Datasheet

CELLB1
B2 MCV
VR
= N 1
R V
æ ö
´ -
ç ÷
è ø
BAT+
Q1
FMMT718
D2
ZHCS1000
L1
47 Hm
C9
1000pF
R12
120 W
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
bq2000T
C4
0.0022 Fm
R4
12.4kW
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 mF
R8
6.81kW
C2
0.1 mF
NOTES: 1.ForLi-Ion,CHEMISTRY isleftfloating.
ForNiCd/NiMH,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
1.1kW
R3
0.05 W
DC+
bq2000T
www.ti.com SLUS149D –MAY 1999–REVISED JANUARY 2010
BATTERY VOLTAGE INPUT
As shown in Figure 3, a resistor voltage-divider between the battery pack's positive terminal and V
SS
scales the
battery voltage measured at the BAT pin.
For Li-Ion battery packs, the resistor values R
B1
and R
B2
are calculated by the following equation:
(5)
where N is the number of cells in series and V
CELL
is the manufacturer-specified charging voltage. R
B1
+ R
B2
should be at least 200 kΩ and no more than 1 MΩ.
A NiCd or NiMH battery pack consisting of N series cells may benefit by the selection of the R
B1
value to be N–1
times larger than the R
B2
value. This sets the per cell regulation voltage (V
CELL
) equal to V
MCV
. It is critical that
V
CELL
be set high enough that the nickel pack not reach voltage regulation, thus allowing proper termination by
ΔT/Δt. The typical V
CELL
setting for a nickel pack is between 1.7 V and 2 V.
In a mixed-chemistry design, a common voltage-divider is used as long as the maximum charge voltage of the
nickel-based pack is below that of the Li-Ion pack. Otherwise, different scaling is required. See Figure 11 for an
example.
Figure 11. Single-Cell Li-Ion, 3-Cell NiCd/NiMH 1-A Charger
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