UCD3138ARMHR datasheet(22/83 Pages) TI

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UCD3138A

SLUSC66B – MARCH 2015 – REVISED MAY 2015

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5.8.1.4

High Resolution DPWM

Unlike conventional PWM controllers where the frequency of the clock dictates the maximum resolution of

PWM edges, the UCD3138A DPWM can generate waveforms with resolutions as small as 250 ps. This is

16× the resolution of the clock driving the DPWM module.

This is achieved by providing the DPWM mechanism with 16 phase shifted clock signals of 250 MHz. The

high resolution section of DPWM can be enabled or disabled, and the resolution can be defined in several

steps between 4 ns to 250 ps. This is done by setting the values of PWM_HR_MULTI_OUT_EN and

HIRES_SCALE inside the DPWM Control register 1. See the Power Peripherals programmer’s manual for

details.

5.8.1.5

Oversampling

The DPWM module has the capability to trigger an oversampling event by initiating the EADC to sample

the error voltage. The default 00 configuration has the DPWM trigger the EADC once based on the

sample trigger register value. The over sampling register has the ability to trigger the sampling 2, 4 or 8

times per PWM period. Thus the time the over sample happens is at the divide by 2, 4, or 8 time set in the

sampling register. The 01 setting triggers 2X oversampling, the 10 setting triggers 4X over sampling, and

the 11 triggers oversampling at 8X.

5.8.1.6

DPWM Interrupt Generation

The DPWM has the capability to generate a CPU interrupt based on the PWM frequency programmed in

the period register. The interrupt can be scaled by a divider ratio of up to 255 for developing a slower

interrupt service execution loop. This interrupt can be fed to the ADC circuitry for providing an ADC12

trigger for sequence synchronization. Table 5-1 outlines the divide ratios that can be programmed.

5.8.1.7

DPWM Interrupt Scaling/Range

Table 5-1. DPWM Interrupt Divide Ratio

Switching Period

Interrupt Divide Interrupt Divide

Interrupt Divide

Number of 32-MHz

Frames (Assume 1-MHz

Setting

Count

Count (hex)

Processor Cycles

Loop)

128

256

512

1024

1536

2048

2560

3072

127

128

4096

159

160

5120

191

192

6144

223

224

7168

255

256

8192

Specifications

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