Hi,

I have simulated the attached circuit without anything connected to HO output. I have a 5V square wave going into IN and a 10V square wave coming out of HO.

Now I have set the same circuit up on a breadboard and done the same thing but I have a 20V constant voltage coming out of HO.

Not sure why this is the case. Does anyone know what could be the problem here?

 

Hello,

What is the value of the capacitor betwen the Vs and Vb ?
The datasheet shows a 0.1 μF.
Also what is the value of Vcc?
What is the value of Vs?
Vb will be about Vs+Vcc.

Bertus

 

The VB relies on a load being present to operate correctly.
Max.
http://www.silabs.com/support/Pages/bootstrap-calculator.aspx

 

1. The value is 4.7uF electrolytic between Vb and Vs. Didn't see a value of 100nF on the datasheet.
2. VCC is 20V
3. VS was about 20V
4. VB was 19.9V (0.1V drop from diode)

 

The bootstrap capacitor is also sized to the frequency of the PWM.
See link.
Max.

 

1. The value is 4.7uF electrolytic between Vb and Vs. Didn't see a value of 100nF on the datasheet.

Don't most mosfet driver App notes say not to use electrolytic caps for that?

 

As suggested in Tahmid's blog in this thread http://tahmidmc.blogspot.ca/2013/01/using-high-low-side-driver-ir2110-with.html
If an electrolytic is used a small ceramic is used in parallel, if tantalum, it is not needed.
Max.

 

Hi,

I have simulated the attached circuit without anything connected to HO output. I have a 5V square wave going into IN and a 10V square wave coming out of HO.

Now I have set the same circuit up on a breadboard and done the same thing but I have a 20V constant voltage coming out of HO.

Not sure why this is the case. Does anyone know what could be the problem here?

If you are trying to run the IC by itself you need something from Vs to ground or HO won't go to ground.