DS2780 Standalone Fuel Gauge IC

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fuel gauge data to EEPROM, but some data loss can occur depending on the timing of the protection event and the

backup. When the protection circuit is connected directly to the battery the protection is absolute, no charging will

occur during a protection event. With the protection circuit located outside, see Figure 3, the DS2780 will remain

powered up during a protection event.

The disadvantage to this configuration is that you run the risk of

Communication to the DS2780 is broken during a protection event regardless of protector location.

POWER MODES

The DS2780 has two power modes: ACTIVE and SLEEP. On initial power up, the DS2780 defaults to ACTIVE

mode. While in ACTIVE mode, the DS2780 is fully functional with measurements and capacity estimation

continuously updated. In SLEEP mode, the DS2780 conserves power by disabling measurement and capacity

estimation functions, but preserves register contents. SLEEP mode is entered under two different conditions and

an enable bit for each condition makes entry into SLEEP optional. SLEEP mode can be enabled using the Power

Mode (PMOD) bit or the Under Voltage Enable (UVEN) bit.

current will flow. A PMOD SLEEP condition transitions back to ACTIVE mode when DQ is pulled high.

The second option for entering SLEEP is an under voltage condition. When the UVEN bit is set, the DS2780

resumes.

NOTE: PMOD and UVEN SLEEP features must be disabled when a battery is charged on an external charger that

does not connect to the DQ pin. PMOD SLEEP can be used if the charger pulls DQ high. UVEN SLEEP can be

used if the charger toggles DQ. The DS2780 remains in SLEEP on a charger that fails to properly drive DQ and

therefore does not measure or accumulate current when a battery is charged.

INITIATING COMMUNICATION IN SLEEP

When beginning communication with a DS2780 in PMOD SLEEP, DQ must be pulled up first and then a 1-Wire

Reset pulse must be issued by the master. In UVEN SLEEP, the procedure depends on the state of DQ when

UVEN SLEEP was entered. If DQ was low, DQ must be pulled up and then a 1-Wire Reset pulse must be issued

by the master as with PMOD SLEEP. If DQ was high when UVEN SLEEP was entered, then the DS2780 is

prepared to receive a 1-Wire reset from the master. In the first two cases with DQ low during SLEEP, the DS2780

does not respond

to the first rising edge of DQ with a presence pulse.

VOLTAGE MEASUREMENT

Battery voltage is measured at the VIN input with respect to VSS. It has a range of 0V to 4.992V (pin voltage

limited to 4.5V) and a resolution of 4.88mV. The measurement is stored in the VOLTAGE register in two’s

compliment form and is updated every 440ms. 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 4.

Figure 4. Voltage Register Format

VOLT

Read Only

MSB—Address 0Ch

LSB—Address 0Dh

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: 4.88mV