Datasheet

BAT+
Q1
FMMT718
D2
ZHCS1000
L1
47 Hm
C9
1000PF
R12
120OHMS
Q2
MMBT3904LT1
C6
47 Fm
D5
MMSD914LT
D3
MMSD914LT
D4
S1A
DC-
R10
1KW
D1
RED
R2
2KW
C3
10 Fm
D6
BZT52-C5V1
R1
100KW
RC
6
LED
3
BAT
4
VSS
2
TS
5
VCC
7
SNS
1
MOD
8
U1
bq2000
C4
0.0022 Fm
R4
12.4K
VCC
C7
4.7PF
C8
0.33 Fm
Q3
MMBT3904LT1
R11
220 W
R6
210KW
C5
10 Fm
BAT-
THERM
CHEMISTRY
R7
200KW
R9
221KW
R5
20KW
C1
0.1
R8
6.81KW
C2
0.1
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
4.L1:3L GlobalP/NPKSMD-1005-470K-1A
3.Chargecurrent:1A
R13
1.1K
R3
0.05 W
DC+
bq2000
SLUS138D –JANUARY 2008–REVISED DECEMBER 2009 www.ti.com
Figure 7. Single-Cell Li-Ion, 3-Cell NiCd/NiMH 1A Charger
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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Product Folder Link(s): bq2000