Temperature measurement, Current measurement – Rainbow Electronics DS2778 User Manual
Page 14
Temperature Measurement
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.
Current Measurement
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
SNS
. The voltage-sense range between SNS
and V
SS
is ±51.2mV with a least significant bit (LSb) of
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.
DS2775/DS2776/DS2777/DS2778
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
14
______________________________________________________________________________________
MSB—ADDRESS 0Ah
LSB—ADDRESS 0Bh
S 2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
X X X X X
MSb
LSb
MSb
LSb
“S”: SIGN BIT(S), “X”: RESERVED
UNITS: 0.125°C
Figure 5. Temperature Register Format
MSB—ADDRESS 0Eh
LSB—ADDRESS 0Fh
S 2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
MSb
LSb
MSb
LSb
“S”: SIGN BIT(S)
UNITS: 1.5625μV/R
SNS
Figure 6. Current Register Format
MSB—ADDRESS 08h
LSB—ADDRESS 09h
S 2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
MSb
LSb
MSb
LSb
“S”: SIGN BIT(S)
UNITS: 1.5625μV/R
SNS
Figure 7. Average Current Register Format