ePWM
7 - 40 TMS320F2837xD Microcontroller Workshop - Control Peripherals
High Resolution PWM (HRPWM)
High-Resolution PWM (HRPWM)
Significantly increases the resolution of conventionally derived digital PWM
Uses 8-bit extensions to Compare registers (CMPxHR), Period register
(TBPRDHR) and Phase register (TBPHSHR) for edge positioning control
Typically used when PWM resolution falls below ~9-10 bits which occurs at
frequencies greater than ~200 kHz (with system clock of 100 MHz)
Not all ePWM outputs support HRPWM feature (see device datasheet)
PWM Period
Device Clock
(i.e. 100 MHz)
Regular
PWM Step
(i.e. 10 ns)
HRPWM
Micro Step (~150 ps)
HRPWM divides a clock
cycle into smaller steps
called Micro Steps
(Step Size ~= 150 ps)
ms ms ms ms ms ms
Calibration Logic
Calibration Logic tracks the
number of Micro Steps per
clock to account for
variations caused by
Temp/Volt/Process
(fixed Time-Base/2)
The ePWM module is capable of significantly increase its time resolution capabilities over the
standard conventionally derived digital PWM. This is accomplished by adding 8-bit extensions to
the counter compare register (CMPxHR), period register (TBPRDHR), and phase register
(TBPHSHR), providing a finer time granularity for edge positioning control. This is known as
high-resolution PWM (HRPWM) and it is based on micro edge positioner (MEP) technology. The
MEP logic is capable of positioning an edge very finely by sub-dividing one coarse system clock
of the conventional PWM generator with time step accuracy on the order of 150 picoseconds. A
self-checking software diagnostics mode is used to determine if the MEP logic is running
optimally, under all operating conditions such as for variations caused by temperature, voltage,
and process. HRPWM is typically used when the PWM resolution falls below approximately 9 or
10 bits which occurs at frequencies greater than approximately 200 kHz with an EPWMCLK of
100 MHz.
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