DS2438 Smart Battery Monitor FEATURES PIN ASSIGNMENT Unique 1-Wire interface requires only one port pin for communication GND 1 8 DQ Provides unique 64-bit serial number V NC SENS+ 2 7 Eliminates thermistors by sensing battery temperature on-chip V 3 6 NC SENS- On-board A/D converter allows monitoring V AD 4 5 V DD of battery voltage for end-of-charge and end- of-discharge determination DS2438Z, DS2438AZ On-board integrated current accumulator 8-Pin SOIC (150-mil) facilitates fuel gauging Elapsed time meter in binary format PIN DESCRIPTION 40-byte nonvolatile user memory available DQ - Data In/Out for storage of battery-specific data VAD - General A/D input Reverts to low-power sleep mode on battery V - Battery current monitor input (+) SENS+ pack disconnect (feature disabled on V - Battery current monitor input (-) SENS- DS2438AZ) VDD - Power Supply (2.4V to 10.0V) Operating range -40C to +85C GND - Ground Applications include portable computers, NC - No connect 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 Functional Diagrams 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 Pin Configurations appear at end of data sheet. conjunction with a microcontroller in the host system, the DS2438 provides a complete smart battery Functional Diagrams continued at end of data sheet. pack solution that is fully chemistry-independent. The customization for a particular battery chemistry UCSP is a trademark of Maxim Integrated Products, Inc. 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. 1 of 29 For pricing, delivery, and ordering information, please contact Maxim Direct 070605 at 1-888-629-4642, or visit Maxims website at www.maximintegrated.com. AVAILABLEDS2438 ORDERING INFORMATION PART MARKING PACKAGE INFORMATION DS2438Z+ DS2438 8-Pin SOIC DS2438Z+T&R DS2438 DS2438Z+ on Tape-and-Reel DS2438AZ+ DS2438A 8-Pin SOIC DS2438AZ+T&R DS2438A DS2438AZ+ on Tape-and-Reel DS2438Z DS2438 8-Pin SOIC DS2438Z/T&R DS2438 DS2438Z on Tape-and-Reel DS2438AZ DS2438A 8-Pin SOIC DS2438AZ/T&R DS2438A DS2438AZ on Tape-and-Reel + Denotes lead-free package. DETAILED PIN DESCRIPTION PIN SYMBOL DESCRIPTION 1 GND Ground 2 V Battery Input: connection for battery current to be monitored (see text) SENS+ 3 V Battery Input: connection for battery current to be monitored (see text) SENS- 4 V ADC Input: input for general purpose A/D AD 5 V V Pin: input supply voltage DD DD 6, 7 NC No Connect 8 DQ Data Input/Out: for 1-Wire operation: Open drain OVERVIEW The block diagram of Figure 1 shows the seven major components of the DS2438: 1. 64-bit lasered ROM 2. temperature sensor 3. battery voltage A/D 4. battery current A/D 5. current accumulators 6. elapsed time meter 7. 40-byte nonvolatile user-memory Each DS2438 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 for the specifications of these products. Communication to the DS2438 is via a 1-Wire port. With the 1-Wire port, the memory and control functions will not be available until the ROM function protocol has been established. The master must first provide one of four ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, or 4) Skip ROM. These commands operate on the 64-bit lasered ROM portion of each device and can singulate a specific device if many are present on the 1-Wire line as well as to indicate to the bus master how many and what types of devices are present. After a ROM function sequence has been successfully executed, the memory and control functions are accessible and the master may then provide any one of the six memory and control function commands. 2 of 29