APL5603 Datasheet, PDF (10/19 Pages) Anpec Electronics Coropration – Low Dropout 600mA Fixed Voltage Linear Regulator

APL5603
Application Information
Input Capacitor
The APL5603 requires proper input capacitors to supply
surge current during stepping load transients to prevent
the input rail from dropping. Because the parasitic induc-
tor from the voltage sources or other bulk capacitors to
the VIN limits the slew rate of the surge current, it is nec-
essary to place the input capacitors near VIN as close as
possible. Input capacitors should be larger than 0.82µF.
Output Capacitor
The APL5603 needs a proper output capacitor to main-
tain circuit stability and to improve transient response
over-temperature and current. In order to insure the cir-
cuit stability, the proper output capacitor value should be
larger than 1µF. With X5R and X7R dielectrics, 2.2µF is
sufficient at all operating temperatures. Maximum output
capacitor should be less than 330µF to insure the sys-
tem can be powered on effectively.
Layout Consideration
Figure 1 illustrates the layout. Below is a checklist for
your layout:
1. Please place the input capacitors close to the VIN.
2. Ceramic capacitors for load must be placed near the
load as close as possible.
3. To place APL5603 and output capacitors near the load
is good for performance.
4. Large current paths, the bold lines in figure 1, must
have wide tracks.
V_IN
C_IN
V_EN
APL5603
VIN
VOUT
EN
GND
V_OUT
C_OUT
Operation Region and Power Dissipation
The APL5603 maximum power dissipation depends on
the thermal resistance and temperature difference be-
tween the die junction and ambient air. The power dissi-
pation P_D across the device is:
P_D = (T_J - T_A) / θ_JA
where (T_J-T_A) is the temperature difference between the
junction and ambient air. θ_JA is the thermal resistance
between junction and ambient air. Assuming the T =25^oC
A
and maximum T_J=150^oC (typical thermal limit threshold),
the maximum power dissipation is calculated as:
P =(150-25)/260
D(max)
= 0.48(W)
For normal operation, do not exceed the maximum oper-
ating junction temperature of T = 125 ^oC. The calculated
J
power dissipation should be less than:
P =(125-25)/260
D
= 0.38(W)
The GND provides an electrical connection to ground and
channels heat away. Connect the GND to the ground by
using a large pad or ground plane.
Figure 1.
Large ground plane is good for heating. Optimum perfor-
mance can only be achieved when the device is mounted
on a PC board according to the Board layout diagrams
which are shown as Figure2, 3, and 4.
SOT-23-5
V_OUT
C_IN
C_OUT
GND
Figure 2.
DFN3X3-8 For dissipating heat
GND
C_OUT
C_IN
V_IN
V_OUT
Figure 3.
For dissipating heat
GND
SOP-8
C_OUT
V_IN
C_IN
V_OUT
GND
Figure 4.
Copyright © ANPEC Electronics Corp.
10
Rev. A.6 - Mar., 2011
www.anpec.com.tw