIE UIE SQWE Century 10 Date DS1685/DS1687 3V/5V Real-Time Clocks BIT 1 BIT 0 FUNCTION Seconds Seconds Alarm Minutes Minutes Alarm Hours Hours Hours Hours Alarm Day Day Date Date Month Month Year ...

Page 10

... Year DV1 DV0 RS3 RS2 AIE UIE SQWE Century 10 Date DS1685/DS1687 3V/5V Real-Time Clocks BIT 1 BIT 0 FUNCTION Seconds Seconds Alarm Minutes Minutes Alarm Hours Hours Hours Hours Alarm Day Day Date Month Month Year RS1 RS0 ...

Page 11

CONTROL REGISTERS The four control registers and D reside in both bank 0 and bank 1. These registers are accessible at all times, even during the update cycle. Register A (0Ah) MSB BIT 7 BIT 6 UIP ...

Page 12

... When the AIE bit is set to 0, the AF bit does not initiate the IRQ signal. The internal functions of the DS1685/DS1687 do not affect the AIE bit. UIE – The update-ended interrupt-enable (UIE) bit is a read/write bit that enables the update-end flag (UF) bit in Register C to assert IRQ. The SET bit going high clears the UIE bit. SQWE – ...

Page 13

Register C (0Ch) MSB BIT 7 BIT 6 BIT 5 IQRF PF IRQF – The interrupt-request flag (IRQF) bit is set when one or more of the following are true PIE = ...

Page 14

... The IRQF bit in Register whenever the IRQ pin is being driven low as a result of one of the six possible active sources. Therefore, determination that the DS1685/DS1687 initiated an interrupt is accomplished by reading Register C and finding IRQF = 1. IRQF remains set until all enabled interrupt flag bits are cleared to 0 ...

Page 15

SQUARE-WAVE OUTPUT SELECTION The SQW pin can be programmed to output a variety of frequencies divided down from the 32.768kHz crystal tied to X1 and X2. The square-wave output is enabled and disabled by the SQWE bit in Register B ...

Page 16

Table 3. Periodic Interrupt Rate and Square-Wave Output Frequency EXT. SELECT BITS REGISTER A REG B E32K RS3 RS2 ...

Page 17

... PF EXTENDED FUNCTIONS The extended functions provided by the DS1685/DS1687 that are new to the RAMified RTC family are accessed by a software-controlled bank-switching scheme, as illustrated in Figure 5. In bank 0, the clock/calendar registers and 50 bytes of user RAM are in the same locations as for the DS1287 result, existing routines implemented within BIOS, DOS, or application software packages can gain access to the DS1685/DS1687 clock registers with no changes ...

Page 18

... Figure 5. DS1685/DS1687 Register Map and Extended Register Bank Definition BANK 0 DV0 MSB = 0 00 TIMEKEEPING AND CONTROL BYTES-USER RAM 3F 64 BYTES-USER RAM 7F When bank 1 is selected, the clock/calendar registers and the original 50 bytes of user RAM still appear as bank 0. However, the registers that provide control and status for the extended functions are accessed in place of the additional 64 bytes of user RAM ...

Page 19

... In the DS1685/DS1687, this auxiliary battery can be used as the primary backup-power source for maintaining the clock/calendar, user RAM, and extended external RAM functions. This occurs if the V than the DS1685 backed-up using a single battery with the auxiliary features enabled, then V BAUX should be used and V should be grounded ...

Page 20

... At the beginning of Interval 3, the system processor has begun code execution and clears the interrupt condition of WF and/ writing 0’s to both of these control bits. As long as no other interrupt within the DS1685/DS1687 is pending, the IRQ line is taken inactive once these bits are reset. Execution of the application software can proceed. ...

Page 21

... Two extended control registers are provided to supply controls and status information for the extended features offered by the DS1685/DS1687. These are designated as extended control registers 4A and 4B and are located in register bank 1, locations 04Ah and 04Bh, respectively. The functions of the bits within these registers are described as follows ...

Page 22

... RAM. When RCE = 0, RCLR and the RAM clear function are disabled. PRS – PAB Reset-Select Bit. When set the PWR pin is set high-Z when the DS1685 goes into power-fail. When set the PWR pin remains active upon entering power-fail. ...

Page 23

The RTC address is latched on the falling edge of the ALE signal. Each time an RTC address is latched, the register address stack is pushed. The stack is only four registers deep, holding the three previous RTC addresses in ...

Page 24

ABSOLUTE MAXIMUM RATINGS Voltage Range on Any Pin Relative to Ground………………………………………………………………….0.3V to +6V Operating Temperature Range, Commercial ...……………………………………………………………….0°C to +70°C Operating Temperature Range, Industrial…………………………………………………………………...-40°C to +85°C Storage Temperature Range EDIP………………………………....……………………………………………………………………….-40°C to +85°C PDIP, SO, TSSOP……………………………….…………………………………....………………….-55°C to +125°C Lead Temperature (soldering, ...

Page 25

DC ELECTRICAL CHARACTERISTICS (V = 5.0V±10 3.0V±10 PARAMETER (-5) Average V Power- CC Supply Current (-3) (-5) CMOS Standby Current ( 0.2V) (-3) CC Input Leakage Current (Any Input) Output Leakage ...

Page 26

RTC AC TIMING CHARACTERISTICS (V = 3.0V±10 0°C to +70° PARAMETER Cycle Time Pulse Width, RD/WR Low Pulse Width, RD/WR High Input Rise and Fall Time Chip-Select Setup Time Before Chip-Select Hold ...

Page 27

RTC AC TIMING CHARACTERISTICS (V = 5.0V±10 0°C to +70° ARAMETER Cycle Time Pulse Width, RD/WR Low Pulse Width, RD/WR High Input Rise and Fall Time Chip-Select Setup Time Before WR ...

Page 28

... DS1685/DS1667 BUS TIMING FOR READ CYCLE TO RTC AND RTC REGISTERS DS1685/DS1687 BUS TIMING FOR WRITE CYCLE TO RTC AND RTC REGISTERS ...

Page 29

POWER-UP/DOWN TIMING— +25°C) A PARAMETER CS High to Power-Fail Recovery at Power-Up V Slew Rate Power-Down CC V Slew Rate Power-Down CC V Slew Rate Power-Up CC Expected Data Retention POWER-UP/DOWN TIMING— +25°C) A PARAMETER CS ...

Page 30

POWER-UP CONDITION—3V CS 2.6V 2. POWER FAIL POWER-DOWN CONDITION— POWER FAIL REC 2. 2.7V 2.6V 2. ...

Page 31

POWER-UP CONDITION—5V CS 4.5V 4.25V 4. POWER FAIL POWER-DOWN CONDITION— POWER FAIL REC 4.5V FB 4.25V 4.0V 3. ...

Page 32

WAKE-UP/KICKSTART TIMING *THIS CONDITION CAN OCCUR WITH THE 3V DEVICE. NOTE: TIME INTERVALS SHOWN ABOVE ARE REFERENCED IN WAKE-UP/KICKSTART SECTION. Note 1: All voltages are referenced to ground. Note 2: Typical values are at +25°C and nominal supplies. Note 3: ...

Page 33

PACKAGE INFORMATION For the latest package outline information and land patterns www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing ...

Page 34

... Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance © 2012 Maxim Integrated Products, Inc. DS1685/DS1687 3V/5V Real-Time Clocks DESCRIPTION Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc ...