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DS2755 Schematic ( PDF Datasheet ) - Dallas Semiconductor

Teilenummer DS2755
Beschreibung High-Accuracy Battery Fuel Gauge
Hersteller Dallas Semiconductor
Logo Dallas Semiconductor Logo 




Gesamt 20 Seiten
DS2755 Datasheet, Funktion
www.DataSheet4U.com
www.maxim-ic.com
DS2755
High-Accuracy Battery
Fuel Gauge with Snapshot
FEATURES
ƒ Snapshot Mode Allows Instantaneous Power
Measurement
ƒ Accurate Current Measurement for Coulomb
Counting (Current Accumulation)
- 2% ±4μV over ±64mV Input Range
- 2% ±200μA over ±3.2A Range Using a 20mΩ
Sense Resistor
ƒ Current Measurement
- 9-Bit Bidirectional Snapshot Measurement
- 12-Bit Bidirectional Average Updated Every
88ms
- 15-Bit Bidirectional Average Updated Every 2.8s
ƒ Voltage Measurement
- 9-Bit Snapshot Measurement
- 10-Bit Measurement Updated Every 4ms
ƒ Temperature Measurement
- 10-Bit Measurement, 0.125°C Resolution Using
Integrated Sensor
ƒ Host Alerted When Accumulated Current or
Temperature Exceeds User-Selectable Limits
ƒ 96 Bytes of Lockable EEPROM
ƒ 8 Bytes of General-Purpose SRAM
ƒ Dallas 1-Wire® Interface with Unique 64-Bit
Device Address with Standard 16kbps or
Overdrive 142kbps Timing
ƒ 3mm Dimension of 8-Pin TSSOP Package Allows
Mounting on Side of Thin Prismatic Li+ and
Li+/Polymer Cells
APPLICATIONS
Cell Phones
Digital Cameras
Smartphones
PDAs
Portable Consumer Products
PIN CONFIGURATION
VIN 1
VSS 22
PIO 3
VDD 42
8 DQ
7 SNS
6 IS2
5 IS1
DS2755E
8-Pin TSSOP Package
DESCRIPTION
The DS2755 high-precision battery fuel gauge is a
data-acquisition and information-storage device
tailored for cost-sensitive and space-constrained 1-
cell Li+/polymer battery-pack applications. The
DS2755 provides the key hardware components
required to accurately estimate remaining capacity by
integrating low-power, precision measurements of
temperature, voltage, current, and current
accumulation, as well as nonvolatile (NV) data
storage, into the small footprint of a 3.0mm x 4.4mm
8-pin TSSOP package.
Through its 1-Wire interface, the DS2755 gives the
host system read/write access to status and control
registers, instrumentation registers, and general-
purpose data storage. Each device has a unique
factory-programmed 64-bit net address that allows it
to be individually addressed by the host system,
supporting multibattery operation.
ORDERING INFORMATION
PART
DS2755E+
DS2755E+T&R
MARKING
2755
2755
TEMP RANGE
-20°C to +70°C
-20°C to +70°C
1-Wire is a registered trademark of Dallas Semiconductor.
DESCRIPTION
8-Pin TSSOP, Lead Free
DS2755E+ on Tape-and-Reel
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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DS2755 Datasheet, Funktion
DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
CURRENT MEASUREMENT AND ACCUMULATION
The DS2755 current measurement system is designed to provide timely data on charge and discharge current at a
moderate resolution level while simultaneously accumulating high resolution average data to support accurate
coulomb counting. Current is measured with an Analog-to-Digital Converter (ADC) by sampling the voltage drop
across a series sense resistor, RSNS, connected between SNS and VSS. Individual current samples are taken every
687μs (1456-1 Hz). Multiple samples are averaged to report Current and Average Current values, and accumulated
for coulomb counting.
Current Measurement
The voltage signal developed across the sense resistor (between SNS and VSS) is differentially sampled by the
ADC inputs via internal 10kresistors connected between VSS and IS1, and SNS and IS2. Isolating the ADC
inputs (IS1 and IS2 pins) from the sense resistor with 10kΩ facilitates the use of an RC filter by adding a single
external capacitor. The RC filter extends the input range beyond ±64mV in pulse load or pulse charge applications.
The ADC accurately measures large peak signals as long as the differential signal level at IS1 and IS2 does not
exceed ±64mV.
The Current register operates in two modes, normal and snapshot. In normal mode, the Current register reports the
average of 128 individual current samples every 88ms. The reported value represents the average current during
the 88ms measurement period. The Average Current register reports the average of 4096 current samples and is
updated every 2.8s.
In snapshot mode, the Current register holds the current measured immediately following the snapshot trigger.
Current measurements resume immediately after the snapshot value is obtained, however, the SNAP bit must be
cleared to re-enable normal mode current reporting in the Current register. The Average Current register continues
to be updated while the SNAP bit is set. Current accumulation also continues while SNAP is set. Although a small
error is introduced into both the Average Current and Accumulated Current values by the current sample timing
discontinuity introduced with each trigger of the Snapshot mode, use of Snapshot once every 5s does not produce
a significant error.
The following register formats specify the update interval and units for the Current and Average Current registers.
Values are posted in two’s compliment format. Positive values represent charge currents (VIS1 > VIS2) and negative
values represent discharge currents (VIS2 > VIS1). Positive currents above the maximum register value are reported
at the maximum value, 0x7FFF. Negative currents below the minimum register value are reported at the minimum
value, 0x8000.
Figure 3. CURRENT REGISTER FORMAT
DS2755: 12-bit + sign resolution (13-bit), 88ms update interval
MSB—Address 0E
LSB—Address 0F
S 211 210 29 28 27 26 25
MSb
LSb
“S”: sign bit(s)
24 23 22 21 20 X X X
MSb
LSb
Units: 20 = 15.625μV/Rsns
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DS2755 pdf, datenblatt
DS2755: High-Accuracy Battery Fuel Gauge with Snapshot
Figure 9. EEPROM Access via Shadow RAM
Copy
Serial
Interface
Write
Read
EEPROM
Shadow RAM
Recall
Table 1. MEMORY MAP
ADDRESS (HEX)
00
01
02 to 06
07
08
09 to 0B
DESCRIPTION
Reserved
Status Register
Reserved
EEPROM Register
Special Feature Register
Reserved
0C Voltage Register MSB
0D Voltage Register LSB
0E Current Register MSB
0F Current Register LSB
10
11
12 to 17
18
19
1A
1B
1C to 1F
20 to 3F
40 to 5F
60 to 7F
80 to 8F
90 to FF
Accumulated Current Register MSB
Accumulated Current Register LSB
Reserved
Temperature Register MSB
Temperature Register LSB
Average Current Register MSB
Average Current Register LSB
Reserved
EEPROM, block 0
EEPROM, block 1
EEPROM, block 2
SRAM
Reserved
*Each EEPROM block is read/write until locked by the LOCK command, after which it is read-only.
READ/WRITE
R
R/W
R/W
R
R
R
R
R/W
R/W
R
R
R
R
R/W*
R/W*
R/W*
R/W
STATUS REGISTER
The default values for the Status Register bits are stored in lockable EEPROM in the corresponding bits of address
31h. A Recall Data command for EEPROM block 1 recalls the default values into the Status Register bits. The
format of the Status Register is shown in Figure 11. The function of each bit is described in detail in the following
paragraphs.
Figure 11. STATUS REGISTER FORMAT
Address 01
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
X X PMOD RNAOP UVEN IOS OBEN OVD
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