ds2437 Maxim Integrated Products, Inc., ds2437 Datasheet
ds2437
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ds2437 Summary of contents
Page 1
... Information is sent to/from the DS2437 over a 1-Wire interface, so that only one wire (and ground) needs to be connected from a central microprocessor to a DS2437. This means that battery packs need only have three output connectors: battery power, ground, and the 1-Wire interface ...
Page 2
... Each DS2437 contains a unique 64-bit lasered ROM serial number so that several battery packs can be charged/monitored by the same host system. Furthermore, other Dallas products featuring the same 1-Wire bus architecture with a 64-bit ROM can reside on the same bus; refer to the Dallas "Automatic Identification Data Book" ...
Page 3
... DS2437 memory map and can be extracted with a control function command. The nonvolatile user memory of the DS2437 consists of 40 bytes of EEPROM. These locations may be used to store any data the user wishes and are written to using a memory function command. All data and commands are read and written least significant bit first ...
Page 4
... While the ADC has a range that extends to 0V important to note that the battery voltage can also be the supply voltage to the DS2437. As such, the accuracy of the ADC begins to degrade below battery voltages of 2.7V, and the ability to make conversions is limited by the operating voltage range of the DS2437 ...
Page 5
... Voltage is expressed in this register in scaled binary format, as outlined in Table 2. Note that while codes exist for values below 2.7V, accuracy of the ADC and the limitation on the DS2437’s supply voltage make it unlikely that these values would be used in actual practice. See “Memory Map” section for the VOLTAGE REGISTER address location ...
Page 6
... For the DS2437 to output current data scaled as in Table 3, the user is responsible for selecting an R that will provide a 100 mV drop across rate. However, this value could be changed to correspond to a different rate as long as this is comprehended by the user’s software in interpreting the results from the DS2437. OPERATION – ...
Page 7
... DS2437 is properly configured, thus allowing three EEPROM updates for each complete discharge cycle of the battery pack. Table 5 illustrates the contents of the CCA/DCA registers. In reference to the CCA/DCA, the DS2437 can be configured to function in any of three modes. Refer to the Memory Map section for details of device configuration and for the address location of the CCA/DCA ...
Page 8
... Figure 2 below illustrates the activity of the ICA, CCA, and DCA over a sample charge/discharge cycle of a battery pack, assuming the DS2437 is configured for the ICA to function and the CCA/DCA to function and shadow data to EEPROM. To simplify the illustration of the accumulators, they are treated as analog values, although they are digital counters in the DS2437 ...
Page 9
... Two other time-related functions are available. The first is the DISCONNECT TIMESTAMP, which is written to by the DS2437 whenever it senses that the DQ line has been low for more than 1 second. This condition would signal that the battery pack has been removed from the system; the time when that ...
Page 10
... Each DS2437 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code (DS2437 code is 1Eh). The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. (See Figure 3.) The 64-bit ROM and ROM Function Control section allow the DS2437 to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section “ ...
Page 11
... CRC CODE Figure 4 ROM FUNCTIONS FLOWCHART Figure DS2437 ...
Page 12
... MEMORY/CONTROL FUNCTIONS FLOWCHART Figure DS2437 YES ...
Page 13
... MEMORY/CONTROL FUNCTIONS FLOWCHART Figure 6 Cont'd DS2437 RECALLS EEPROM PAGE INTO SP PAGE DS2437 X X ...
Page 14
... CA bit in the status/configuration register is set to 0, the E2? bit will have no effect on the DS2437 functionality Voltage A/D Input Select Bit the battery input (VDD) is selected as the input for the DS2437 voltage A/D converter the general purpose A/D input (VAD) is selected as the voltage A/D input. For either setting, a Convert V command will initialize a voltage A/D conversion. ...
Page 15
... Real Time Clock” section for the formatting of these locations. Pages 3-7 (03h - 07h) The remainder of the memory in the DS2437 (Pages 3 through 7) is backed with EEPROM. This memory provides 40 bytes of user memory which may be used to carry any information the user wishes to store. ...
