SC4808B Semtech Corporation, SC4808B Datasheet - Page 20

• Manufacturer Part Number: SC4808B
• Description: Sc4808b High-performance Dual Ended Pwm Controller | Semtech
• Manufacturer: Semtech Corporation

Below the benefits from the slope compensation become apparent. The top wave form shows the stable operation
before the perturbation. The second wave form shows the perturbation and the instability caused from it if no slope
compensation is added to the current information. The last wave form shows the slope compensation and the effect of
it. The increase in the slope of the current information results in an early termination of the inductor current, hence a
reduction in the amount of error. As the cycle is repeated, the perturbation is reduced and finally eliminated.
POWER MANAGEMENT
Application Information (Cont.)
I
I
Sense
2005 Semtech Corp.
i
CS
I
L
L
Instable operation
( with perturbation)
Stable operation
(Slope Compensation Added)
Stable operation
( no perturbation)
: Small Inductor current perturbation
: Inductor current
: Summation of Isense and slope compensation, at the CS pin of the SC4808.
: Sensed Mosfet current
I
Sense
I
CS
I
Sense
I
I
L
L
I
L
i
i
L
L
Stable current mode operation with Slope
Compensation
20
D>50%
Note: After a few cycles the perturbation
becomes larger, and causes instability.
Note: After a few cycles the perturbation
disappears and stable operation returns.
SC4808A/B
Error Signal from Error amplifier
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Error Signal from Error amplifier
Error Signal from Error amplifier