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MK41T56 MKI41T56
512 bit (64b x8) Serial Access TIMEKEEPER(R) SRAM
COUNTERS for SECONDS, MINUTES, HOURS, DAY, DATE, MONTH and YEARS SOFTWARE CLOCK CALIBRATION AUTOMATIC POWER-FAIL DETECT and SWITCH CIRCUITRY I2C BUS COMPATIBLE 56 BYTES of GENERAL PURPOSE RAM ULTRA-LOW BATTERY SUPPLY CURRENT of 500nA OPERATING TEMPERATURE: - MK41T56: 0 to 70C - MKI41T56: -40 to 85C AUTOMATIC LEAP YEAR COMPENSATION DESCRIPTION The MK41T56 TIMEKEEPER(R) is a low power 512 bit static CMOS RAM organized as 64 words by 8 bits. A built-in 32.768 kHz oscillator (external crystal controlled) and the first 8 bytes of the RAM are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. Addresses and data are transferred serially via a two-line bi-directional bus. The built-in address register is incremented automatically after each write or read data byte. The MK41T56 clock has a built-in power sense circuit which detects power failures and automatically switches to the battery supply during power failures. The energy needed to sustain the RAM and clock operations can be supplied from a small lithium button cell. Table 1. Signal Names
OSCI OCSO FT/OUT SDA SCL VBAT VCC VSS March 1999 Oscillator Input Oscillator Output Frequency Test / Output Driver (Open Drain) Serial Data Address Input / Output Serial Clock Battery Supply Voltage Supply Voltage Ground 1/15
8 1
PSDIP8 (N) 0.4mm Frame
8 1
SO8 (S) 150mil Width
Figure 1. Logic Diagram
VCC
VBAT
OSCI SCL MK41T56 MKI41T56
OSCO SDA FT/OUT
VSS
AI02304
MK41T56, MKI41T56
Figure 2A. DIP Pin Connections Figure 2B. SOIC Pin Connections
MK41T56 MKI41T56 OSCI OSCO VBAT VSS 1 2 3 4 8 7 6 5
AI02305
MK41T56 MKI41T56
VCC FT/OUT SCL SDA
OSCI OSCO VBAT VSS
1 2 3 4
8 7 6 5
AI02306
VCC FT/OUT SCL SDA
Table 2. Absolute Maximum Ratings
Symbol TA TSTG VIO VCC IO PD Parameter Ambient Operating Temperature MK41T56 MKI41T56 Value 0 to 70 -40 to 85 -55 to 125 -0.3 to 7 -0.3 to 7 20 0.25 Unit C C V V mA W
Storage Temperature (VCC Off, Oscillator Off) Input or Output Voltages Supply Voltage Output Current Power Dissipation
Note: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to the absolute maximum rating conditions for extended periods of time may affect reliability. CAUTION: Negative undershoots below -0.3 volts are not allowed on any pin while in the Battery Back-up mode.
Table 3. Register Map
Address D7 0 1 2 3 4 5 6 7 OUT ST X X X X X X X X X D6 D5 10 Seconds 10 Minutes 10 Hours X X X Date Month Years Calibration D4 Data D3 D2 D1 D0 Function/Range BCD Format Seconds Minutes Hour Day Date Month Year Control 00-59 00-59 00-23 01-07 01-31 01-12 00-99
Seconds Minutes Hours Day
10 Date X 10 M.
10 Years FT S
Keys: S = SIGN Bit; FT = FREQUENCY TEST Bit; ST = STOP Bit; OUT = Output level; X = Don't care.
