MC34025 ON Semiconductor, MC34025 Datasheet - Page 11

• Manufacturer Part Number: MC34025
• Description: (MC33025 / MC34025) High Speed Single-Ended PWM Controller
• Manufacturer: ON Semiconductor

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 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 V
more information.
Figure 27. Primary Side Current Sensing
R
T
R
Figure 24. Dead Time Addition
DT
V
ref
C
ref
T
to C
4
5
6
9
T
. See text on oscillator section for
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 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:
Oscillator
R
w
Figure 26. Resistive Current Sensing
MC34025, MC33025
I
Sense
http://onsemi.com
A i
A i
+
+
9
turns ratio
turns ratio
11
R Sense
R
w
The sync pulse fed into the clock pin must be at least 3.9 V. R
and C
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.
5.0 V
0 V
T
Figure 25. External Clock Synchronization
need to be set 10% slower than the sync frequency. This
Figure 28. Primary or Secondary Side
R
T
I
Sense
Current Sensing
C
9
T
4
5
6
R
w
Oscillator
I
0
Sense
T