IC MONITOR SMART BATTERY 8-SOIC

DS2438AZ+T&R

Manufacturer Part NumberDS2438AZ+T&R
DescriptionIC MONITOR SMART BATTERY 8-SOIC
ManufacturerMaxim Integrated Products
DS2438AZ+T&R datasheet
 


Specifications of DS2438AZ+T&R

FunctionFuel, Gas Gauge/MonitorBattery TypeSmart Batteries
Voltage - Supply2.4 V ~ 10 VOperating Temperature-40°C ~ 85°C
Mounting TypeSurface MountPackage / Case8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS StatusLead free / RoHS Compliant  
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FEATURES
®
§ Unique 1-Wire
interface requires only one
port pin for communication
§ Provides unique 64-bit serial number
§ Eliminates thermistors by sensing battery
temperature on-chip
§ On-board A/D converter allows monitoring
of battery voltage for end-of-charge and end-
of-discharge determination
§ On-board integrated current accumulator
facilitates fuel gauging
§ Elapsed time meter in binary format
§ 40-byte nonvolatile user memory available
for storage of battery-specific data
§ Reverts to low-power sleep mode on battery
pack disconnect (feature disabled on
DS2438AZ)
§ Operating range -40ºC to +85ºC
§ Applications include portable computers,
portable/cellular phones, consumer
electronics, and handheld instrumentation
DESCRIPTION
The DS2438 Smart Battery Monitor provides several functions that are desirable to carry in a battery
pack: a means of tagging a battery pack with a unique serial number, a direct-to-digital temperature
sensor which eliminates the need for thermistors in the battery pack, an A/D converter which measures
the battery voltage and current, an integrated current accumulator which keeps a running total of all
current going into and out of the battery, an elapsed time meter, and 40 bytes of nonvolatile EEPROM
memory for storage of important parameters such as battery chemistry, battery capacity, charging
methodology and assembly date. Information is sent to/from the DS2438 over a 1-Wire interface, so that
only one wire (and ground) needs to be connected from a central microprocessor to a DS2438. This
means that battery packs need only have three output connectors: battery power, ground, and the 1-Wire
interface.
Because each DS2438 contains a unique silicon serial number, multiple DS2438s can exist on the same
1-Wire bus. This allows multiple battery packs to be charged or used in the system simultaneously.
Applications for the smart battery monitor include portable computers, cellular telephones, and handheld
instrumentation battery packs in which it is critical to monitor real-time battery performance. Used in
conjunction with a microcontroller in the host system, the DS2438 provides a complete smart battery
pack solution that is fully chemistry-independent. The customization for a particular battery chemistry
and capacity is realized in the code programmed into the microcontroller and DS2438 EEPROM, and
only a software revision is necessary should a designer wish to change battery pack chemistry.
Smart Battery Monitor
PIN ASSIGNMENT
GND
1
8
V
2
7
SENS+
V
3
6
SENS-
V
4
5
AD
DS2438Z, DS2438AZ
8-Pin SOIC (150-mil)
PIN DESCRIPTION
DQ
-
Data In/Out
VAD
-
General A/D input
V
-
Battery current monitor input (+)
SENS+
V
-
Battery current monitor input (-)
SENS-
VDD
-
Power Supply (2.4V to 10.0V)
GND
-
Ground
NC
-
No connect
1 of 29
DS2438
DQ
NC
NC
V
DD
070605

DS2438AZ+T&R Summary of contents

  • Page 1

    FEATURES ® § Unique 1-Wire interface requires only one port pin for communication § Provides unique 64-bit serial number § Eliminates thermistors by sensing battery temperature on-chip § On-board A/D converter allows monitoring of battery voltage for end-of-charge and ...

  • Page 2

    ORDERING INFORMATION PART DS2438Z+ DS2438Z+T&R DS2438AZ+ DS2438AZ+T&R DS2438Z DS2438Z/T&R DS2438AZ DS2438AZ/T&R + Denotes lead-free package. DETAILED PIN DESCRIPTION PIN SYMBOL 1 GND 2 V SENS SENS OVERVIEW ...

  • Page 3

    Control function commands may be issued which instruct the DS2438 to perform a temperature measurement or battery voltage A/D conversion. The result of these measurements will be placed in the DS2438’s memory map, and may be read by issuing a ...

  • Page 4

    OPERATION-MEASURING TEMPERATURE The DS2438 measures temperatures through the use of an on-board temperature measurement technique. The temperature reading is provided in a 13-bit, two’s complement format, which provides 0.03125°C of resolution. Table 1 describes the exact relationship of output data ...

  • Page 5

    VOLTAGE REGISTER FORMAT Table MSb 0 BATTERY VOLTAGE 0.05V 2.7V 3.6V 5V 7.2V 9.99V 10V For applications requiring a general purpose voltage A/D converter, the DS2438 can be configured so that the result of a Convert ...

  • Page 6

    CURRENT REGISTER FORMAT Table 3 (This register actually stores the voltage measured across current sense resistor R This value can be used to calculate battery pack current using the equation below MSb S The battery pack current ...

  • Page 7

    OPERATION - CURRENT ACCUMULATORS The DS2438 tracks the remaining capacity of a battery using the Integrated Current Accumulator (ICA). The ICA maintains a net accumulated total of current flowing into and out of the battery; therefore, the value stored in ...

