Rainbow Electronics DS2788 - Manual (Page 6)

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8 Detailed Description
The DS2788 operates directly from 2.5V to 5.5V and
supports single-cell Li+ battery packs. As shown in
Figure 2, the DS2788 accommodates multicell applica-
tions by adding a trim resistor for calibration of an
external voltage-divider for V IN . NV storage is provided
for cell compensation and application parameters.
Host-side development of fuel-gauging algorithms is
eliminated. On-chip algorithms and convenient status
reporting of operating conditions reduce the serial
polling required of the host processor.
Additionally, 16 bytes of EEPROM memory are made
available for the exclusive use of the host system
and/or pack manufacturer. The additional EEPROM
memory can be used to facilitate battery lot and date
tracking and NV storage of system or battery usage
statistics.
A 1-Wire interface provides serial communication at the
standard 16kbps or overdrive 140kbps speeds, allow-
ing access to data registers, control registers, and user
memory. A unique, factory-programmed, 64-bit regis-
tration number (8-bit family code + 48-bit serial number
+ 8-bit CRC) assures that no two parts are alike and
enables absolute traceability. The 1-Wire interface on
the DS2788 supports multidrop capability so that multi-
ple slave devices can be addressed with a single pin.
Power Modes
The DS2788 has two power modes: ACTIVE and
SLEEP. On initial power-up, the DS2788 defaults to
ACTIVE mode. While in ACTIVE mode, the DS2788 is
fully functional with measurements and capacity esti-
mation continuously updated. In SLEEP mode, the
DS2788 conserves power by disabling measurement
and capacity estimation functions, but preserves regis-
ter contents. SLEEP mode is entered under two differ-
ent conditions and an enable bit for each condition
makes entry into SLEEP optional. SLEEP mode can be
enabled using the power mode (PMOD) bit or the
undervoltage enable (UVEN) bit.
The PMOD type SLEEP is entered if the PMOD bit is set
and DQ is low for t SLEEP (2s nominal). The condition of
DQ low for t SLEEP can be used to detect a pack discon-
Stand-Alone Fuel-Gauge IC with
LED Display Drivers
6 _______________________________________________________________________________________
DS2788
LED1
LED2
LED3
LED4
LED5
DQ
SNS
PIO
V DD
VMA
B3F-1000
150 Ω
5.6V
BSS84
2N7002
0.1 µF
0.1 µF
10 µF 100k Ω
10k Ω
10k Ω
900k Ω
PROTECTION
CIRCUIT
10-CELL
Li+ BATTERY
V IN
OVD
DV
SS
V SS
PK+
330 Ω 330 Ω 330 Ω 330 Ω 330 Ω
LEDs
DATA
R SNS
20m Ω
PK-
MAX6765TTLD2+
RST GND
OUT TIMEOUT
IN ENABLE
Figure 2. Multicell Application Example