MC34025 ON Semiconductor, MC34025 Datasheet - Page 12

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

This method of slope compensation is easy to implement, however, it is noise sensitive. Capacitor C
signal is added to the current signal by a voltage divider consisting of resistors R
When only one output is used, this method of slope compensation can be used and it is relatively noise immune. Resistor R
capacitor C
can assume that its charge is linear. First choose C
pulse at the ramp input at the end of every cycle. The charge current I
R
Output
M
= V
CC
/I
M
M
R
.
M
provide the added slope necessary. By choosing R
C
Current Sense
M
Transformer
R
C
R
w
f
f
Figure 30. Current Mode Master/Slave Operation Over Short Distances
Ramp
Input
3
7
Figure 29. Keeps Fig numbering sequence correct
Figure 29A. Slope Compensation (Noise Sensitive)
Figure 29B. Slope Compensation (Noise Immune)
1.25 V
Oscillator
Current Sense
Information
C
T
M
MC34025, MC33025
, then R
4
5
6
R
2
http://onsemi.com
R
M
C
C
1
1
T
can be adjusted to achieve the required slope. The diode provides a reset
M
12
and C
4
5
6
7
3
R
T
M
V
can be calculated by I
M
ref
1.25 V
with a larger time constant than the switching frequency, you
Current Sense
Resistor
4
5
6
1
Oscillator
and R
2
.
Oscillator
R
M
f
C
= C
M
Output
1
M
provides AC coupling. The oscillator
R
S
C
M
e
f
. Then R
Ramp
7
3
Input
M
1.25 V
can be calculated by
M
and