Bay Linear, Inc 2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B033
APPLICATION NOTES EXTERNAL
CAPACITOR
To ensure the stability of the B033 an output capacitor of at
least 10
µF (tantalum)or 50µF (aluminum) is required. The
value may change based on the application requirements on
the output load or temperature range.
The capacitor
equivalent series resistance (ESR) will effect the B033
stability. The value of ESR can vary from the type of
capacitor used in the applications. The recommended value
for ESR is 0.5
Ω. The output capacitance could increase in
size to above the minimum value. The larger value of
output capacitance as high as 100
µF can improve the load
transient response.
SOLDERING METHODS
The B033 SOT-223 package is designed to be compatible
with infrared reflow or vapor-phase reflow soldering
techniques. During soldering the non-active or mildly active
fluxes may be used. The B033 die is attached to the heat
sink lead which exits opposite the input, output, and ground
pins.
Hand soldering and wave soldering should be avoided since
these methods can cause damage to the device with
excessive thermal gradients on the package. The SOT-223
recommended soldering method are as follows: vapor phase
reflow and infrared reflow with the component preheated to
within 65
°C of the soldering temperature range.
THERMAL CHARACTERISTICS
The thermal resistance of B033 is 15
°C/W from junction to
tab and 31
°C/W from tab to ambient for a total of 46 °C/W
from junction to ambient. The B033 features the internal
thermal limiting to protect the device during overload
conditions. Special care needs to be taken during continues
load conditions the maximum junction temperature does not
exceed 125
°C.
Taking the FR-4 printed circuit board and 1/16 thick with 1
ounce copper foil as an experiment (fig.1 & fig.2), the PCB
material is effective at transmitting heat with the tab
attached to the pad area and a ground plane layer on the
backside of the substrate. Refer to table 1 for the results of
the experiment.
The thermal interaction from other components in the
application can effect the thermal resistance of the B033.
The actual thermal resistance can be determined with
experimentation. B033 power dissipation is calculated as
follows:
PD = (VIN - VOUT)(IOUT)
Maximum Junction Temperature range:
TJ = Tambient (max) + PD* thermal resistance (Junction-to-
ambient)
Maximum Junction temperature must not exceed the
125
°C.
PO = (10V - 2.85)(105mA) = (7.15)(105mA) = 750mW
50 X 50 mm
35 X 17 mm
16 X 10 mm
Substrate Layout for SOT-223
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