MC79M00 Series
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5
Protection Diodes
When external capacitors are used with MC79M00 series
regulator it is sometimes necessary to add protection diodes
to prevent the capacitors from discharging through low
current points into the regulator or from output polarity
reversals. Generally, no protection diode is required for
values of output capacitance less then 10mF. Figure 2 shows
the MC79M15 with the recommended protection diodes.
• Opposite Polarity Protection
Diode D
1 protects the regulator from output polarity
reversals during startup, power off and short-circuit
operation.
• Reverse-bias Protection
Diode D
2 prevents output capacitor from discharging thru
the MC79M15 during an input short circuit or fast switch off
of power supply.
Figure 2. Protection Diodes
Gnd
Gnd
+
-20 V
Input
-15 V
Output
MC79M15
+
1.0 mF 1.0 mF
MBRS140
or Equiv
D1
MBRS140
or Equiv
D2