MAX3221-EP: about charge pump circuit of MAX3221-EP

Vr is about 5.5 V. (This is a fixed voltage threshold implemented by the regulator.)

As far as I can see, that V+ should be Vp.

Hi Minoru,

V+ is output  waveform on the V+ pin (charge pump positive output) it oscillates between values Vr (min-threshold) and Vp (peak voltage) 

Vr ~5.5V - as I mentioned in your comment under the charge pump article.

Vp can be calculated from the equation given in the same article.

So under the normal conditions of the MAX3221-EP

(assuming you are using 5V VCC rec. capacitors) 

VP = ((2*5V * 0.1uF) + (5.5V * 0.47uF)) / (0.57uF) -->  appx. 6.3V

Best,

Parker Dodson

Hi Clemens,

Sorry for the delay in replying.

Thank you for your response.

I understand that Vr is 5.5V for both Vcc=3.3V and Vcc=5V.

Also, changing V+ to Vp gave the desired answer.

My problem solved.

Thank you.

Best regard.

Minoru Awamura

Hi Clemens,

Sorry for the delay in replying.

Thank you for your response.

I understand that Vr is 5.5V for both Vcc=3.3V and Vcc=5V.

Also, changing V+ to Vp gave the desired answer.

My problem solved.

Thank you.

Best regard.

Minoru Awamura

Hi Parker,

Sorry for the delay in replying.

Thank you for your response.

I have calculated V+ as Vp,

which gives me the same answer as you have provided.

My problem solved.

Thank you.

Best regard.

Minoru Awamura