(SBOA212A) highest output frequency of PWM

Ahmed Amer

Other Parts Discussed in Thread: OPA365, TINA-TI

Hi everyone,

I want to include the PWM as explained in (SBOA212A) here:
PWM generation circuit in my design and I want to know what is the highest frequency of the PWM output this circuit is capable of?

Thanks in advance,

Ahmed

over 3 years ago

+1 Raymond Zhang1 over 3 years ago

TI__Guru* 77541 points

Hi Ahmed,

what is the highest frequency of the PWM output this circuit is capable of?

The PWM output is generated by comparing sine wave with triangle or sawtooth wave, which the modulated PWM is generated. The limiting factor per your question is OPA365, which it has the slew rate of 25V/usec. Since the input Vin is sinewave, the maximum sine frequency OPA365 is able to generate is approx. 1.6MHz (without distortion).

Assume sinewave's amplitude is 2.5Vp (5Vpp), slew rate is SR = 25V/usec, the approx. maximum frequency is calculated to be: f_max = SR/(2.5Vp*2*pi) = 25e6 V/sec/(2.5Vp*6.283) = 1.59MHz.

If you reduce the sinewave's and sawtooth's amplitudes, and use comparator to generate 0-5V modulated PWM, you may increase to higher frequency. You can simulate this via Tina-TI.