lx2208 Microsemi Corporation, lx2208 Datasheet - Page 8

• Manufacturer Part Number: lx2208
• Description: 2 Amp Three Level Lithium Ion Battery Charger
• Manufacturer: Microsemi Corporation

Copyright © 2007
Rev. 1.0, 2007-04-03
L
important to provide a low thermal impedance path from
the thermal pad on the bottom of the LX2208 package to
the ground plane of the circuit board to maximized heat
dissipation. Generally this is accomplished by the use of
multiple thermal vias. This insures the LX2208 stays cool
and can provide the maximum charge current to minimize
the time required to charge the battery.
10µF capacitors (X5R or X7R dielectric) close to the IN
and BAT pins. With long input cables to the adapter or
USB, it is best to use a sheathed cable or twisted wire cable
which is typical of most applications.
placed close to the CMP pin and IN pin; the CMP pin is
located adjacent to the IN pin to facilitate this.
C
the battery charging current during the constant current
charging mode of the battery charging cycle. When the
H/
mode), the charge current is determined by the value of the
HCP programming resistor R
current is determined by the programming current at either
the HCP or LCP programming pins (depending on the state
of H/
The programming current is the HCP or LCP pin voltage
(typically 1.25V) divided by the value of the programming
resistor.
resistor to GND is:
AYOUT
URRENT
In the layout of the Printed Circuit Board (PCB) it is
For latch-up prevention purpose, it is important to place
The CMP 0.47µF capacitor and 1k resistor should be
The LX2208 has two programming resistors to control
L
I
HCP
L
2000
1800
1600
1400
1200
1000
pin is high (selecting the High Current charging
800
600
400
200
); the range of each of these channels is identical.
=
0
R
1.25
TM
0
P
For example, the HCP current with a 7.15k
HCP
ROGRAMMING
=
50
Charge Current vs IHCP (or ILCP)
7.15k
1.25
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
100
=
1
75
R
µA
ESISTORS
IHCP (in uA)
150
HCP
. The maximum charge
200
250
A P P L I C A T I O N N O T E
Analog Mixed Signal Group
300
Microsemi
®
350
2 Amp Three Level Lithium Ion Battery Charger
programming current value of 175µA, the corresponding
maximum charge current is 1A.
the charge cycle is terminated and the battery is determined
to be fully charged. The termination current is determined
by the value of the HCP programming current as
determined by the HCP programming resistor R
value of I
example), the termination current from the chart below can
be seen to be 100mA.
The termination current is always roughly 10% of the
maximum charge current set by the HCP resistor R
Constant Charge Current (in mA)
Using the table above it can be seen that for a
The termination current determines the point at which
Termination Current (in mA)
200
180
160
140
120
100
80
60
40
20
0
0
HCP
P
RODUCTION
= 175µA (as was used in the previous
50
1000
2000
43.3
4.33
460
730
100
200
9.2
92
46
73
Termination Current vs IHCP
100
IHCP (in uA)
150
D
ATA
* R
HCP
200
S
HEET
minimum value
250
169.28k
169.28k
88.67k
15.80k
3.56k*
88.67k
15.80k
3.56k*
9.75k
7.15k
9.75k
7.15k
R
R
HCP
HCP
LX2208
300
HCP
HCP
. For a
.
350
Page 8