Datasheet

DS2775/DS2776/DS2777/DS2778
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
12 ______________________________________________________________________________________
Li+ Protection Circuitry
During active mode, the DS2775–DS2778 constantly
monitor SNS, V
IN1
, V
IN2
, and PLS to protect the battery
from overvoltage (overcharge), undervoltage (overdis-
charge), and excessive charge and discharge currents
(overcurrent, short circuit). Table 1 summarizes the
conditions that activate the protection circuit, the
response of the DS2775–DS2778, and the thresholds
that release the DS2775–DS2778 from a protection
state. Figure 3 shows Li+ protection circuitry example
waveforms.
Overvoltage (OV)
If either of the voltages on (V
IN2
- V
IN1
) or (V
IN1
- V
SS
)
exceeds the overvoltage threshold, V
OV
, for a period
longer than overvoltage delay, t
OVD
, the CC pin is dri-
ven low to shut off the external charge FET. The DC out-
put remains high during overvoltage to allow
discharging. When (V
IN2
- V
IN1
) and (V
IN1
- V
SS
) falls
below the charge-enable threshold, V
CE
, the
DS2775–DS2778 turn the charge FET on by driving CC
high. The DS2775–DS2778 drive CC high before
[(V
IN2
-V
IN1
) and (V
IN1
- V
SS
)] < V
CE
if a discharge
condition persists with V
SNS
≥ 1.2mV and [(V
IN2
- V
IN1
)
and (V
IN1
- V
SS
)] < V
OV
.
ACTIVE
PMOD = 0
UVEN = 0
SLEEP
PSPIO = 0
PSDQ = 0
RISING EDGE ON DQ
CHARGER DETECT
PULL DQ LOW
CHARGER DETECT
ACTIVE
PMOD = 0
UVEN = 1
SLEEP
PSPIO = 0
PSDQ = 1
V
IN1
OR V
IN2
< V
UV
PULL PIO LOW
RISING EDGE ON DQ
CHARGER DETECT
ACTIVE
PMOD = 1
UVEN = 0
SLEEP
PSPIO = 1
PSDQ = 0
PULL DQ LOW FOR t
SLEEP
PULL DQ LOW FOR t
SLEEP
PULL DQ LOW
PULL PIO LOW
CHARGER DETECT
ACTIVE
PMOD = 1
UVEN = 1
SLEEP
PSPIO = 1
PSDQ = 1
V
IN1
OR V
IN2
< V
UV
Figure 1. Sleep-Mode State Diagram for DS2775/DS2776
ACTIVE
PMOD = 0
UVEN = 0
SLEEP
PSPIO = 0
PSDQ = X
RISING EDGE ON SDA OR SCL
CHARGER DETECT
V
IN1
OR V
IN2
< V
UV
CHARGER DETECT
ACTIVE
PMOD = 0
UVEN = 1
SLEEP
PSPIO = 0
PSDQ = X
RISING EDGE ON SDA OR SCL
PULL PIO LOW
CHARGER DETECT
PULL SDA AND SCL LOW
FOR t
SLEEP
ACTIVE
PMOD = 1
UVEN = 0
SLEEP
PSPIO = 1
PSDQ = X
RISING EDGE ON SDA OR SCL
PULL SDA AND SCL LOW
FOR t
SLEEP
PULL PIO LOW
CHARGER DETECT
V
IN1
OR V
IN2
< V
UV
ACTIVE
PMOD = 1
UVEN = 1
SLEEP
PSPIO = 1
PSDQ = X
RISING EDGE ON SDA OR SCL
Figure 2. Sleep-Mode State Diagram for DS2777/DS2778