MITSUBISHI SEMICONDUCTOR < STANDERD LINEAR IC >
M62281P/FP
GENERAL PURPOSE CURRENT MODE PWM CONTROL IC
(6) CF TERMINAL
Oscillation frequency is set by capacitor connected to CF terminal.
The waveform of CF terminal is triangular one with the ratio of 9:1 for charge-discharge period.
Oscillation frequency is represented as:
f
OSC
=
1
(19.4 * 10
3
* C
OSC
) + (0.4 * 10
-6
)
(Hz)
(7) Attention for heat generation
Although the absolute maximum rating of ambient temperature is spelled out as 85˚C, it is
always annoying to specify the location this temperature refers to because the power
dissipation generated locally in switching regulator is fairly large and the temperature in the
vicinity of the IC varies from place to place.
One of the recommendable ways to solve this problem is to check the teperature on the
surface of the IC.
The difference in temperature between IC junction and the surface of IC package is 30˚C or
less when IC junction temperature is measured by utilizing the temperature characteristics of
p-n junction forward voltage, and the surface temperature by "thermo-viewer" on the condition
that the IC is mounted on the "phenol-base" PC board in normal atomosphere.
This concludes that maximum case temperature (surface temperature of IC package) rating is
100˚C with adequate margin considering the absolute maximum rating of junction temperature
is 150˚C.
(8/9)
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