PIC16F753 Datasheet, PDF (145/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F753/HV753
17.0 SLOPE COMPENSATION (SC)
MODULE
The Slope Compensation (SC) module is designed to
provide the necessary slope compensation for fixed
frequency, continuous current, current mode switched
power supplies. Slope compensation is a necessary
feature of these power supplies because it prevents
frequency instabilities at duty cycles greater than 50%.
17.1 Theory of Operation
The SC module works by quickly discharging an internal
capacitor at the beginning of each PWM period. A inter-
nal current sink charges this capacitor at a programma-
ble rate. As the capacitor charges, the capacitor voltage
is subtracted from the reference voltage, producing a lin-
ear voltage decay at the required rate. The current ref-
erence voltage can be supplied by either an I/O pin or by
the buffered output of the FVR peripheral. The FVR
module provides either a fixed voltage or a programma-
ble DAC output. The Reset source can be derived from
either COG output or the synchronized output of either
comparator. Additionally, the Reset source can be
inverted before triggering the Reset. The slope voltage
can be sent to either comparator or the op amp.
The core of the SC module is:
• an on-chip capacitor in series with the voltage
source,
• a shorting switch across the capacitor, and
• a calibrated current sink.
A one-shot pulse generator ensures that the switch is
closed long enough to completely discharge the
capacitor. This typically takes 50 nS.
FIGURE 17-1:
SIMPLIFIED SC MODULE BLOCK DIAGRAM
SCxINS
SLPCIN
0
FVR_buffer1
1
SCxPOL
SLOPE_output
to
peripherals
COG1_output0
COG1_output1
C1OUT_sync
C2OUT_sync
SCxTSS<1:0>
SCxISET<3:0>
00
01
One Shot
10
11
SCxISET * 0.75/15 + 0.2V/µS
1
SCxISET + 1.0V/µS
0
SCxRNG
 2013 Microchip Technology Inc.
Preliminary
DS40001709A-page 145