DS2780 Maxim Integrated Products, DS2780 Datasheet - Page 7

• Manufacturer Part Number: DS2780
• Description: Stand-Alone Fuel Gauge IC
• Manufacturer: Maxim Integrated Products

www.DataSheet4U.com
VOLTAGE MEASUREMENT
Battery voltage is measured at the VIN input with respect to VSS over a range of 0V to 4.992V, with a resolution of
4.88mV. The result is updated every 440ms and placed in the VOLTAGE register in two’s compliment form.
Voltages above the maximum register value are reported at the maximum value; voltages below the minimum
register value are reported at the minimum value. The format of the voltage register is shown in Figure 3.
Figure 3. Voltage Register Format
VIN is usually connected to the positive terminal of a single cell Lithium-Ion battery via a 1kW resistor. The input
impedance is sufficiently large (15MW) to be connected to a high impedance voltage divider in order to support
multiple cell applications. The pack voltage should be divided by the number of series cells to present a single cell
average voltage to the VIN input. In Figure 2, the value of R can be up to 1MW without incurring significant error
due to input loading.
TEMPERATURE MEASUREMENT
The DS2780 uses 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. The format of the temperature register is shown in Figure 4.
Figure 4. Temperature Register Format
CURRENT MEASUREMENT
In the ACTIVE mode of operation, the DS2780 continually measures the current flow into and out of the battery by
measuring the voltage drop across a low-value current-sense resistor, R
SNS and VSS is ±51.2mV. The input linearly converts peak signal amplitudes 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 differentially at 18.6kHz and updates the Current register at the completion of each conversion cycle.
The Current register is updated every 3.515s with the current conversion result in two’s complement form. Charge
currents above the maximum register value are reported at the maximum value (7FFFh = +51.2mV). Discharge
currents below the minimum register value are reported at the minimum value (8000h = -51.2mV).
VOLT
MSb
“S”: sign bit(s), “X”: reserved
TEMP
MSb
“S”: sign bit(s), “X”: reserved
S
S
2
2
9
9
MSB—Address 0Ch
MSB—Address 0Ah
2
2
8
8
2
2
7
7
2
2
6
6
2
2
5
5
2
2
4
4
LSb
LSb
2
2
3
3
7 of 27
MSb
MSb
2
2
2
2
2
2
1
1
LSB—Address 0Dh
LSB—Address 0Bh
2
2
SNS
0
0
. The voltage-sense range between
DS2780 Stand-Alone Fuel Gauge IC
X
X
X
X
X
X
Units: 0.125°C
Units: 4.88mV
Read Only
Read Only
X
X
LSb
LSb
X
X