4.1 Introduction
The ePWM peripheral is used to perform a function that is mathematically equivalent to a digital-to-analog
converter (DAC). As shown in
, the effective resolution for conventionally generated PWM is a function
of PWM frequency (or period) and system clock frequency.
PWM
t
T
PWM
T
SYSCLK
PWM resolution (%) = F
/F
x 100%
PWM
SYSCLKOUT
PWM resolution (bits) = Log (T
/T
)
2
PWM
SYSCLKOUT
Figure 4-1. Resolution Calculations for Conventionally Generated PWM
If the required PWM operating frequency does not offer sufficient resolution in PWM mode, you may want to
consider HRPWM. As an example of improved performance offered by HRPWM,
bits for various PWM frequencies. These values assume a MEP step size of 180 ps. See your device-specific
data sheet for typical and maximum performance specifications for the MEP.
Table 4-1. Resolution for PWM and HRPWM
PWM Frequency
Regular Resolution (PWM)
High Resolution (HRPWM)
90 MHz SYSCLKOUT
(kHz)
Bits
%
Bits
%
20
12.1
0.0
18.1
0.000
50
10.8
0.1
16.8
0.001
100
9.8
0.1
15.8
0.002
150
9.2
0.2
15.2
0.003
200
8.8
0.2
14.8
0.004
250
8.5
0.3
14.4
0.005
500
7.5
0.6
13.4
0.009
1000
6.5
1.1
12.4
0.018
1500
5.9
1.7
11.9
0.027
2000
5.5
2.2
11.4
0.036
Although each application may differ, typical low-frequency PWM operation (below 250 kHz) may not require
HRPWM. HRPWM capability is most useful for high-frequency PWM requirements of power conversion
topologies such as:
• Single-phase buck, boost, and flyback
• Multi-phase buck, boost, and flyback
• Phase-shifted full bridge
• Direct modulation of D-Class power amplifiers
High-Resolution Pulse Width Modulator (HRPWM)
378
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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