Application Note for Regulator ICs
■ Temperature and Reliability
Reliability of an IC is generally heavily dependent on
operating temperature. Heat radiation must be fully
considered, and an ample margin should be given
to the radiating area in designing heatsinks. When
mounting ICs on heatsinks, always apply silicone
grease and firmly tighten. Air convection should
actively be used in actual heat dissipation. The
reliability of capacitors and coils, the peripheral
components, is also closely related to temperature.
A high operating temperature may reduce the
service life. Exceeding the allowable temperature
may cause coils to be burned or capacitors to be
damaged. Make sure that output smoothing coils
and input/output capacitors do not exceed their
allowable temperature limit in operation. We
recommend, in particular, to provide an ample
margin for the ratings of coils to minimize heat
generation.
generally used. Moreover, the heat dissipation
capacity of a heatsink is heavily dependent on how
it is mounted. It is therefore important and
recommended to measure the heatsink and case
temperature in actual operating environments.
■ Setting DC Input Voltage
Observe the following precautions when setting the
DC input voltage:
• VIN (min) must be at least the set output voltage
plus dropout voltage for the dropper type. It must
be at least the recommended lowest input
voltage for the switching type.
• VIN (max) must not exceed the DC input voltage of
the electrical characteristics.
■ Screw Torque
Screw torque should be between 0.588 to 0.686
[N • m] (6.0 to 7.0 [kgf • cm]).
■ Power Dissipation (PD)
1. Dropper Type
PD
2. Switching Type
100
=
IO • [VIN (mean) - VO]
■ Recommended silicone grease
Volatile type silicone grease may produce cracks
after elapse of long term, resulting in reducing heat
radiation effect.
Silicone grease with low consistency (hard grease)
may cause cracks in the mold resin when screwing
the product to a heatsink.
VO
PD
Efficiency
Refer to the efficiency characteristics.
=
VO • IO (
- 1) - VF • IO (1 -
)
VIN
depends on input/output conditions.
: Efficiency
VO : Output voltage
VIN: Input voltage
IO : Output current
VF : Diode forward voltage
Type
G746
Suppliers
Shin-Etsu Chemical Co., Ltd.
■ Heatsink Design
YG6260
SC102
GE Toshiba Silicones Co., Ltd.
The maximum junction temperature Tj (max) and the
maximum case temperature Tc (max) given in the
absolute maximum ratings are specific to each
product type and must be strictly met. Thus,
heatsink design must be performed in consideration
of the condition of use which affects the maximum
power dissipation PD (max) and the maximum
ambient temperature Ta (max). To facilitate heatsink
design, the relationship between these two
parameters is presented in the Ta-PD characteristic
graphs. Heatsink design must be performed in the
following steps:
Dow Corning Toray Silicone Co., Ltd.
■ Others
This product may not be connected in parallel.
The switching type may not be used for current
boosting and stepping up voltage.
1. Obtain the maximum ambient temperature Ta
(max) (within the set).
2. Obtain the maximum power dissipation PD
(max).
3. Identify the intersection on the Ta-PD charac-
teristic graph and obtain the size of the
heatsink to be used.
The size of a heatsink has been obtained. In actual
applications, a 10 to 20% derating factor is
7
SANKEN [ SANKEN ELECTRIC ]