Page 16
... DS2437 MEMORY MAP Figure 7 1-Wire BUS SYSTEM The 1-Wire bus is a system which has a single bus master and one or more slaves. The DS2437 behaves as a slave. The discussion of this bus system is broken down into three topics: hardware configuration, transaction sequence, and 1-Wire signaling (signal types and timing). ...
Page 17
... The presence pulse lets the bus master know that the DS2437 is on the bus and is ready to operate. For more details, see the “1-Wire Signaling” section. ...
Page 18
... The bus master then writes keep both ROM1 and ROM4 coupled. 7. The bus master executes two reads and receives two 0-bits. This indicates that both 1-bits and 0-bits rd exist as the 3 bit of the ROM data of the attached devices. ROM1 = 00110101... ROM2 = 10101010... ROM3 = 11110101... ROM4 = 00010001... DS2437 ...
Page 19
... After issuing this command, the user must send the page number of the scratchpad to be written; then the user may begin writing data to the DS2437 scratchpad. Writing may be terminated at any point by issuing a reset. Valid page numbers for writing are 00h-07h. ...
Page 20
... While an A/D conversion is taking place, all other memory functions are still available for use. If the bus master issues read time slots following this command, the DS2437 will output 0 on the bus as long busy making a voltage measurement; it will return a 1 when the conversion is complete. ...
Page 21
... EEPROM write takes ms. Sample Command Sequence Table 7 Example: Bus Master enables the ICA, CCA, and DCA on a single DS2437 and configures it such that the CCA/DCA information is shadowed to EEPROM. The voltage A/D is configured such that the DS2437 will perform voltage measurements on the battery (VDD) voltage. ...
Page 22
... Sample Command Sequence Table 8 Example: Bus Master issues a temperature and voltage conversion, then reads the temperature, battery voltage, battery current, all on a single DS2437. MASTER MODE DATA (LSB FIRST Presence Presence Presence TX TX B8h00h TX RX Presence ...
Page 23
... Sample Command Sequence Table 9 Example: Assuming a single DS2437 is configured for its current accumulators to function, this sequence allows the Bus Master to read the three current accumulators. MASTER MODE DATA (LSB FIRST Presence TX TX B8h01h TX RX Presence TX TX BEh01h RX <9 data bytes> ...
Page 24
... The DS2437 samples the I/O line in a window after the I/O line falls. If the line is high, a Write 1 occurs. If the line is low, a Write 0 Occurs (See Figure 10). ...
Page 25
... The host generates read time slots when data read from the DS2437. A read time slot is initiated when the host pulls the data line from a logic high level to logic low level. The data line must remain at a low logic level for a minimum output data from the DS2437 is then valid within the next 14 s maximum. ...
Page 26
... READ / WRITE TIMING DIAGRAM Figure DS2437 ...
Page 27
... DETAILED MASTER READ 1 TIMING Figure 11 RECOMMENDED MASTER READ 1 TIMING Figure DS2437 ...
Page 28
... See J-STD-020A specification V 10.0V) DD TYP MAX UNITS NOTES 10.0 V +5.5 V 5.5 GND V +0.5 V 10.0V) DD TYP MAX UNITS NOTES V 0 100 A 250 1000 A 500 k V 10.0V) DD TYP MAX UNITS NOTES bits 400 1000 ms DS2437 ...
Page 29
... CONDITION MIN ERR ERR (- +85 C; 2.7V CONDITION MIN ERR TYP MAX UNITS 10 bits 2 ms +85 C Guaranteed V DD TYP MAX UNITS LSB bits V DD TYP MAX UNITS 1 sec DS2437 10.0V) NOTES 10.0V) NOTES 1 10.0V) NOTES 6 ...
Page 30
... INTERNAL GROUND CONNECTIONS Figure 13 (- +85 C; 2.7V CONDITION MIN SLOT REC RDV 480 480 RSTL PDH CONDITION MIN PDL TYP MAX UNITS 60 120 120 TYP MAX UNITS 60 240 DS2437 10.0V) DD NOTES NOTES ...
Page 31
... TIMING DIAGRAMS Figure 14 1-WIRE WRITE 1 TIME SLOT 1-WIRE WRITE 0 TIME SLOT 1-WIRE READ TIME SLOT 1-WIRE RESET PULSE 1-WIRE PRESENCE DETECT DS2437 ...