Rainbow-electronics DS2778 Manual do Utilizador descarregar pdf (Página 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

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

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

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

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

MSb LSb MSb LSb

“S”: SIGN BIT(S)

UNITS: 1.5625μV/R

SNS

Figure 7. Average Current Register Format

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 44 45

DS2775/DS2776/DS2777/DS2778 1

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