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MK41T56, MKI41T56
Figure 3. Block Diagram
1 Hz OSCI OSCILLATOR 32.768 kHz OSCO FT/OUT VCC VSS VBAT VOLTAGE SENSE and SWITCH CIRCUITRY DIVIDER SECONDS MINUTES HOURS DAY DATE MONTH CONTROL LOGIC YEAR CONTROL
SCL
SERIAL BUS INTERFACE
RAM (56 x 8) ADDRESS REGISTER
SDA
AI00586C
DESCRIPTION (cont'd) Data retention time is in excess of 10 years with a 50mAh 3V lithium cell. The MK41T56 is supplied in 8 pin Plastic Dual-in-Line and 8 lead Plastic SOIC packages. OPERATION The MK41T56 clock operates as a slave device on the serial bus. Access is obtained by implementing a start condition followed by the correct slave address (11010000). The 64 bytes contained in the device can then be accessed sequentially in the following order: 1. Seconds Register 2. Minutes Register 3. Hours Register 4. Day Register 5. Date Register 6. Month Register 7. Years Register 8. Control Register 9 to 64. RAM
Table 4. AC Measurement Conditions
Input Rise and Fall Times Input Pulse Voltages Input and Output Timing Ref. Voltages 5ns 0 to 3V 1.5V
Note that Output Hi-Z is defined as the point where data is no longer driven.
Figure 4. AC Testing Load Circuit
5V
1.8k DEVICE UNDER TEST 1k
OUT
CL = 100pF
CL includes JIG capacitance
AI01019
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MK41T56, MKI41T56
Table 5. Capacitance (1,2) (TA = 25 C, f = 1 MHz )
Symbol CIN COUT
(2)
Parameter Input Capacitance (SCL) Output Capacitance (SDA, FT/OUT)
Min
Max 7 10
Unit pF pF
Notes: 1. Effective capacitance measured with power supply at 5V. 2. Sampled, not 100% tested. 3. Outputs deselected.
Table 6. DC Characteristics (TA = 0 to 70C or -40 to 85C; VCC = 4.5V to 5.5V)
Symbol ILI ILO ICC1 ICC2 VIL VIH VOL VBAT
(1)
Parameter Input Leakage Current Output Leakage Current Supply Current Supply Current (Standby) Input Low Voltage Input High Voltage Output Low Voltage Battery Supply Voltage Battery Supply Current
Test Condition 0V VIN VCC 0V VOUT VCC SCL/SDA = VCC-0.3V
Min
Typ
Max 10 10 1 1
Unit A A mA mA V V V V nA
-0.3 3 IOL = 5mA, VCC = 4.5V 2.6 TA = 25C, VCC = 0V, Oscillator ON, VBAT = 3V 3 450
1.5 VCC + 0.8 0.4 3.5 500
IBAT
Note: 1. The RAYOVAC BR1225 or equivalent is recommended as the battery supply.
Table 7. Power Down/Up Trip Points DC Characteristics (1) (TA = 0 to 70C or -40 to 85C)
Symbol VPFD VSO Parameter Power-fail Deselect Voltage Battery Back-up Switchover Voltage Min 1.2 VBAT Typ 1.25 VBAT VBAT Max 1.285 VBAT Unit V V
Note: 1. All voltages referenced to VSS.
Table 8. Crystal Electrical Characteristics (Externally Supplied)
Symbol fO RS CL
Notes:
Parameter Resonant Frequency Series Resistance Load Capacitance
Min
Typ 32.768
Max
Unit kHz
35 12.5
k pF
Load capacitors are integrated within the MK41T56. Circuit board layout considerations for the 32.768 kHz crystal of minimum trace lengths and isolation from RF generating signals should be taken into account.
STMicroelectronics recommends the ECS-.327-12.5-8SP-2 quartz crystal is recommended for industrial temperature operations. ESC Inc. can be contacted at 800-237-1041 or 913-782-7787 for further information on this crystal type.
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MK41T56, MKI41T56
Table 9. Power Down/Up Mode AC Characteristics (TA = 0 to 70C or -40 to 85C)
Symbol tPD tFB tRB tREC Parameter SCL and SDA at VIH before Power Down VPFD (min) to VSO VCC Fall Time VSO to VPFD (min) VCC Rise Time SCL and SDA at VIH after Power Up Min 0 300 100 200 Max Unit ns s s s
Figure 5. Power Down/Up Mode AC Waveforms
VCC VPFD VSO tPD SDA SCL tFB tRB tREC
IBAT DATA RETENTION TIME
AI00595
OPERATION (cont'd) The clock continually monitors VCC for an out of tolerance condition. Should VCC fall below VPFD, the device terminates an access in progress and resets the device address counter. Inputs to the device will not be recognized at this time to prevent erroneous data from being written to the device from an out of tolerance system. When VCC falls below VBAT, the device automatically switches over to the battery and powers down into an ultra low current mode of operation to conserve battery life. Upon power-up, the device switches from battery to VCC at VBAT and recognizes inputs when VCC goes above VPFD volts.
