
DS2437
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Applications for the smart battery pack monitor include portable computers, portable/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 battery pack or host system, the DS2437
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 DS2437 EEPROM, and only a software revision is necessary should a designer wish
to change battery pack chemistry.
DETAILED PIN DESCRIPTION
PIN
SYMBOL
1
DQ
3
VAD
5
VSENS+
6
VSENS-
8
AGND
9
GND
11
X2
13
X1
16
V
DD
2, 4, 7, 10,
12, 14, 15
DESCRIPTION
Data Input/Out:
for 1-Wire operation: open drain
ADC Input:
input for general purpose A/D
Battery Input:
connection for battery current to be monitored (see text)
Battery Input:
connection for battery current to be monitored (see text)
Analog Ground:
must be at the same potential as GND
Digital Ground:
must be at the same potential as AGND
Crystal Input:
connection for 32.768 kHz for RTC operation
Crystal Input:
connection for 32.768 kHz for RTC operation
V
DD
Pin:
input supply voltage
No Connect
NC
OVERVIEW
The block diagram of Figure 1 shows the seven major components of the DS2437:
1.
64-bit lasered ROM
2.
temperature sensor
3.
battery voltage A/D
4.
battery current A/D
5.
current accumulators
6.
real-time clock
7.
40-byte nonvolatile user memory
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" for the specifications of these products.
Communication to the DS2437 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 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.