Texas Instruments TMS320DM355 Pulse Width Modulator PWM, 16.1 PWM0/1/2/3 Electrical/Timing Data

TMS320DM355

Digital Media System-on-Chip (DMSoC)

www.ti.com

SPRS463A –SEPTEMBER 2007 –REVISED SEPTEMBER 2007

5.16Pulse Width Modulator (PWM)

The DM355 contains 4 separate Pulse Width Modulator (PWM) modules. The pulse width modulator (PWM) feature is very common in embedded systems. It provides a way to generate a pulse periodic waveform for motor control or can act as a digital-to-analog converter with some external components. This PWM peripheral is basically a timer with a period counter and a first-phase duration comparator, where bit width of the period and first-phase duration are both programmable. The Pulse Width Modulator (PWM) modules support the following features:

∙32-bit period counter

∙32-bit first-phase duration counter

∙8-bit repeat count for one-shot operation. One-shot operation will produce N + 1 periods of the waveform, where N is the repeat counter value.

∙Configurable to operate in either one-shot or continuous mode

∙Buffered period and first-phase duration registers

∙One-shot operation triggerable by hardware events with programmable edge transitions. (low-to-high or high-to-low).

∙One-shot operation triggerable by the CCD VSYNC output of the video processing subsystem (VPSS), which allows any of the PWM instantiations to be used as a CCD timer. This allows the DM355 module to support the functions provided by the DM320 CCD timer feature (generating strobe and shutter signals).

∙One-shot operation generates N+1 periods of waveform, N being the repeat count register value

∙Configurable PWM output pin inactive state

∙Interrupt and EDMA synchronization events

5.16.1PWM0/1/2/3 Electrical/Timing Data

Table 5-46. Switching Characteristics Over Recommended Operating Conditions for PWM0/1/2/3

Outputs(1) (see Figure 5-47and Figure 5-48)

NO.		PARAMETER	DM355		UNIT
			MIN	MAX
1	tw(PWMH)	Pulse duration, PWMx high	P		ns
2	tw(PWML)	Pulse duration, PWMx low	P		ns
3	tt(PWM)	Transition time, PWMx		.05P	ns
4	td(CCDC-PWMV)	Delay time, CCDC(VD) trigger event to PWMx valid		10	ns

(1)P = MXI1/CLKIN cycle time in ns. For example, when MXI1/CLKIN frequency is 24 MHz use P = 41.6 ns.

1

2

PWM0/1/2/3

3

3

Figure 5-47. PWM Output Timing

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