2-WIRE BUS CHARACTERISTICS This bus is intended for communication between different ICs. It consists of two lines: one bi-directional for data signals (SDA) and one for clock signals (SCL). Both the SDA and the SCL lines must be connected to a positive supply voltage via a pull-up resistor. The following protocol has been defined: - Data transfer may be initiated only when the bus is not busy. - During data transfer, the data line must remain stable whenever the clock line is High. - Changes in the data line while the clock line is High will be interpreted as control signals.
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MK41T56, MKI41T56
Table 10. AC Characteristics (TA = 0 to 70C or -40 to 85C; VCC = 4.5V to 5.5V)
Symbol fSCL tLOW tHIGH tR tF tHD:STA tSU:STA tSU:DAT (1) tHD:DAT tSU:STO tBUF tI SCL Clock Frequency Clock Low Period Clock High Period SDA and SCL Rise Time SDA and SCL Fall Time START Condition Hold Time (after this period the first clock pulse is generated) START Condition Setup Time (only relevant for a repeated start condition) Data Setup Time Data Hold Time STOP Condition Setup Time Time the bus must be free before a new transmission can start Noise suppression time constant at SCL and SDA input 4 4.7 250 0 4.7 4.7 0.25 1 Parameter Min 0 4.7 4 1 300 Max 100 Unit kHz s s s ns s s ns s s s s
Note: 1. Transmitter must internally provide a hold time to bridge the undefined region (300ns max.) of the falling edge of SCL.
2-WIRE BUS CHARACTERISTICS (cont'd) Accordingly, the following bus conditions have been defined: Bus not busy. Both data and clock lines remain High. Start data transfer. A change in the state of the data line, from High to Low, while the clock is High, defines the START condition. Stop data transfer. A change in the state of the data line, from Low to High, while the clock is High, defines the STOP condition. Data valid. The state of the data line represents valid data when after a start condition, the data line is stable for the duration of the High period of the clock signal. The data on the line may be changed during the Low period of the clock signal. There is one clock pulse per bit of data. Each data transfer is initiated with a start condition and terminated with a stop condition. The number of data bytes transferred between the start and stop conditions is not limited. The information is transmitted byte-wide and each receiver acknowledges with a ninth bit. By definition, a device that gives out a message is called "transmitter", the receiving device that gets
the message is called "receiver". The device that controls the message is called "master". The devices that are controlled by the master are called "slaves". Acknowledge. Each byte of eight bits is followed by one acknowledge bit. This acknowledge bit is a low level put on the bus by the receiver, whereas the master generates an extra acknowledge related clock pulse. A slave receiver which is addressed is obliged to generate an acknowledge after the reception of each byte. Also, a master receiver must generate an acknowledge after the reception of each byte that has been clocked out of the slave transmitter. The device that acknowledges has to pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is a stable Low during the High period of the acknowledge related clock pulse. Of course, setup and hold times must be taken into account. A master receiver must signal an end-of-data to the slave transmitter by not generating an acknowledge on the last byte that has been clocked out of the slave. In this case, the transmitter must leave the data line High to enable the master to generate the STOP condition.
