DS2777 MAXIM [Maxim Integrated Products], DS2777 Datasheet - Page 14

• Manufacturer Part Number: DS2777
• Description: 2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with Protector and Optional SHA-1 Authentication
• Manufacturer: MAXIM [Maxim Integrated Products]

2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
The DS2775–DS2778 use an integrated temperature
sensor to measure battery temperature with a resolution
of 0.125°C. Temperature measurements are updated
every 440ms and placed in the Temperature register in
two’s complement form.
In active mode, the DS2775–DS2778 continuously mea-
sure the current flow into and out of the battery by mea-
suring the voltage drop across a low-value current-sense
resistor, R
and V
Figure 5. Temperature Register Format
Figure 6. Current Register Format
Figure 7. Average Current Register Format
14
“S”: SIGN BIT(S)
MSb
“S”: SIGN BIT(S), “X”: RESERVED
MSb
“S”: SIGN BIT(S)
MSb
______________________________________________________________________________________
SS
S
S
S
is ±51.2mV with a least significant byte (LSB) of
SNS
2
2
2
Temperature Measurement
14
14
9
. The voltage-sense range between SNS
2
2
2
13
MSB—ADDRESS 0Ah
MSB—ADDRESS 0Eh
13
8
MSB—ADDRESS 08h
Current Measurement
2
2
2
12
7
12
2
2
2
11
6
11
2
2
2
10
5
10
2
2
2
4
9
9
LSb
LSb
2
2
LSb
2
3
8
8
1.5625µV. The input linearly converts peak signal ampli-
tudes up to 102.4mV as long as the continuous signal
level (average over the conversion cycle period) does
not exceed ±51.2mV. The ADC samples the input differ-
entially at 18.6kHz and updates the Current register at
the completion of each conversion cycle (3.52s). Charge
currents above the maximum register value are reported
as 7FFFh. Discharge currents below the minimum regis-
ter value are reported as 8000h.
The Average Current register reports an average cur-
rent level over the preceding 28.16s. The register value
is updated every 28.16s in two’s complement form and
represents an average of the eight preceding Current
register values.
MSb
UNITS: 0.125°C
MSb
UNITS: 1.5625μV/R
UNITS: 1.5625μV/R
MSb
2
2
2
2
7
7
2
2
2
1
6
6
2
2
2
LSB—ADDRESS 0Bh
0
5
LSB—ADDRESS 0Fh
LSB—ADDRESS 09h
5
SNS
SNS
2
X
2
4
4
2
2
X
3
3
2
2
X
2
2
2
2
X
1
1
LSb
LSb
LSb
2
2
X
0
0