Datasheet

bq2000
www.ti.com SLUS138D –JANUARY 2008–REVISED DECEMBER 2009
Table 5. Summary of Li-Ion Charging Characteristics
PARAMETER VALUE
(1)
Maximum cell voltage (V
MCV
) 2 V
Minimum pre-charge qualification voltage (V
LBAT
) 950 mV
High-temperature cutoff voltage (V
TCO
) 0.225 × V
CC
High-temperature fault voltage (V
HTF
) 0.25 × V
CC
Low-temperature fault voltage (V
LTF
) 0.5 × V
CC
2 × R
MTO
× C
MTO
× 35,988
bq2000 fast-charge maximum time out (MTO)
(See Maximum Charge Time section for full explanation)
Fast-charge charging current (I
MAX
) 0.05/R
SNS
Hold-off period MTO/32
Minimum current (for fast-charge termination) I
MAX
/7
Trickle-charge frequency (before fast charge only) 1Hz
Trickle-charge pulse-width (before fast charge only) See Figure 8
(1) See the DC Thresholds Specification for details.
Charge Status Display
The charge status is indicated by open-drain output LED. Table 6 summarizes the display output of the bq2000.
A temperature fault or timer expiring changes the charge state immediately (according to Figure 2) and will thus
change the LED status immediately and accordingly.
Table 6. Charge Status Display
bq2000 CHARGE STATE LED STATUS
Charge qualification (including battery conditioning and charge suspended) 1 Hz flash
Fast charge (current and voltage regulation) Low
Top-off charge
Trickle maintenance charge (after fast charge)
Charge complete High impedance
Battery absent
Sleep mode
Sleep Mode
The bq2000 features a sleep mode for low power consumption. This mode is enabled when the voltage at the
BAT pin is above the low-power-mode threshold, V
SLP
. During sleep mode, the bq2000 shuts down all
unnecessary internal circuits, drives the LED output to high-impedance state, and drives the MOD pin low.
Restoring BAT below the V
MCV
threshold initiates the IC and starts a fast-charge cycle. Normally, the bq2000
only enters sleep mode when there is no battery connected on the output and the charger is idling with nothing to
charge. In addition, V
IN
needs to be high enough such that when V
IN
is present on the output, V
BAT
would be
greater than V
SLP
. In sleep mode, the output voltage will decay to V
MCV
at which point the bq2000 turns on and
pulses the MOD pin several times. With no battery connected, the output will rise to near V
IN
at which point the
bq2000 re-enters sleep mode. During sleep mode, the RC pin will be at V
SS
potential. A typical sleep mode
waveform is shown in Figure 18.
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