  • Page 8

    THRESHOLD REGISTER FORMAT Table 6 MSb TH2 The Charging Current Accumulator (CCA two-byte nonvolatile read/write counter which represents the total charging current the battery has encountered in its lifetime only updated when ...

  • Page 9

    Figure 2 illustrates the activity of the ICA, CCA, and DCA over a sample charge/discharge cycle of a battery pack, assuming the DS2438 is configured for the ICA to function and the CCA/DCA to function and shadow data to EEPROM. ...

  • Page 10

    Two other time-related functions are available. The first is the Disconnect Timestamp, which is written to by the DS2438 whenever it senses that the DQ line has been low for approximately 2 seconds. This condition would signal that the battery ...

  • Page 11

    LASERED ROM FORMAT Figure 3 8-BIT CRC CODE MSb LSb CRC Generation The DS2438 has an 8-bit CRC stored in the most significant byte of the 64-bit ROM. The bus master can compute a CRC value from the first ...

  • Page 12

    ROM FUNCTIONS FLOWCHART Figure ...

  • Page 13

    MEMORY/CONTROL FUNCTIONS FLOWCHART Figure YES ...

  • Page 14

    MEMORY/CONTROL FUNCTIONS FLOWCHART Figure 6 (continued) MEMORY MAP The DS2438’s memory is organized as shown in Figure 7. The memory consists of a scratchpad RAM and storage SRAM/EEPROM. The scratchpad helps insure data integrity when communicating over the 1-Wire bus. ...

  • Page 15

    Page 0 (00h) The first page contains the most frequently accessed information of the DS2438, and most locations are volatile read-only bytes with the exception of the Status/Configuration Register (Byte 0) and the Threshold Register (Byte 7). The Status/Configuration Register ...

  • Page 16

    Page 1 (01h) The second page, Page 1, contains the ICA, elasped time meter, and current offset data. Both the ETM and ICA are volatile read/write locations so that they may be set, changed, or cleared by the host software. ...

  • Page 17

    BUS SYSTEM The 1-Wire bus is a system which has a single bus master and one or more slaves. The DS2438 behaves as a slave. The discussion of this bus system is broken down into three topics: hardware configuration, ...

  • Page 18

    ROM FUNCTION COMMANDS Once the bus master has detected a presence, it can issue one of the four ROM function commands. All ROM function commands are 8-bits long. A list of these commands follows (refer to flowchart in Figure 5): ...

  • Page 19

    The bus master reads a bit from the 1-Wire bus. Each device will respond by placing the value of the first bit of their respective ROM data onto the 1-Wire bus. ROM1 and ROM4 will place a 0 onto ...

  • Page 20

    The bus master writes a 0 bit. This decouples ROM3, and leaving only ROM2. 17. The bus master reads the remainder of the ROM bits for ROM2 and communicates to the underlying logic if desired. This completes the third ...

  • Page 21

    Recall Memory [B8hxxh] This command recalls the stored values in EEPROM / SRAM page xxh to the scratchpad page xxh. This command must proceed a Read SPxx command in order to read any page of memory on the DS2438. Valid ...

  • Page 22

    NOTES: 1. Temperature conversion takes ms. 2. A/D conversion takes ms. 3. EEPROM writes take ms. SAMPLE COMMAND SEQUENCE Table 12 Example: Bus Master enables the ICA, CCA, and DCA on ...

  • Page 23

    SAMPLE COMMAND SEQUENCE Table 13 Example: Bus Master issues a temperature and voltage conversion, then reads the temperature, battery voltage, battery current, all on a single DS2438. MASTER MODE DATA (LSB FIRST ...

  • Page 24

    SAMPLE COMMAND SEQUENCE Table 14 Example: Assuming a single DS2438 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 ...

  • Page 25

    INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 9 RESISTOR MASTER DS2438 Write Time Slots A write time slot is initiated when the host pulls the data line from a high (inactive) logic level to a low logic level. There are ...

  • Page 26

    READ / WRITE TIMING DIAGRAM Figure 10 Write-One Time Slot RESISTOR MASTER Write-Zero Time Slot Read-Data Time Slot RESISTOR MASTER DS2438 DS2438 SAMPLING WINDOW 60 ms £ t < 120 ms SLOT 1 ms £ t < LOW1 ...

  • Page 27

    ABSOLUTE MAXIMUM RATINGS* Voltage on VDD and VAD, Relative to Ground Voltage on VSENS+, VSENS-, Relative to Ground Voltage on Any Other Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature * This is a stress rating only and ...

  • Page 28

    ELECTRICAL CHARACTERISTICS: DIGITAL THERMOMETER PARAMETER Thermometer Error (T - ACTUAL T ) MEASURED Conversion Time ELECTRICAL CHARACTERISTICS: VOLTAGE A/D CONVERTER PARAMETER A/D Error V Input Range AD V Input Range DD Conversion Time No Missing Code Temperature Range ELECTRICAL CHARACTERISTICS: ...

  • Page 29

    AC ELECTRICAL CHARACTERISTICS: NV MEMORY PARAMETER NV Write Cycle Time EEPROM Writes (copy scratchpad command) EEPROM data retention AC ELECTRICAL CHARACTERISTICS: 1-WIRE INTERFACE PARAMETER Time Slot Recovery Time Write 0 Low Time Write 1 Low Time Read Data Valid Reset ...