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PDF DS2746 Data sheet ( Hoja de datos )
| Número de pieza | DS2746 | |
| Descripción | Low-Cost 2-Wire Battery Monitor | |
| Fabricantes | Manix | |
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www.maxim-ic.com
DS2746
Low-Cost 2-Wire Battery Monitor
with Ratiometric A/D Inputs
GENERAL DESCRIPTION
The DS2746 provides system-side battery capacity
monitoring in cost-sensitive applications. Voltage,
bidirectional current, and accumulated current
measurement data is provided to the host processor
over a 2-wire interface. Offset bias and offset
blanking features greatly enhance the accuracy of
the coulomb counter. In addition, the DS2746 has
two auxiliary A/D inputs to sample the pack
identification resistor, thermistor, or other voltage
source. The results are reported as a ratiometric
fraction of the supply voltage eliminating error related
to the supply. The DS2746 reduces the total power
consumption of the measurement circuit by enabling
the resistor dividers, through the VOUT pin, only while
measurements are made. When the system is
inactive, a low power sleep mode reduces current
consumption while maintaining the coulomb count.
The tiny 3mm × 3mm TDFN package consumes only
9mm2 of PCB space.
FEATURES
14-Bit Bidirectional Current Measurement
- 6.25μV LSB, ±51.2mV Dynamic Range
- 416.7μA LSB, ±3.4A Range (RSNS = 15mΩ)
Current Accumulation Register Resolution
- 6.25μVhr LSB, 409.6mVh Range
- 417μAhr LSB, 27.31Ah Range
11-Bit Battery Voltage Measurement
- 2.44mV LSB, 0V to 4.997V Input Range
- ±10mV Accuracy at 3.6V Input
Two 11-Bit Aux Input Voltage Measurements
- Ratiometric Inputs Eliminate Supply Error
- VOUT drives Dividers, Reduces Power
- ±8 LSB Accuracy
Low Power Consumption:
- Active Current: 70μA typical, 100μA max
- Sleep Current: 1μA typical, 3μA max
APPLICATIONS
2.5G/3G Wireless Handsets
PDA/Smartphones
Digital Still and Video Cameras
Handheld Computers and Terminals
TYPICAL OPERATING CIRCUIT
ORDERINGwww.DataSheet4U.com INFORMATION
PART
DS2746G+
DS2746G+T&R
TEMP RANGE
-40ºC to +85ºC
-40ºC to +85ºC
PIN-PACKAGE
10-Pin 3mm×3mm
TDFN
DS2746G+ in Tape-
and-Reel
+ Denotes lead-free package.
PIN CONFIGURATION
TOP VIEW
3mm × 3mm TDFN
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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REV: 122706
1 page  
Figure 2. Block Diagram
DS2746 Low-Cost 2-Wire Battery Monitor
DETAILED DESCRIPTION
The DS2746 operates either in active mode where cell voltage, system current, and auxiliary inputs are monitored,
or in a low power sleep mode to conserve energy when the system is idle. While in active mode, the DS2746
contantly measures current flow through an external sense resistor. Each current measurement is reported with
sign and magnitude in a two-byte Current register. Offset bias and offset blanking features remove offset error from
the current A/D to improve measurement accuracy. Each current measurement is integrated into the Accumulated
Current register (ACR) to maintain a sum of all charge entering and exiting the cell.
The DS2746 has two auxiliary inputs to allow voltage sampling of resistor divider circuits. These can be used to
measure a thermistor or an ID resistor located inside the battery pack. The VOUT output provides the pullup voltage
for the resistor divider networks. The DS2746 disables VOUT after measuring the auxiliary inputs to reduce power
use by the measurement system. VOUT operation can be disabled through software to further reduce power
consumption when the auxiliary inputs are not in use.
A dedicated voltage A/D measures voltage of the cell and the auxiliary inputs. A mux on the input to the A/D cycles
through the VIN, AIN0, and AIN1 pins repeatedly in that order. An internal reference is used to measure VIN voltage.
AIN0 and AIN1 are measured as a percentage of VOUT. This ratiometric measurement of the Auxiliary inputs
prevents noise in the supply from affecting accuracy of the readings
The DS2746 measurements can be used directly to provide accurate fuel gauging in typical use conditions, or
along with FuelPack™ algorithms to form a complete and accurate solution for estimating remaining capacity over
wide temperature and operating conditions.
Through its 2-Wire interface, the DS2746 allows a host system read/write access to the Status/Configuration
register and Measurement registers. If sleep mode operation is enabled, holding both interface lines low forces the
DS2746 into a low power sleep mode where A/D measurements are paused and the ACR register is maintained.
FuelPack is a trademark of Dallas Semiconductor.
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5 Page 
DS2746 Low-Cost 2-Wire Battery Monitor
Figure 10. Accumulation Bias Register Format
Address 62h
S 24 23 22 21 20 X X
MSb
“S”: sign bit
LSb
Units: 6.25μVh/Rsns
MEMORY
The DS2746 has memory space with registers for instrumentation, status, and control. When the MSB of a two-
byte register is read, both the MSB and LSB are latched and held for the duration of the read data command to
prevent updates during the read and ensure synchronization between the two register bytes. For consistent results,
always read the MSB and the LSB of a two-byte register during the same read data command sequence.
Table 4. Memory Map
ADDRESS (HEX)
DESCRIPTION
00 Reserved
01 Status/Config Register
02 to 07
Reserved
08 Auxiliary Input 0 Register MSB
09 Auxiliary Input 0 Register LSB
0A Auxiliary Input 1 Register MSB
0B Auxiliary Input 1 Register LSB
0C Voltage Register MSB
0D Voltage Register LSB
0E Current Register MSB
0F Current Register LSB
10 Accumulated Current Register MSB
11 Accumulated Current Register LSB
12 to 60
Reserved
61 Offset Bias Register
62 Accumulation Bias Register
63 to FF
Reserved
READ/WRITE
—
R/W
—
R
R
R
R
R
R
R
R
R/W
R/W
—
R/W
R/W
—
POR DEFAULT
X1110X00b
00h
00h
00h
00h
00h
00h
00h
00h
Undefined
Undefined
00h
00h
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| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet DS2746.PDF ] | |
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