BQ2000T_15 Datasheet, PDF (7/29 Pages) Texas Instruments – Programmable Multi-Chemistry Fast-Charge Management IC

bq2000T
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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.
I_MAX
Voltage
V_MCV
Trickle
I_MIN
Fast Charge
Phase 1
Phase 2
Current
V_LBAT
Time
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.
BATTERY CHEMISTRY
NiCd or NiMH
(V_BAT < V_MCV always)
Li-Ion
(V_BAT ≤ V_MCV )
Table 1. Charge Algorithm
CHARGE ALGORITHM
1. Charge qualification
2. Trickle charge, if required
3. Fast charge (constant current)
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
3. Fast charge (constant current)
4. Fast charge (constant voltage)
5. Charge termination (minimum current, maximum charge time = 2 MTO)
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