MCP1632-BAESLASHMS datasheet(14/34 Pages) MICROCHIP

14 / 34 page

MCP1632

DS20005254A-page 14

 2013 Microchip Technology Inc.

FIGURE 4-1:

PWM Timing Diagram.

4.6

Slope Compensation

In order to prevent sub-harmonic oscillations that occur

when a Peak Current Mode converter exceeds a 50%

duty cycle, the MCP1632 provides an internal ramp

generator that can be used for slope compensation.

Refer to Figure 4-2 for details about the slope

generator circuit. The amplitude of the generated ramp

signal is 0.9 VPP (typical) and the DC offset value is

770 mV (typical). The impedance of the internal ramp

generator (RG) is 6 ktypical. The amplitude of the

slope compensation ramp can be adjusted by

modifying the value of the RSLOPE resistor. Refer to

Figure 4-3 for details about the slope compensation

ramp signal applied to CS pin. The parameters of the

slope compensation ramp signal can be calculated with

the provided equations.

The MCP1632 device is equipped with a blanking

circuit for the CS pin in order to prevent any false resets

of the RS latch due to noise. However, for certain

applications, it is recommended to place a small value

capacitor (CFILTER) between the CS pin and GND to

provide additional filtering for the current sense signal.

The recommended value ranges from 10 pF to 30 pF.

Use caution, because a higher value may affect the

slope compensation ramp.

FIGURE 4-2:

Slope Compensation

Circuit.

CLK

EA Out

ISENSE

Comp

Out

VDRIVE

VEXT

Ramp

Signal

Oscillator

300/600 kHz

VEXT

Ramp

To PWM

Comparator

RSENSE

RSLOPE

CFILTER

(Optional)

0.9 VPP

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