■Heat Radiation and Reliability
The reliability of an IC is highly dependent on its operating tempera-
ture. Design should pay particular attention to ensuring ample space
for radiating heat.
Be sure to apply silicon grease to the IC before attaching a heatsink,
and to secure it firmly to the heatsink.
Other important items to be considered regarding heat radiation in-
clude air convection during operation.
The reliability of peripheral components such as capacitors and coils
is closely related to temperature. A high operating temperature may
reduce the service life. Exceeding the allowable temperature ma y burn
the coils or damage capacitors. It is impor tant to make sure that the
temperature of output smoothing coils and input/output capacitors do
not exceed their allowable levels during operation. Allow for variation
in the ratings of the coils and minimize heat emission as far as pos-
sible. (For peripheral components, refer to the user manuals.)
■Internal Power Dissipation
PD can be obtained from the following formula.
• With built-in flywheel diode:
(SI-8000L series, STR7000/7100 series)
PD=VO•IO (100 –1)
ηx
• With external flywheel diode:
(SAI series, SI-8000E series, SI-8000S series)
PD=VO•IO(100 –1)–VF•IO(1– VO )
ηxVIN
Efficiency ηx depends on the input/output conditions. The efficiency
characteristics of each product type are provided for reference pur-
poses.
VO: Output voltage
VIN : Input voltage
IO: Output current
ηx : Efficiency(%)
VF: Diode forward voltage
■Heatsink Design
The maximum junction temperature Tj(max) given in the absolute maxi-
mum ratings is specific to each product type and must be strictly
observ ed. Thus , thermal design must consider the conditions of use
which affect the maximum power dissipation PD(max) and the maxi-
mum ambient temperature Ta(max).
To simplify thermal design, the relationship between these two pa-
rameters has been presented in a graph, the Ta-PD characteristic
graph. Thermal design should include these steps:
1. Obtain the maximum ambient temperature Ta(max).
2. Obtain the maximum power dissipation PD(max).
3. Look for the intersection point on the Ta-PD characteristic graph
and determine the size of the heatsink.
The size of the heatsink has no w been obtained. Howe v er, in actual
applications, a 10 to 20% derating factor is introduced. Moreover,
the heat dissipation capacity of a heatsink highly depends on how it
is mounted. Thus, it is recommended to measure the heatsink and
case temperature in the actual operating environment.
The Ta-PD characteristics f or each product type are pro vided f or ref-
erence purposes.
Switching Type - Application Note
71
■Fastening Torque
SI-8000E 0.588 to 0.686[N•m] (6.0 to 7.0[kgf•cm])
SI-8000S
STR7000/7100 0.588 to 0.784[N•m] (6.0 to 8.0[kgf•cm])
■Recommended Silicon Grease
●G746 SHINETSU CHEMICAL INDUSTRIES CO., LTD.
●YG6260 TOSHIBA SILICONE CO., LTD.
●SC102 DOW CORNING TORAY SILICONE CO., LTD.
Please select a silicone grease carefully since the oil in some g rease
can penetrate the product, which will result in an extremely short
product life.
■Others
• Parallel operation can not be performed for increasing current.
• This type IC regulators can not be used for boosting current and
raising voltage.
■Rectifier Diodes for Power Supplies
To rectify the AC input using rectifier diodes in power supplies, use
any of the SANKEN rectifier diodes shown in the following list. (Use
axial type diodes in a center-tap or bridge configuration.)
Regulator Type Diodes
SAI Series
SFPM-62(Surface-Mount Type, V
RM
:200V, I
O
:1.0A)
SI-8000E Series
SI-8200L Series AM01Z(Axial Type, VRM:200V, IO:1.0A)
SI-8400L Series
SI-8000S Series RM 4Z(Axial Type,VRM:200V, IO:3.0A)
RBV -402(Bridge Type, VRM:200V, IO:4.0A)
SI-8300L Series RM10Z(Axial Type, VRM:F200V, IO:1.5A)
SI-8500L Series,
SI-8800L Series AM01Z(Axial Type, VRM:200V, IO:1.0A)
SI-8900L Series
STR7000+ RBV -602(Bridge Type, VRM:200V, IO:6.0A)
SI-8020 Series
STR7100+
FMM-32(Center-tap Frame Type, V
RM
:200V, I
O
:20A)
SI-8020 Series RBV-1506(Bridge Type, VRM:600V, IO:15.0A)