MC33025 Motorola, MC33025 Datasheet - Page 12

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

current signal by a voltage divider consisting of resistors R 1 and R 2 .
slope necessary. By choosing R M and C M with a larger time constant than the switching frequency, you can assume that its charge is linear. First choose C M , then R M
can be adjusted to achieve the required slope. The diode provides a reset pulse at the ramp input at the end of every cycle. The charge current I M can be calculated
by I M = C M S e . Then R M can be calculated by R M = V CC /I M .
Output
12
This method of slope compensation is easy to implement, however, it is noise sensitive. Capacitor C 1 provides AC coupling. The oscillator signal is added to the
When only one output is used, this method of slope compensation can be used and it is relatively noise immune. Resistor R M and capacitor C M provide the added
R M
C M
Current Sense
Transformer
R w
C f
R f
Figure 29. Current Mode Master/Slave Operation Over Short Distances
Ramp
3
Input
7
Figure 28. Keeps Fig numbering sequence correct
1.25 V
Figure 28A. Slope Compensation (Noise Sensitive)
Figure 28B. Slope Compensation (Noise Immune)
Oscillator
Current Sense
Information
C T
MC34025 MC33025
4
5
6
R 2
R 1
C 1
C T
4
5
6
7
3
R T
V ref
1.25 V
Current Sense
Resistor
4
5
6
Oscillator
Oscillator
MOTOROLA ANALOG IC DEVICE DATA
R f
C M
Output
R M
C f
Ramp
7
3
Input
1.25 V