Datasheet

L6924U Additional applications information
Doc ID 14716 Rev 2 29/37
9 Additional applications information
9.1 Selecting the input capacitor
In most applications, a 1 µF ceramic capacitor, placed close to the V
IN
and V
INSN
pins can
be used to filter the high frequency noise.
9.2 Selecting the output capacitor
Typically, a 4.7 µF ceramic capacitor placed close to the V
OUT
and V
OUTSN
pin is enough to
keep
voltage control loop stable. This ensures proper operation of battery absent detection
in removable battery pack applications.
9.3 Layout guidelines and demonstration board
The thermal loop keeps the device at a constant temperature of approximately 120 °C which
in turn, reduces I
CHG
. However, in order to maximize the current capability, it is important to
ensure a good thermal path. Therefore, the exposed pad must be properly soldered to the
board and connected to the other layer through thermal vias. The recommended copper
thickness of the layers is 70 μm or more.
The exposed pad must be electrically connected to GND.
Figure 22 shows the thermal
image of the board with the power dissipation of 1 W. In this instance, the temperature of the
case is 89 °C, but the junction temperature of the device is given by the following equation:
Equation 25
Where the R
thJA
of the device mounted on board is 75 °C/W, the power dissipated is 1 W,
and the ambient temperature is 25 °C.
In this case the junction temperature is:
Equation 26
AMBDISSATHJJ
TPRT
+
×
=
−
CT
J
o
10025175 =+×=