LM3488QMM National Semiconductor, LM3488QMM Datasheet - Page 11

• Manufacturer Part Number: LM3488QMM
• Description: LM3488/LM3488Q High Efficiency Low-Side N-Channel Controller for Switching Regulators; Package: MINI SOIC; No of Pins: 8; Container: Reel
• Manufacturer: National Semiconductor

The compensation ramp has been added internally in
LM3488. The slope of this compensation ramp has been se-
lected to satisfy most of the applications. The slope of the
internal compensation ramp depends on the frequency. This
slope can be calculated using the formula:
In the above equation, V
compensation ramp. Limits for V
electrical characteristics.
In order to provide the user additional flexibility, a patented
scheme has been implemented inside the IC to increase the
slope of the compensation ramp externally, if the need arises.
Adding a single external resistor, R
increases the slope of the compensation ramp, M
M
C
= V
SL
SL
.F
S
is the amplitude of the internal
FIGURE 3. Compensation Ramp Avoids Sub-Harmonic Oscillation
Volts/second
SL
FIGURE 4. Increasing the Slope of the Compensation Ramp
have been specified in the
SL
(as shown in Figure 4)
C
by :
11
In this equation, ΔV
ΔV
quencies.
SL
versus R
SL
has been plotted in Figure 5 for different fre-
SL
is equal to 40.10
10138813
-6
R
SL
. Hence,
10138811
www.national.com