SNVS767E – AUGUST 2000 – REVISED APRIL 2013
Figure 14. Value of Timing Capacitor vs Oscillator Frequency
OUTPUT TRANSISTOR
The output transistor is capable of delivering up to 750 mA with a saturation voltage of less than 0.9V. (see
Collector Saturation Voltage
and
Emitter Saturation Voltage
curves).
The emitter must not be pulled more than 1V below ground (this limit is 0.6V for T
J
≥
100°C). Because of this
limit, an external transistor must be used to develop negative output voltages (see the
Typical
Application). Other configurations may need protection against violation of this limit (see the
section of the
CURRENT LIMIT
The LM2578A's current limit may be referenced to either the ground or the V
in
pins, and operates on a cycle-by-
cycle basis.
The current limit section consists of two comparators: one with its non-inverting input referenced to a voltage
110 mV below V
in
, the other with its inverting input referenced 110 mV above ground (see
The current limit is activated whenever the current limit terminal is pulled 110 mV away from either
V
in
or ground.
Applications Information
CURRENT LIMIT
As mentioned in the functional description, the current limit terminal may be referenced to either the V
in
or the
ground terminal. Resistor R3 converts the current to be sensed into a voltage for current limit detection.
Figure 15. Current Limit, Ground Referred
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