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LTC1760

1760fa

0000b: Clears CALIBRATE_BAT1 and CALIBRATE_BAT2

and allows LTC1760 to chose. Power on reset default.

May not be updated if a calibration is in progress.

Option 2) SMBus Host allows LTC1760 to choose battery

to be calibrated.

BatterySystemStateCont(CALIBRATE_BAT[4:1]) = 0000b.

See previous option.

The LTC1760 determines that the battery requires

calibration by reading BatteryMode(CONDITION_FLAG).

This flag is cached in the LTC1760. The LTC1760 sets

BatterySystemStateCont(CALIBRATE_REQUEST) high.

The LTC1760 will always select the battery that is requesting

calibration. If both batteries are requesting calibration, the

LTC1760 will select Battery 1. If neither battery is request-

ing calibration, then calibration cannot occur.

5.2 Initiating Calibration of Selected Battery

The SMBus Host initiates a calibration by writing to

BatterySystemStateCont(CALIBRATE). Follow rules of the

previous section to preserve battery intended for calibra-

tion. The SMBus Host must only set the calibration bit

once per calibration.

The LTC1760 will discharge the selected battery as long as

the calibration is in progress (CALIBRATE high). Updates

to the cached BatteryMode(CONDITION_FLAG) will be

inhibited while CALIBRATE is asserted. This means that

discharge of the battery will continue even if the battery

clears the CONDITION_FLAG.

5.3 Terminating Calibration of Selected Battery

Calibration will end when CALIBRATE is cleared. CALI-

BRATE will be cleared when:

• AC is removed.

• The battery being calibrated is removed. When the

battery being calibrated is removed, the LTC1760

will automatically calibrate the other battery if it is

requesting calibration.

• BatterySystemStateCont(POWER_NOT_GOOD) is high.

Summary of SDA, SCL and SMBALERT Operation as a Function

of MODE and VDDS Levels

CONDITION

LTC1760 OPERATING MODE

VMODE = GND

VVDDS < VIL_VDDS

SCL: Clock for Status Indicators

SDA: Battery 2 Status

SMBALERT: Battery 1 Status

VMODE = GND

VVDDS > VIH_VDDS

SCL, SDA, SMBALERT: Normal Operation

LTC1760 Charging Inhibited

VMODE = VVCC2

VVDDS < VIL_VDDS

SCL, SDA Ignored and May Float Low

SMBALERT: Normal Operation

SCL1, SDA1, SCL2 and SDA2: Normal Operation and

Charging is Allowed

VMODE = VVCC2

VVDDS > VIH_VDDS

Normal Operation on all Pins, Charging is Allowed

• The battery sets Alarm Warning

(TERMINATE_DISCHARGE) high.

• The battery sets Alarm Warning

(FULLY_DISCHARGED) high.

• A zero is written to the CALIBRATE bit.

The LTC1760 will attempt to initiate a charge cycle after

the discharge cycle is completed.

6 MODE Pin Operation

TheMODEpinisamultifunctionpinthatallowstheLTC1760

to: 1) display charging status in stand alone operation;

2) activate hardware charge inhibit; 3) charge when SCL

and SDA are low and; 4) charge with an SMBus Host.

OPERATION

6.1 Standalone Charge Indication

When MODE is tied to GND and VVDDS < VIL_VDDS, the

function of SDA, SMBALERT, and SCL are changed as

described below:

SDA is an output and is used to monitor charging status

of Battery 2. Allowed values are:

Low: Battery 2 is charging.

High: Battery 2 not charging (AC is not present or bat-

tery is not present).

Blinking: Battery 2 charge complete (AC is present,

battery is present and not charging).

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