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PDF DS2437 Data sheet ( Hoja de datos )
| Número de pieza | DS2437 | |
| Descripción | Smart Battery Monitor | |
| Fabricantes | Dallas Semiconducotr | |
| Logotipo |  |
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DS2437
Smart Battery Monitor
FEATURES
Unique 1-Wire® interface requires only one
PIN ASSIGNMENT
port pin for communication
Provides unique 64-bit serial number to
battery packs
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
DQ
NC
VAD
NC
VSENS+
VSENS-
NC
AGND
1
2
3
4
5
6
7
8
16 VDD
15 NC
14 NC
13 X1
12 NC
11 X2
10 NC
9 GND
16-PIN SSOP
See Mech. Drawings Section
facilitates gas gauging
Real-time clock in binary format
40-byte nonvolatile user memory available for
storage of user data such as gas gauge and
manufacturing information
Operating range -40°C to +85°C
Applications include portable computers,
portable/cellular phones, consumer
electronics, and handheld instrumentation
PIN DESCRIPTION
DQ - Data In/Out
VAD
- General A/D input
VSENS+ - Battery current monitor input (+)
VSENS- - Battery current monitor input (-)
NC - No connect
GND
- Digital Ground
AGND - Analog Ground
X2 - Connection for 32.768 kHz XTAL
X1 - Connection for 32.768 kHz XTAL
VDD - Power Supply (2.7V to 10.0V)
DESCRIPTION
The DS2437 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; a real-time clock; and 40 bytes of nonvolatile EEPROM
memory for storage of important parameters such as battery capacity, capacity remaining, and indication
of battery cycling.
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.
Because each DS2437 contains a unique silicon serial number, multiple DS2437s can exist on the same
1-Wire bus. This allows multiple battery packs to be charged or used in the system simultaneously.
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DS2437
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.
Voltage/Data Relationships Table 2
BATTERY
VOLTAGE
0.01V
2.7
3.6V
5V
7.2V
9.99V
10V
DIGITAL OUTPUT (Binary)
0000 0000 0000 0001
0000 0001 0000 1110
0000 0001 0110 1000
0000 0001 1111 0100
0000 0010 1101 0000
0000 0011 1110 0111
0000 0011 1110 1000
DIGITAL OUTPUT (Hex)
0001h
010Eh
0168h
01F4h
02D0h
03E7h
03E8h
For applications requiring a general purpose voltage A/D converter, the DS2437 can be configured so that
the result of a Convert V command will place the scaled binary representation of the voltage on the VAD
input (as opposed to the VDD input) into the VOLTAGE REGISTER in the same format described in
Table 2. Depending upon the state of the configuration register, either (but not both) the VDD or VAD
voltage will be stored in the VOLTAGE REGISTER upon receipt of the Convert V command. Refer to
the description of the Configuration Register in the Memory Map section for details. If the VAD input is
used as the voltage input, the A/D will be accurate for 0V < VAD < 2VDD over the range 2.7V < VDD <
5.0V. Recall that the battery voltage A/D (VDD input) loses accuracy as VDD falls below 2.7V. This
feature gives the user the ability to have a voltage A/D that meets spec accuracy for inputs over the entire
range of 0V < VAD < 10V for VDD = 5.0V.
OPERATION – MEASURING BATTERY CURRENT
The DS2437 features a sigma-delta A/D converter that effectively measures the current flow into and out
of the battery pack. It does so in the background at a rate of 32 measurements/sec; thus, no command is
required to initiate current flow measurements. However, the DS2437 will only perform current A/D
measurements if the IAD bit is set to 1 in the CONFIGURATION REGISTER. The DS2437 measures
current flow in and out of the battery through the VSENS pins; the voltage from the VSENS+ pin to the
VSENS- pin is considered to be the voltage across the current sense resistor, RSENS. While the VSENS+
terminal may be tied directly to the cell side of the RSENS resistor, we recommend using an RC low pass
filter between the other side of RSENS and VSENS-. Using a 47 kΩ=(max) resistor (RF) and a 0.1 µF
capacitor (CF), the filter cutoff is approximately 32 Hz. The current A/D measures at a rate of 32 times
per second, or once every 31.25 ms. This filter will capture the effect of many current spikes and will thus
allow the current accumulators to accurately reflect the total charge which has gone into or out of the
battery.
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5 Page 
1-Wire CRC CODE Figure 4
ROM FUNCTIONS FLOWCHART Figure 5
DS2437
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet DS2437.PDF ] | |
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