PS810 datasheet(19/46 Pages) MICROCHIP

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DS21904C-page 19

PS810

5.0

CHARGE CONTROL

5.1

Full Charge Detection Methods

For a typical lithium ion constant-current/constant-

voltage charge system, the PS810 will monitor the taper

current that enters the battery. Once the battery has

reached the final voltage level of the charger, when VC1

is greater than EOCVolt, taper monitoring will begin.

Once the taper current falls between TaperCRate and

TaperLow, indicating that the battery is full, the End-Of-

Charge (EOC) will be triggered. For pulse charging, the

average current will be monitored. When average current

falls below EOCCurAvg, the EOC will be triggered. So

that a sudden drop or removal of charge current doesn’t

trigger a false EOC when using taper current, the current

and the average current must be within StableCurr of

each other.

Thus, the conditions to trigger EOC are:

Cell Voltage > EOCVolt and

TaperCRate > Current > TaperLow and

Average Current – Current < StableCurr

For pulse charging, replace condition 2 with Average

Current < EOCCurAvg and remove condition 3.

When a valid, fully charged EOC condition is detected,

the following actions occur:

• The FULLY_CHARGED status bit in BatteryStatus

is set to ‘1’ to indicate a full condition. (This will

remain set until RelativeStateOfCharge drops

below the ClrFullyChrg value in memory.)

• Remaining capacity is set to FCC and thus,

RelativeStateOfCharge is set to 100%.

5.2

Temperature Algorithms

The PS810 provides a temperature alarm set point.

HighTempAl: When the measured temperature is

greater than HighTempAl, the OVER_TEMP_ALARM

bit is set.

TABLE 5-1:

CHARGE CONTROL PARAMETERS

Parameter

Name

Bytes

Units

Typical

Value

Operational Description

HighTempAl

(°Celsius *

10 + 200)/4

200

OVER_TEMP_ALARM threshold bit in AlarmWarning register, coded

value = (°Celsius * 10 + 200)/4. When the temperature exceeds

HighTempAl, the OVER_TEMP_ALARM becomes active.

EOCCurAvg

200

EOC trigger for pulse charging. If the average current during pulse

charging has dropped below the EOCCurAvg threshold for a pass

count equal to the parameter value, EOCRecheck, the End-Of-Charge

state will be reached.

EOCRecheck

integer

Number of checks before EOC trigger. The End-Of-Charge conditions

must remain for at least this number of periods, before being

considered true, to help filter out false full conditions due to spikes.

EOCVolt

4150

EOC trigger cell voltage. When a cell reaches this voltage, the

End-Of-Charge determination will start monitoring the current to

determine when the battery is full. When the current is in the proper

range and the cell voltage is greater than EOCVolt, then

FULLY_CHARGED bit in BatteryStatus will be set.

StableCurr

EOC trigger current deviation level. In order to prevent current spikes

from causing a premature taper current trigger, the average current and

the instantaneous current must be within StableCurr of each other.

TaperCRate

1/64 C

Upper limit EOC taper current based on temperature, 64 = 1C.

TaperLow

1/64 C

Lower limit EOC taper current, 64 = 1C.

ConfigEOCD

bitmap

10011111 Bit coded as follows:

Bit

Function

Limit remcap to FCC

6Unused

Trigger EOC on average current

Trigger EOC on taper current

Disallow multiple EODs

Limit capacity to EODCap until EOD

Set capacity to residual capacity at VEOD

Learn FCC at VEOD

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