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PS200-I/P

PowerSmart® Configurable Battery Charger

Microchip Technology 

2.2 Lithium Charging

To ensure the proper treatment of lithium chemistries

during extreme temperature and voltage conditions,

multi-step charging is required. The PS200 measures

key voltage, temperature and time parameters. It com-

pares them to user defined voltage, temperature and

time limits. These limits are described in Section 2.4

“Lithium Configurable Parameters”.

Note: Refer to Figure 2-1 and Figure 2-2 for

clarification when reading this section.

2.2.1

CHARGE PENDING STATE –

BEGINNING THE CHARGE CYCLE

The PS200 is initially set in the Charge Pending state

(A). In this state, the presence of a battery pack must

be sensed in order to begin the charging cycle. The

PS200 comes up in the Charge Pending state, after a

Reset, independent of the previous state.

2.2.2 CHARGE QUALIFICATION STATE

During charge qualification, the battery’s temperature

and voltage are measured to determine the next

charging state. There are four possible next states (see

Figure 2-1).

1. If the battery’s temperature is outside of the

limits for charge initiation (TMAX, TMIN) then the

next state is Charge Suspend (C).

2. If the battery’s voltage is less than the minimum

voltage for charge initiation (VMIN) and its

temperature is within the limits for charge

initiation (TMAX, TMIN), then the next state is

Precharge (D).

3. If the battery’s voltage is above the minimum

voltage for charge initiation (VMIN) and its tem-

perature is within the limits for charge initiation

(TMAX, TMIN), then the next state is Current

Regulation (E).

4. If the battery’s voltage is above the voltage at

which charging will restart (VRCHG), then the

next state is Charge Complete (G).

PS200

2.2.3 PRECHARGE STATE

The Precharge state allows for the recovery of a deeply

discharged battery pack by applying a low charge rate.

In this state, a user configured precharge current is

applied to the battery, resulting in an increase in the

battery’s voltage (refer to Figure 2-2). There are three

possible next states (see Figure 2-1).

1. If the battery’s voltage is above the minimum

voltage for charge initiation (VMIN) and the

battery’s temperature is within the limits for

charge initiation (TMAX, TMIN), then the next state

is Current Regulation (E).

2. If the Precharge state time limit is exceeded (tp)

and the battery’s voltage remains less than the

minimum voltage for charge initiation (VMIN),

then the next state is Charge Suspend (C).

If the Precharge state time limit is exceeded (tp)

and the battery’s temperature is greater than the

maximum temperature for charge initiation (TMAX),

then the next state is Charge Suspend (C).

If the Precharge state time limit is exceeded (tp)

and the battery’s temperature is less than the

minimum temperature for charge initiation (TMIN),

then the next state is Charge Suspend (C).

3. If the battery pack is taken away (BATPRES = 0),

then the PS200 enters the Charge Pending (A)

state.

2.2.4 CHARGE SUSPEND STATE

In the Charge Suspend state, no current is applied to

the battery pack. There are two possible next states

(see Figure 2-1).

1. If the battery’s temperature is within the limits for

charge initiation (TMAX, TMIN) and its voltage is

less than the voltage at which charging would

restart (VRCHG), then the next state is Precharge

(D).

2. If the battery pack is taken away (BATPRES = 0),

then the PS200 enters the Charge Pending (A)

state.

© 2005 Microchip Technology Inc.

DS21891B-page 7

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