Datasheet

the allowed limits. If the voltage is too high, the chip
goes to the battery absent state and waits until a new
charge cycle is started.
Fast charge continues until termination by one or more
of the five possible termination conditions:
n
Delta temperature/delta time (∆T/∆t)
n Negative delta voltage (-
∆
V)
n
Maximum voltage
n
Maximum temperature
n
Maximum time
-∆V Termination
If the DVEN input is high, the bq2003 samples the volt
-
age at the BAT pin once every 34s. If V
CELL
is lower
than any previously measured value by 12mV ±4mV,
fast charge is terminated. The -∆V test is valid in the
range V
MCV
- (0.2 ∗ V
CC
)<V
CELL
<V
MCV
.
Voltage Sampling
Each sample is an average of 16 voltage measurements
taken 57µs apart. The resulting sample period (18.18ms)
filters out harmonics around 55Hz. This technique mini
-
mizes the effect of any AC line ripple that may feed
through the power supply from either 50Hz or 60Hz AC
sources. Tolerance on all timing is ±16%.
Voltage Termination Hold-off
A hold-off period occurs at the start of fast charging.
During the hold-off period, -∆V termination is disabled.
This avoids premature termination on the voltage spikes
sometimes produced by older batteries when fast-charge
current is first applied. ∆T/∆t, maximum voltage and
maximum temperature terminations are not affected by
the hold-off period.
∆T/∆t Termination
The bq2003 samples at the voltage at the TS pin every
34s, and compares it to the value measured two samples
earlier. If V
TEMP
has fallen 16mV ±4mV or more, fast
charge is terminated. The ∆T/∆t termination test is
valid only when V
TCO
<V
TEMP
<V
LTF
.
Temperature Sampling
Each sample is an average of 16 voltage measurements
taken 57µs apart. The resulting sample period
(18.18ms) filters out harmonics around 55Hz. This tech
-
nique minimizes the effect of any AC line ripple that
may feed through the power supply from either 50Hz or
60Hz AC sources. Tolerance on all timing is ±16%.
Maximum Voltage, Temperature, and Time
Anytime V
CELL
rises above V
MCV,
CHG goes high (the LED
goes off) immediately. If the bq2003 is not in the voltage
hold-off period, fast charging ceases if V
CELL
remains above
MCV for a minimum of t
MCV
.IfV
CELL
then falls back be
-
low V
MCV
before 1.5t
MCV
±50ms, the chip transitions to the
Charge Complete state (maximum voltage termination). If
V
CELL
remains above V
MCV
beyond 1.5t
MCV
, the bq2003
transitions to the Battery Absent state (battery removal).
See Figure 3.
If the bq2003 is in the voltage hold-off period when
V
CELL
rises above V
MCV,
the LED goes out but fast
charging continues until the expiration of the hold-off
period. Temperature sampling continues during the
hold-off period as well. If a new battery is inserted be
-
fore the hold-off period expires, it continues in the fast
charge cycle started by its predecessor. No precharge
qualification is performed, and a temperature sample
5
bq2003
Corresponding
Fast-Charge Rate TM1 TM2
Typical Fast Charge
and Top-Off
Time Limits
Typical -
∆
V/MCV
Hold-Off
Time (seconds)
Top-Off
Rate
C/4 Low Low 360 137 Disabled
C/2 Float Low 180 820 Disabled
1C High Low 90 410 Disabled
2C Low Float 45 200 Disabled
4C Float Float 23 100 Disabled
C/2 High Float 180 820 C/16
1C Low High 90 410 C/8
2C Float High 45 200 C/4
4C High High 23 100 C/2
Note: Typical conditions = 25°C, V
CC
= 5.0V.
Table 2. Fast-Charge Safety Time/Hold-Off/Top-Off Table