NE57611BDH Philipss, NE57611BDH Datasheet - Page 8

• Manufacturer Part Number: NE57611BDH
• Description: Single cell Li-ion battery charger
• Manufacturer: Philipss

Philips Semiconductors
APPLICATION INFORMATION
Figure 6 shows the typical implementation of a single-cell
Lithium-ion battery charger using the NE57611.
Setting the reconditioning charge current
This charging current is needed when the cell voltage is less than
2.15 V. The current is limited by R
should be calculated by:
The reconditioning current should be 1 to 5 mA.
To set the normal maximum charging current, first determine the
desired charge rate for the particular lithium cell in use within the
battery pack. The cell’s datasheet should provide the recommended
maximum rate of charge. Charging at this rate should completely
charge the cell in under 3 hours.
The value of R
found by:
Designing the power section of the battery charger
There are several factors that are important to the design of a
reliable Li-ion battery charger system. These major factors are:
1. The input voltage must not fall below the cell voltage plus the
2003 Oct 15
Single cell Li-ion battery charger
R
R
headroom voltage of the charger circuit. The headroom voltage
for the charger circuit is 0.6 V, which would make the minimum
input voltage about 5.0 V for a Li-ion cell rated at 4.3 V
UV
CS
= [V
= 0.1 V / I
in(max)
CS
that regulates the normal charging current can be
chg(normal)
– V
CELL(min)
+V
–V
IN
IN
] / I
UV
chg(recond)
and its approximate value
10 F
10 k
8
1
Figure 6. Typical charger circuit.
V
ON/OFF
CC
BC807
3
4
V
LV
SS
1 k
NE57611
BCP51
7
DRV
LVEN
2
BAL74
150
8
R
R
PBYR
240CT
CS
UV
and drawing two intersecting lines from the appropriate points on the
2. The maximum input voltage must not exceed the voltage ratings
3. The power rating and the thermal design of the linear pass
The power can then be calculated by:
The criteria for the selection of the PNP power transistor should be:
The choice of power package should be done with the highest
possible power dissipation and at the highest expected ambient
temperature. One can choose a package by referring to Figure 7
X and Y axis.
V
6
5
CS
CELL
maximum. This requirement would also include the troughs of
any ripple voltage riding atop the DC input voltage from a poorly
filtered wall transformer.
of the components in the charging circuit.
transistor must be able to withstand the maximum experienced
headroom voltage at the rated normal charge current. The worst
case condition can be calculated by assuming the cell is at its
lowest voltage (typically 2.3 V) and the input voltage is at its
highest point in its range (typically the DC voltage created at the
highest AC input).
P
V
I
h
P
c
FE
D(max)
CEO
D
> 1.5 I
> P
> 50 @ 1 Amp
> 1.5 V
D(max)
10 F
= (V
charge
IN(max)
IN(max)
V+
V–
– V
CELL(min)
BATTERY PACK
Li-ION
CELL
SL01661
) (I
charge
)
NE57611
Product data