Skip to Navigation

2.9.1.1 - PWM Output (16-Bit, Mode 0)

Print pagePrint page Print allPrint all Export allExport all

Outputs a pulse width modulated rectangular wave output. Value passed should be 0-65535, and determines what portion of the total time is spent low (out of 65536 total increments). That means the duty cycle can be varied from 100% (0 out of 65536 are low) to 0.0015% (65535 out of 65536 are low).

The overall frequency of the PWM output is the clock frequency specified by TimerClockBase/TimerClockDivisor divided by 216. The following table shows the range of available PWM frequencies based on timer clock settings.

Note that the clocks above apply to the U3 hardware revision 1.21. With hardware revision 1.20 all clocks are half of those values.

The same clock applies to all timers, so all 16-bit PWM channels will have the same frequency and will have their falling edges at the same time.

PWM output starts by setting the digital line to output-low for the specified amount of time. The output does not necessarily start instantly, but rather waits for the internal clock to roll. For example, if the PWM frequency is 100 Hz, that means the period is 10 milliseconds, and thus after the command is received by the device it could be anywhere from 0 to 10 milliseconds before the start of the PWM output.

If a duty cycle of 0.0% (totally off) is required, consider using a simple inverter IC such as the CD74ACT540E from TI.

tags:

Comments

#1

Submitted by Anonymous (not verified) on Sun, 2012-05-13 12:39.

Dear,

I would like to produce a PWM signal with variable duty cycle. The frequence must be in the 200-100 kHz. Is it possible to use U3? If no did you have some product for this application?

Thank you in advance

Arouna DARGA

#2

Submitted by LabJack Support on Mon, 2012-05-14 08:59.

The U3 can produce PWM signals up to 187.5kHz. Though only in 8-bit PWM mode: http://labjack.com/support/u3/users-guide/2.9.1.2

#3

Submitted by Daniel Roxby (not verified) on Sat, 2011-06-04 06:15.

Am I able to use both the 16 and 8 bit PWM Outputs at the same time? I want to create two PID controllers for a temperature control system I am creating. I am using LabView 2010.

Thanks in advance..

#4

Submitted by LabJack Support on Mon, 2011-06-06 08:56.

Yes, one timer can be used in 8-bit mode while another is in 16-bit mode. Note that they will both be dependent on the TimerClock, so the timer set to 8-bit will output 256 times the frequency of the 16-bit timer.