PIC16C782 Microchip Technology Inc., PIC16C782 Datasheet - Page 105

• Manufacturer Part Number: PIC16C782
• Description: 8-bit Cmos Microcontrollers With A/d, D/a, Opamp, Comparators And Psmc
• Manufacturer: Microchip Technology Inc.

TABLE 13-4:
Legend: x = Don’t Care
13.1.2
The PSMC has the capability to operate with either a
single output, or dual alternating outputs. In the single
output mode, the PSMC generates an output pulse on
PSMC1A output only. The pulses are at the pro-
grammed frequency, and are variable between the pro-
grammed minimum and maximum duty cycle limits. In
the dual output mode, the PSMC generates output
pulses which alternate between PSMC1A and
PSMC1B. The pulses generated at each output are
generated at one half of the programmed frequency,
and between 50% of the programmed minimum. and
50% maximum of the output duty cycle. The maximum
duty cycle for either output is 50%.
FIGURE 13-4:
Beginning of PSM cycle
During Pulse Duty Cycle
After Pulse Duty Cycle
2001 Microchip Technology Inc.
PWM Signal
on PSMC1A
pin
SC Switch
on PSMC1B
pin
Voltage across C
SINGLE OR DUAL OUTPUT
Time
PSMC1A OUTPUT SEQUENCE IN PSM MODE USING C1 AND C2 COMPARATORS
t = 0
SLOPE COMPENSATION (SC) SWITCH OPERATION
DC = duty cycle
T = Period
0 = Inactive
t = 15/16T
1 = Active
C1OUT
H
L
x
x
x
x
Preliminary
H = High
C2OUT
H
x
L
x
x
x
13.1.3
An optional feature of the PSMC single output mode is
the ability to configure the PSMC1B output for use as a
slope compensation ramp generator. In this mode, the
PSMC1B output is pulled low for the last 1/16 of each
pulse cycle. Connecting the PSMC1B output to an RC
network, similar to Figure 13-4, results in a positive
going pseudo ramp function. This pseudo ramp func-
tion is useful as an offset function for the loop error sig-
nal in unstable conditions at a duty cycle of greater than
50%.
Note:
L = Low
When the Slope Compensation switch is
enabled (SMCOM = 0, and SCEN = 1), the
S1BPOL bit has no effect (see RC Network
on next page for more detail).
SLOPE COMPENSATION
- On
- Off
PIC16C781/782
PSMC1A Output Signal
V
DD
To Slope
Compensation
Circuit
R
V
SS
No Change
No Change
C
150
0
1
0
0
PSMC1A
PSMC1B
1
0
DS41171A-page 103
V
DD
V
PIC16C78X
SS
SC Switch
Module
PSMC