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MK41T56, MKI41T56
Figure 6. Serial Bus Data Transfer Sequence
DATA LINE STABLE DATA VALID
CLOCK
DATA
START CONDITION
CHANGE OF DATA ALLOWED
STOP CONDITION
AI00587
Figure 7. Acknowledgement Sequence
CLOCK PULSE FOR ACKNOWLEDGEMENT 1 2 8 9
START SCLK FROM MASTER
DATA OUTPUT BY TRANSMITTER
DATA 1
DATA 2
DATA 8
DATA OUTPUT BY RECEIVER
AI00588
Figure 8. Bus Timing Requirements Sequence
SDA tBUF tHD:STA tR SCL tHIGH P S tLOW tSU:DAT tHD:DAT tSU:STA SR P tSU:STO tF tHD:STA
AI00589
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MK41T56, MKI41T56
WRITE MODE In this mode the master transmitter transmits to the MK41T56 slave receiver. Bus protocol is shown in Figure 10. Following the START condition and slave address, a logic '0' (R/W = 0) is placed on the bus and indicates to the addressed device that word address An will follow and is to be written to the on-chip address pointer. The data word to be written to the memory is strobed in next and the internal address pointer is incremented to the next memory location within the RAM on the reception of an acknowledge clock. The MK41T56 slave receiver will send an acknowledge clock to the master transmitter after it has received the slave address and again after it has received the word address and each data byte (see Figure 9). READ MODE In this mode, the master reads the MK41T56 slave after setting the slave address (see Figure 11). Following the write mode control bit (R/W = 0) and the acknowledge bit, the word address An is written to the on-chip address pointer. Next the START condition and slave address are repeated, followed by the READ mode control bit (R/W = 1). At this point, the master transmitter becomes the master receiver. The data byte which was addressed will be transmitted and the master receiver will send an acknowledge bit to the slave transmitter. The address pointer is only incremented on reception of an acknowledge bit. The MK41T56 slave transmitter will now place the data byte at address An + 1 on the bus. The master receiver reads and acknowledges the new byte and the address pointer is incremented to An + 2. This cycle of reading consecutive addresses will continue until the master receiver sends a STOP condition to the slave transmitter. An alternate READ mode may also be implemented, whereby the master reads the MK41T56 slave without first writing to the (volatile) address pointer. The first address that is read is the last one stored in the pointer, see Figure 12. CLOCK CALIBRATION The MK41T56 is driven by a quartz controlled oscillator with a nominal frequency of 32,768 Hz. A typical MK41T56 is accurate within 1 minute per month at 25C without calibration. The devices are tested not to exceed 35 ppm (parts per million) oscillator frequency error at 25C, which equates to about 1.53 minutes per month. The oscillation rate of any crystal changes with temperature (see Figure 14). Most clock chips compensate for crystal frequency and temperature shift error with cumbersome trim capacitors. The MK41T56 design, however, employs periodic counter correction. The calibration circuit adds or subtracts counts from the oscillator divider circuit at the divide by 256 stage, as shown in Figure 13. The number of times pulses are blanked (subtracted, negative calibration) or split (added, positive calibration) depends upon the value loaded into the five bit Calibration byte found in the Control Register. Adding counts speeds the clock up, subtracting counts slows the clock down. The Calibration byte occupies the five lower order bits in the Control register. This byte can be set to represent any value between 0 and 31 in binary form. The sixth bit is a sign bit; '1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs within a 64 minute cycle. The first 62 minutes in the cycle may, once per minute, have one second either shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is loaded into the register, only the first 2 minutes in the 64 minutes cycle will be modified; if a binary 6 is loaded, the first 12 will be affected, and so on.
Figure 9. Slave Address Location
R/W
START
SLAVE ADDRESS
A
1
1
0
1
0
0
0
AI00590
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MK41T56, MKI41T56
Figure 10. Write Mode Sequence
START
BUS ACTIVITY: MASTER SDA LINE
S
WORD ADDRESS (n)
DATA n
DATA n+1
DATA n+X
P
ACK
ACK
ACK
ACK
BUS ACTIVITY: SLAVE ADDRESS
AI00591
Figure 11. Read Mode Sequence
