PS810 datasheet(10/46 Pages) MICROCHIP

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PS810

DS21904C-page 10

3.2

Operational Modes

The PS810 operates on a continuous cycle, measuring

current, voltage and temperature, then performing fuel

gauge calculations. There are four power modes: Run

mode, in which the measuring and calculating loop

constantly repeats; Bus Inactive Low-Power mode, in

which only self-discharge is calculated; Low-Voltage

Sleep mode, in which there are no measurements and

only wake-up circuitry is powered; and Shelf-Sleep

mode, in which only communication line sensors are

powered.

3.2.1

RUN MODE

Run mode is the highest power consuming mode.

During Run mode, all measurements and calculations

occur. Current, voltage and temperature measure-

ments are each made sequentially. Run mode is active

until voltage drops below the Sleep voltage, the bus

goes inactive or the Shelf-Sleep command is executed.

3.2.2

BUS INACTIVE LOW-POWER MODE

The PS810 enters Low-Power mode when all of the

following conditions are true:

• Current is zero (optional)

• The communication pins are low for at least

8 periods of 512 ms each

• There is no communication attempt for at least

8 periods of 512 ms each

To enter this mode, typically, there must be no load or

charger present and no communication host. The pack

is out of the system. In this mode, the PS810 will draw

less current from the battery, approximately 25

μA and

will only track self-discharge. Alternatively, if self-

discharge tracking is not required, Ultra Low-Power

mode can be used and the PS810 will draw less than

1 microamp.

3.2.3

LOW-VOLTAGE SLEEP MODE

Entry to Low-Voltage Sleep mode can only occur when

the measured pack voltage at VC1 input is below a

preset limit set by the parameter SleepVoltage (in mV)

and the current is zero (less than NullCurr). Sleep

mode may be exited to Run mode when the voltage at

VC1 is greater than the wake-up voltage, which is

3.2 volts, 10%.

While in 10% Sleep mode, no measurements occur

and no calculations are made. The fuel gauge display

is not operational, no communications are recognized

and only a wake-up condition will permit an exit from

Sleep mode. Sleep mode is one of the lowest power

consuming modes and is used to conserve battery

energy following a complete discharge.

There are two power levels that can be chosen for Low-

Voltage

Sleep

mode.

Low-Power

mode

draws

approximately 20

μA and will wake-up automatically

when the voltage rises above the wake-up voltage,

which is a constant 3.2 volts above the wake-up volts,

+/-5%. Ultra Low-Power mode draws less than 1

μA

and requires an external source to drive the communi-

cation line high to wake-up, since the voltage wake-up

comparator is powered down.

3.2.4

SHELF-SLEEP MODE

Shelf-Sleep mode can be entered by a battery data

command on the communication bus for conserving

energy while shipping battery packs. It can be exited

only by an external source driving the communication

data line high. This mode uses the Ultra Low-Power

Sleep mode, resulting in current draw less than

1 microamp. This mode is entered by writing a pass-

word to SMBus command code, 0x43. A word write

protocol is used to write the password, 0x5A7A.

TABLE 3-2:

OPERATIONAL MODES

Mode

Entry

Exit

Notes

Run

Voltage > Wake-up voltage

or data line driven high

Voltage less than SleepVoltage, bus Idle or

Shelf-Sleep command issued

Highest power

consumption and

accuracy.

Bus Inactive

Low-Power

Current < NullCurr,

communication lines low

and no communication

attempts

Activity on communication lines

Only self-discharge

calculated.

Low-Voltage

Sleep

VC(1) < SleepVoltage,

Current is not zero

Voltage > Wake-up voltage (Low-Power mode),

Data line driven high (Ultra Low-Power mode)

No measurements

made.

Shelf-Sleep

Can be entered by SMBus

command

Data line driven high

No measurements

made.

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