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PDF DS2778 Data sheet ( Hoja de datos )
| Número de pieza | DS2778 | |
| Descripción | 2-Cell Stand-Alone Li+ Fuel-Gauge IC | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-4688; Rev 3; 5/10
www.DataSheet4U.com
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
General Description
The DS2775–DS2778 report available capacity for
rechargeable lithium-ion (Li+) and Li+ polymer (Li-Poly)
batteries in mAh and as a percentage of full. Safe oper-
ation is ensured by the integrated Li+ protector. The
DS2776/DS2778 support SHA-1-based challenge-
response authentication in addition to all other DS2775/
DS2777 features.
Precision measurements of voltage, temperature, and
current, along with a cell characteristics table and
application parameters, are used for capacity estima-
tion calculations. The capacity registers report a con-
servative estimate of the amount of charge that can be
removed given the current temperature, discharge rate,
stored charge, and application parameters.
The DS2775–DS2778 operate from +4.0V to +9.2V for
direct integration into battery packs with two Li+ or Li-
Poly cells.
In addition to nonvolatile storage for cell compensation
and application parameters, the DS2775–DS2778 offer
16 bytes of EEPROM for use by the host system and/or
pack manufacturer to store battery lot and date tracking
information. The EEPROM can also be used for non-
volatile storage of system and/or battery usage statis-
tics. A Maxim 1-Wire® (DS2775/DS2776) or 2-wire
(DS2777/DS2778) interface provides serial communica-
tion to access measurement and capacity data regis-
ters, control registers, and user memory. The
DS2776/DS2778 use the SHA-1 hash algorithm in a
challenge-response pack authentication protocol for
battery-pack verification.
Applications
Low-Cost Notebooks
UMPCs
DSLR Cameras
Video Cameras
Commercial and Military Radios
Portable Medical Equipment
Selector Guide appears at end of data sheet.
Features
♦ High-Side nFET Drivers and Protection Circuitry
♦ Precision Voltage, Temperature, and Current
Measurement System
♦ Cell-Capacity Estimation from Coulomb Count,
Discharge Rate, Temperature, and Cell
Characteristics
♦ Estimates Cell Aging Between Learn Cycles
♦ Uses Low-Cost Sense Resistor
♦ Allows Calibration of Gain and Temperature
Coefficient
♦ Programmable Thresholds for Overvoltage and
Overcurrent
♦ Pack Authentication Using SHA-1 Algorithm
(DS2776/DS2778)
♦ 32-Byte Parameter EEPROM
♦ 16-Byte User EEPROM
♦ Maxim 1-Wire Interface with 64-Bit Unique ID
(DS2775/DS2776)
♦ 2-Wire Interface with 64-Bit Unique ID
(DS2777/DS2778)
♦ 3mm x 5mm, 14-pin TDFN Lead-Free Package
Ordering Information
PART
PIN-PACKAGE
TOP MARK
DS2775G+
14 TDFN-EP*
D2775
DS2775G+T&R
14 TDFN-EP*
D2775
DS2776G+
14 TDFN-EP*
D2776
DS776G+T&R
14 TDFN-EP*
D2776
DS2777G+
14 TDFN-EP*
D2777
DS2777G+T&R
14 TDFN-EP*
D2777
DS2778G+
14 TDFN-EP*
D2778
DS2778G+T&R
14 TDFN-EP*
D2778
Note: All devices are specified over the -20°C to +70°C oper-
ating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
*EP = Exposed pad.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
www.DataSheet4U.com
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
ELECTRICAL CHARACTERISTICS: 2-WIRE INTERFACE (DS2777/DS2778 ONLY)
(VDD = +4.0V to +9.2V, TA = -20°C to +70°C.)
PARAMETER
SCL Clock Frequency
Bus-Free Time Between a STOP
and START Condition
SYMBOL
fSCL
(Note 4)
tBUF
CONDITIONS
MIN TYP MAX UNITS
0 400 kHz
1.3 μs
Hold Time (Repeated) START
Condition
Low Period of SCL Clock
High Period of SCL Clock
Setup Time for a Repeated
START Condition
Data Hold Time
Data Setup Time
Rise Time of Both SDA and SCL
Signals
Fall Time of Both SDA and SCL
Signals
Setup Time for STOP Condition
Spike Pulse Widths Suppressed
by Input Filter
tHD:STA (Note 5)
tLOW
tHIGH
tSU:STA
tHD:DAT
tSU:DAT
(Notes 6, 7)
(Note 6)
tR
tF
tSU:STO
tSP (Note 8)
0.6
1.3
0.6
0.6
0
100
20 +
0.1CB
20 +
0.1CB
0.6
0
μs
μs
μs
μs
0.9 μs
ns
300 ns
300 ns
μs
50 ns
Capacitive Load for Each Bus
Line
SCL, SDA Input Capacitance
CB
CBIN
(Note 9)
400 pF
60 pF
Note 1: Accumulation bias and offset bias registers set to 00h. NBEN bit set to 0.
Note 2: Measurement made with VSRC = +8V, VGS driven with external +4.5V supply.