START START R/W
BUS ACTIVITY: MASTER SDA LINE
S
WORD ADDRESS (n)
S
R/W
DATA n
DATA n+1
ACK
ACK
ACK
ACK
BUS ACTIVITY: SLAVE ADDRESS
SLAVE ADDRESS
DATA n+X
P
NO ACK
STOP
AI00592B
Figure 12. Alternate Read Mode Sequence
START
BUS ACTIVITY: MASTER SDA LINE
S
DATA n
DATA n+1
DATA n+X
P
ACK
ACK
ACK
ACK
BUS ACTIVITY: SLAVE ADDRESS
AI00593
ACK
STOP
R/W
ACK
ACK
STOP
R/W
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MK41T56, MKI41T56
Figure 13. Clock Calibration
NORMAL
POSITIVE CALIBRATION
NEGATIVE CALIBRATION
AI00594B
CLOCK CALIBRATION (cont'd) Therefore, each calibration step has the effect of adding 512 or subtracting 256 oscillator cycles for every 125,829,120 actual oscillator cycles, that is + 4.068 or -2.034 ppm of adjustment per calibration step in the calibration register. Assuming that the oscillator is in fact running at exactly 32,768 Hz, each of the 31 increments in the Calibration byte would represent 10.7 seconds per month. Two methods are available for ascertaining how much calibration a given MK41T56 may require. The first involves simply setting the clock, letting it run for a month and comparing it to a known accurate reference (like WWV broadcasts). While that may seem crude, it allows the designer to give the end user the ability to calibrate his clock as his environment may require, even after the final product is packaged in a non-user serviceable enclosure. All the designer has to do is provide a simple utility that accessed the Calibration byte. The second approach is better suited to a manufacturing environment, and involves the use of
some test equipment. When the Frequency Test (FT) bit, the seventh-most significant bit in the Control Register, is set to a '1', and the oscillator is running at 32,768 Hz, the FT/OUT pin of the device will toggle at 512 Hz. Any deviation from 512 Hz indicates the degree and direction of oscillator frequency shift at the test temperature. For example, a reading of 512.01024 Hz would indicate a +20 ppm oscillator frequency error, requiring a -10(XX001010) to be loaded into the Calibration Byte for correction. Note that setting or changing the Calibration Byte does not affect the Frequency test output frequency. OUTPUT DRIVER PIN When the FT bit is not set, the FT/OUT pin becomes an output driver that reflects the contents of D7 of the control register. In other words, when D6 of location 7 is a zero and D7 of location 7 is a zero and then the FT/OUT pin will be driven low. Note: The FT/OUT pin is open drain which requires an external pull-up resistor.
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MK41T56, MKI41T56
Figure 14. Crystal Accuracy Across Temperature
ppm 20
0
-20
-40 F = -0.038 ppm (T - T )2 10% 0 F C2 T0 = 25 C -80
-60
-100 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 C
AI02124
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MK41T56, MKI41T56
ORDERING INFORMATION SCHEME
Example:
MKI41T56
N
00
TR
Operating Temp. blank I 0 to 70C -40 to 85C S N
Package PSDIP8 0.4mm Frame SO8 0.15mm Frame 00
Speed No Speed Options
Shipping Method for SO blank TR Tubes Tape & Reel
For a list of available options or for further information or any aspect of this device, please contact the STMicroelectronics Sales Office nearest to you.
12/15
MK41T56, MKI41T56
PSDIP8 - 8 pin Plastic Skinny DIP, 0.4mm lead frame
Symb Typ A A1 A2 B B1 C D E E1 e1 eA eB L N 3.00 8 2.54 7.62 0.70 3.10 0.38 1.15 0.38 9.20 - 6.30 - 8.40 mm Min Max 4.80 - 3.60 0.58 1.65 0.52 9.90 - 7.10 - - 9.20 3.80 0.118 8 0.100 0.300 0.028 0.122 0.015 0.045 0.015 0.362 - 0.248 - 0.331 Typ inches Min Max 0.189 - 0.142 0.023 0.065 0.020 0.390 - 0.280 - - 0.362 0.150
A2 A1 B B1 D
N
A L eA eB C
e1
E1
1
E
PSDIP-a
Drawing is not to scale.
13/15
MK41T56, MKI41T56
SO8 - 8 lead Plastic Small Outline, 150 mils body width
Symb Typ A A1 B C D E e H h L N CP 1.27 mm Min 1.35 0.10 0.33 0.19 4.80 3.80 - 5.80 0.25 0.40 0 8 0.10 Max 1.75 0.25 0.51 0.25 5.00 4.00 - 6.20 0.50 0.90 8 0.050 Typ inches Min 0.053 0.004 0.013 0.007 0.189 0.150 - 0.228 0.010 0.016 0 8 0.004 Max 0.069 0.010 0.020 0.010 0.197 0.157 - 0.244 0.020 0.035 8
h x 45 A C B e D CP
N
E
1
H A1 L
SO-a
Drawing is not to scale.
14/15
MK41T56, MKI41T56
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics (c) 1999 STMicroelectronics - All Rights Reserved All other names are the property of their respective owners STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com
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