BQ2003 Datasheet, PDF (5/15 Pages) Texas Instruments – Fast-Charge IC

bq2003
Table 2. Fast-Charge Safety Time/Hold-Off/Top-Off Table
Corresponding
Fast-Charge Rate
C/4
C/2
1C
2C
4C
C/2
1C
2C
4C
TM1
Low
Float
High
Low
Float
High
Low
Float
High
TM2
Low
Low
Low
Float
Float
Float
High
High
High
Typical Fast Charge
and Top-Off
Time Limits
360
180
90
45
23
180
90
45
23
Typical -∆V/MCV
Hold-Off
Time (seconds)
137
820
410
200
100
820
410
200
100
Top-Off
Rate
Disabled
Disabled
Disabled
Disabled
Disabled
C/16
C/8
C/4
C/2
Note:
Typical conditions = 25°C, VCC = 5.0V.
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)
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 VTEMP has fallen 16mV ±4mV or more, fast
charge is terminated. The ∆T/∆t termination test is
valid only when VTCO < VTEMP < VLTF.
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 VCELL is lower
than any previously measured value by 12mV ±4mV,
fast charge is terminated. The -∆V test is valid in the
range VMCV - (0.2 ∗ VCC) < VCELL < VMCV.
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
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 VCELL rises above VMCV, CHG goes high (the LED
goes off) immediately. If the bq2003 is not in the voltage
hold-off period, fast charging ceases if VCELL remains above
MCV for a minimum of tMCV. If VCELL then falls back be-
low VMCV before 1.5tMCV ±50ms, the chip transitions to the
Charge Complete state (maximum voltage termination). If
VCELL remains above VMCV beyond 1.5tMCV, the bq2003
transitions to the Battery Absent state (battery removal).
See Figure 3.
If the bq2003 is in the voltage hold-off period when
VCELL rises above VMCV, 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