Note 3: Overvoltage (OV) and undervoltage (UV) delays (tOVD, tUVD) are reduced to zero seconds if the OV or UV condition is
detected within 100ms of entering active mode.
Note 4: Timing must be fast enough to prevent the DS2777/DS2778 from entering sleep mode due to bus low for period > tSLEEP.
Note 5: fSCL must meet the minimum clock low time plus the rise/fall times.
Note 6: The maximum tHD:DAT need only be met if the device does not stretch the low period (tLOW) of the SCL signal.
Note 7: This device internally provides a hold time of at least 75ns for the SDA signal (referred to the VIHMIN of the SCL signal) to
bridge the undefined region of the falling edge of SCL.
Note 8: Filters on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
Note 9: CB is total capacitance of one bus line in pF.
_______________________________________________________________________________________ 5
5 Page 
www.DataSheet4U.com
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
Detailed Description
The DS2775–DS2778 function as an accurate fuel
gauge, Li+ protector, and SHA-1-based authentication
token (SHA-1-based authentication available only on
the DS2776/DS2778). The fuel gauge provides accu-
rate estimates of remaining capacity and reports timely
voltage, temperature, and current measurement data.
Capacity estimates are calculated from a piecewise lin-
ear model of the battery performance over load and
temperature along with system parameters for charge
and end-of-discharge conditions. The algorithm para-
meters are user programmable and can be modified
within the pack. Critical capacity and aging data are
periodically saved to EEPROM in case of short-circuit
or deep-depletion events.
The Li+ protection function ensures safe, high-perfor-
mance operation. nFET protection switches are driven
with a charge pump that maintains gate drive as the
cell voltage decreases. The high-side topology pre-
serves the ground path for serial communication while
eliminating the parasitic charge path formed when the
fuel-gauge IC is located inside the protection FETs in a
low-side configuration. The thresholds for overvoltage,
undervoltage, overcurrent, and short-circuit current are
user programmable for customization to each cell and
application.
The 32-bit-wide SHA-1 engine with 64-bit secret and
64-bit challenge words resists brute force and other
attacks with financial-level HMAC security. The chal-
lenge of managing secrets in the supply chain is
addressed with the compute next secret feature. The
unique serial number or ROM ID can be used to assign
a unique secret to each battery.
Power Modes
The DS2775–DS2778 have two power modes: active
and sleep. On initial power-up, the DS2775–DS2778
default to active mode. In active mode, the DS2775–
DS2778 are fully functional with measurements and
capacity estimation registers continuously updated.
The protector circuit monitors battery pack, cell volt-
ages, and battery current for safe conditions. The pro-
tection FET gate drivers are enabled when conditions
are deemed safe. Also, the SHA-1 authentication func-
tion is available in active mode. When an SHA-1 com-
putation is performed, the supply current increases to
IDD2 for tSHA. In sleep mode, the DS2775–DS2778 con-
serve power by disabling measurement and capacity
estimation functions, but preserve register contents.
Gate drive to the protection FETs is disabled in sleep;
the SHA-1 authentication feature is not operational.
The IC enters sleep mode under two different condi-
tions: bus low and undervoltage. An enable bit makes
entry into sleep optional for each condition. Sleep mode
is not entered if a charger is connected (VPLS > VDD +
VCD) or if a charge current of 1.6mV/RSNS measured
from SNS to VSS. The DS2775–DS2778 exit sleep mode
upon charger connection or a low-to-high transition on
any communication line. The bus-low condition, where
all communication lines are low for tSLEEP, indicates
pack removal or system shutdown in which the bus
pullup voltage, VPULLUP, is not present. The power
mode (PMOD) bit must be set to enter sleep when a
bus-low condition occurs. After the DS2775–DS2778
enter sleep due to a bus-low condition, it is assumed
that no charge or discharge current flows and that
coulomb counting is unnecessary.
The second condition to enter sleep is an undervoltage
condition, which reduces battery drain due to the
DS2775–DS2778 supply current and prevents overdis-
charging the cell. The DS2775–DS2778 transition to
sleep mode if the VIN1 or VIN2 voltage is less than VUV
and the undervoltage enable (UVEN) bit is set. The
communication bus must be in a static state, that is,
with DQ (SDA and SCL for 2-wire) either high or low for
tSLEEP. The DS2775–DS2778 transition from sleep
mode to active mode when DQ (SDA and SCL for
2-wire) changes logic state. See Figures 1 and 2 for
more information on sleep-mode state.
The DS2775–DS2778 have a “power switch” capability
for waking the device and enabling the protection FETs
when the host system is powered down. A simple dry
contact switch on the PIO pin or DQ pin can be used to
wake up the battery pack. The power-switch function is
enabled using the PSPIO and PSDQ configuration bits
in the Control register.
When PSPIO or PSDQ are set and sleep mode is
entered through the PMOD condition*, the PIO and DQ
pins pull high, respectively. Sleep mode is exited upon
the detection of a low-going transition on PIO or DQ.
PIO has a 100ms debounce period to filter out glitches
that can be caused when a sleeping battery is inserted
into a system.
*The “power switch” feature is disabled if sleep mode is
entered because of a UV condition.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet DS2778.PDF ] | |
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