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2016 Microchip Technology Inc. DS90003140B-page 1
TB3140
INTRODUCTION
A voltage ramp signal finds its purpose in a circuit
application that requires a linear change of voltage. It is
commonly used as a reference signal, slope
compensator or a voltage sweep generator. The
Programmable Ramp Generator (PRG) peripheral
provides voltage ramp signals with no processor
overhead. The PRG can produce a falling ramp, a
rising ramp or alternating rising/falling ramp triggered
from many input sources. A programmable current
source/sink selects the slope rate of the PRG output.
This technical brief provides a straightforward
discussion on the PRG features, method of
configuration and sample applications for different
modes of operation.
BLOCK DIAGRAM
In the block diagram shown in Figure 1, the PRG’s
ramp generation function works by driving a constant-
current into the internal capacitor. The resulting voltage
across this internal capacitor is added to or subtracted
from the voltage input source. The mode of operation
of the ramp output relies mainly on the control of
internal analog switches. The duration between the
moment the ramp starts and stops is determined by the
input timing sources.
FIGURE 1: PRG SIMPLIFIED BLOCK DIAGRAM
Author: Kristine Angelica Sumague
Microchip Technology Inc.
VOLTAGEINPUT
SOURCE
MODESELECTION
INPUTTIMINGSOURCES
Set_falling
TimingSource
PPS
PRGxF
PRGxFPPS
FTSS<3:0>
RPOL
FPOL
EN
SQ
R
Switch
Control
REDG
FEDG
GO
OS
MODE<1:0>
VDD
Voltage
Sources
PRGxIN
INS<3:0>
voltage_ref
SW1
SW2
SW3
RAMPx_out
to
peripherals
PRGCurrentSource
ISET<4:0>
PRGCurrentSink
ISET<4:0>
Set_rising
TimingSource
PPSPRGxR
PRGxRPPS
RTSS<3:0>
Note: SW1 discharges the internal capacitor.
SW2 is closed and SW3 is open during Rising Ramp Generator mode.
SW3 is closed and SW2 is open during Falling Ramp Generator mode.
SW2 and SW3 alternate switching during alternating Rising/Falling Ramp Generator mode.
Programmable Ramp Generator Technical Brief
