BQ2000_15 Datasheet, PDF (10/29 Pages) Texas Instruments – Programmable Multi-Chemistry Fast-Charge Management IC

bq2000
SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009
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DC+
D3
MMSD914LT
D4
S1A
C6
47 mF
Q1
FMMT718
Q2
MMBT3904LT1
L1
47 mH
D2
ZHCS1000
R10
1 KW
D5
MMSD914LT
C9
R12
120 OHMS
1000 PF
VCC
D6
BZT52-C5V1
R2
2 KW
C3
10 mF
D1
RED
C2
0.1
C7
C4
4.7 PF
0.0022 mF
R1
C8
0.33 mF
R4
12.4K
U1
1
2
3
4
SNS
VSS
LED
BAT
100 KW
MOD
VCC
RC
8
7
6
5
TS
bq2000
C1
0.1
R8
6.81 KW
R5
20 KW
Q3
MMBT3904LT1
R11
220 W
R6
210 KW
BAT+
C5
10 mF
THERM
R9
221 KW
CHEMISTRY
R7
200 KW
BAT-
R13
1.1K
DC-
NOTES:
1. For Li-Ion, the CHEMISTRY is left floating.
For NiCd/NiMH, the CHEMISTRY is tied to BAT-
2. DC input voltage: 9–16V
3. Charge current: 1A
4. L1: 3L Global P/N PKSMD-1005-470K-1A
Figure 7. Single-Cell Li-Ion, 3-Cell NiCd/NiMH 1A Charger
R3
0.05 W
Minimum Current (Li-Ion Only)
The bq2000 monitors the charging current during the voltage-regulation phase of Li-Ion batteries. Fast charge is
terminated when the current is tapered off to 14% of the maximum charging current.
Once constant-current fast charge has ended, the bq2000 either measures the value of the C_MTO capacitor (in
the case of Nickel batteries) and then proceeds to either top-off or trickle maintenance charge or simply
completes the constant-voltage stage of fast charge (in the case of a Li-Ion cell).
Top-Off and Pulse-Trickle Maintenance Charge
An optional top-off charge is available for NiCd or NiMH batteries. Top-off may be desirable on batteries that
have a tendency to terminate charge before reaching full capacity. To enable this option, the capacitance value
of C_MTO connected between the RC pin and V_CC (Figure 5) should be greater than 0.13µF, and the value of the
resistor connected to this pin should be less than 250kΩ. To disable top-off, the capacitance value should be less
than 0.07µF. The tolerance of the capacitor needs to be taken into account in component selection.
Once top-off is started, the timer is reset and top-off proceeds until the timer expires, V_MCV is reached, or there is
a temperature fault. During top-off, current is delivered to the battery in pulses that occur each second. The fixed
pulse width allows an average current of 1/16 of the fast charge current to be delivered to the battery every
second. The LED is always off during top-off and trickle maintenance charge.
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