BQ2002C_11 Datasheet, PDF (4/17 Pages) Texas Instruments – NiCd/NiMH Fast-Charge Management IC

bq2002C
VCC = 0
Fast Charging
Pulse-Trickle
Fast Charging
CC Output
1s
LED
See
Table 1
Charge initiated by application of power
Charge initiated by battery replacement
TD2002C1.eps
Figure 4. Charge Cycle Phases
Starting A Charge Cycle
Either of two events starts a charge cycle (see Figure 4):
1. Application of power to VCC or
2. Voltage at the BAT pin falling through the maximum
cell voltage VMCV where
VMCV = 2V ±5%.
If the battery is within the configured temperature and
voltage limits, the IC begins fast charge. The valid
battery voltage range is VLBAT < VBAT < VMCV, where
VLBAT = 0.175 ∗ VCC ±20%
The valid temperature range is VTS > VHTF where
VHTF = 0.6 ∗ VCC ±5%.
If VBAT ≤ VLBAT or VTS ≤ VHTF, the IC enters the charge-
pending state. In this state pulse trickle charge is
applied to the battery and the LED flashes until the
voltage and temperature come into the allowed fast
charge range or VBAT rises above VMCV. Anytime VBAT
≥ VMCV, the IC enters the Charge Complete/Battery
Absent state. In this state the LED is off and trickle
charge is applied to the battery until the next new
charge cycle begins.
Fast charge continues until termination by one or more of
the five possible termination conditions:
n Peak voltage detection (PVD)
n Negative delta voltage (-∆V)
n Maximum voltage
n Maximum temperature
n Maximum time
Table 1. Fast-Charge Safety Time/Hold-Off Table
Typical
Fast-
Typical PVD
Corresponding
Charge
and -∆V
Fast-Charge
Time Limits
Hold-Off
Rate
TM Termination (minutes) Time (seconds)
Pulse-
Trickle
Rate
Pulse-
Trickle
Pulse Width
(ms)
Maximum
Synchronized
Sampling
Period
(seconds)
C/2
Mid
PVD
160
300
C/32
73
18.7
1C
Low
PVD
80
150
C/32
37
18.7
2C
High
-∆V
40
75
C/32
18
9.4
Notes:
Typical conditions = 25°C, VCC = 5.0V
Mid = 0.5 _* VCC ±0.5V
Tolerance on all timing is ±12%.
4