Datasheet

I
MAX
I
MIN
Trickle
V
LBAT
V
MCV
Current
Voltage
Time
Phase1 Phase2
FastCharge
Voltage
Current
Charge
Qualification
bq2000T
www.ti.com SLUS149D –MAY 1999–REVISED JANUARY 2010
Lithium-Ion Batteries
The bq2000T uses a two-phase fast-charge algorithm for Li-Ion batteries (Figure 4). In phase one, the bq2000T
regulates constant current until V
BAT
rises to V
MCV
. Once V
BAT
= V
MCV
, the device identifies the cell as a Li-ion,
and changes the termination method from ΔT/Δt to minimum current. The bq2000T then moves to phase two,
regulates the battery with constant voltage of V
MCV
, and terminates when the charging current falls below the I
MIN
threshold or the timer expires (whichever happens first). A new charge cycle is started if the cell voltage falls
below the V
RCH
threshold.
Figure 4. Lithium-Ion Charge Algorithm
During the current-regulation phase, the bq2000T monitors charge time, battery temperature, and battery voltage
for adherence to the termination criteria. During the final constant-voltage stage, in addition to the charge time
and temperature, it monitors the charge current as a termination criterion. There is no post-charge maintenance
mode for Li-Ion batteries.
Table 1 summarizes the charging process for both Nickel and Li-Ion batteries.
Table 1. Charge Algorithm
BATTERY CHEMISTRY CHARGE ALGORITHM
1. Charge qualification
2. Trickle charge, if required
3. Fast charge (constant current)
NiCd or NiMH
(V
BAT
< V
MCV
always)
4. Fast charge termination (rate of temperature rise, maximum charge time = 1 MTO)
5. Top-off (optional)
6. Trickle charge
1. Charge qualification
2. Trickle charge, if required
Li-Ion
3. Fast charge (constant current)
(V
BAT
≤ V
MCV
)
4. Fast charge (constant voltage)
5. Charge termination (minimum current, maximum charge time = 2 MTO)
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