lm5027mhx National Semiconductor Corporation, lm5027mhx Datasheet - Page 21

• Manufacturer Part Number: lm5027mhx
• Description: Voltage Mode Active Clamp Controller
• Manufacturer: National Semiconductor Corporation

Oscillator
The oscillator frequency is generally selected in conjunction
with the system magnetic components and any other aspects
of the system which may be affected by the frequency. The
R
Sync Capability section. If the required frequency tolerance is
critical in particular application, the tolerance of the external
resistor and the frequency tolerance specified in the Electrical
Characteristics table must be considered when selecting the
R
T
T
resistor selection equation is specified in the Oscillator and
resistor.
FIGURE 12. UVLO Circuit with Shutdown Control
FIGURE 13. Typical COMP Configuration
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Voltage Feedback
The COMP pin is designed to accept a current input typically
from an opto-coupler. A typical configuration is shown in
ure
connected to the COMP pin and the collector is connected to
the REF pin of the LM5027. When the output voltage is below
regulation, no current flows into the COMP pin and the
LM5027 operates at maximum duty cycle. At the secondary
side, VOUT is compared to a reference by the error amplifier
which has an appropriate frequency compensation network.
The amplifier output drives the opto-coupler, which in turn
drives the LM5027 COMP pin current mirror.
13, where the emitter of the opto-coupler transistor is
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