MC33025 Motorola, MC33025 Datasheet - Page 11

• Manufacturer Part Number: MC33025
• Description: High Speed Double-Ended PWM Controller
• Manufacturer: Motorola

V ref to C T . See text on oscillator section for more information.
pin for current mode control. For ramp compensation it is necessary to know the gain of the current feedback loop. The gain can be calculated by:
Additional dead time can be added by the addition of a dead time resistor from
MOTOROLA ANALOG IC DEVICE DATA
The addition of an RC filter will eliminate instability caused by the leading edge spike on the current waveform. This sense signal can also be used at the ramp input
Figure 26. Primary Side Current Sensing
R T
R DT
Figure 23. Dead Time Addition
V ref
C T
4
5
6
9
on the current waveform. This sense signal can also be used at the ramp input pin for
current mode control. For ramp compensation it is necessary to know the gain of the
current feedback loop. If a transformer is used, the gain can be calculated by:
The addition of an RC filter will eliminate instability caused by the leading edge spike
Oscillator
R w
Figure 25. Resistive Current Sensing
I Sense
MC34025 MC33025
A
i
A
+
i
9
+
turns ratio
R Sense
turns ratio
R
w
to be set 10% slower than the sync frequency. This circuit is also used in voltage
mode operation for master/slave operation. The clock signal would be coming
from the master which is set at the desired operating frequency, while the slave
is set 10% slower.
The sync pulse fed into the clock pin must be at least 3.9 V. R T and C T need
5.0 V
0 V
Figure 24. External Clock Synchronization
Figure 27. Primary or Secondary Side
R T
I Sense
Current Sensing
C T
9
4
5
6
R w
Oscillator
I Sense
0
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