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Electronics => Beginners => Topic started by: hussamaldean on July 29, 2018, 09:14:25 am

Title: how to test IR2108 MOSFET driver
Post by: hussamaldean on July 29, 2018, 09:14:25 am
Hi all
is there a way to check if the IC work or not ?
because when I apply 12V to the IC and 5V to HIN and inverter one to LIN the output remains high for both mosfet
this is the circuit from datasheet
(https://i.imgur.com/cV2XRzI.png)
I used normal rectifier diode, 22uF 50V capacitor between Vb and Vs and 100Ohm resistor for the gate of the MOSFET

please help

regards
Title: Re: how to test IR2108 MOSFET driver
Post by: Andy Watson on July 29, 2018, 02:11:14 pm
How are you measuring HO ? Remember that this output is relative to VS. Also, to properly function, the LO mosfet must conduct for a period such that the capacitor between Vb and Vs is charged.
Title: Re: how to test IR2108 MOSFET driver
Post by: hussamaldean on July 29, 2018, 06:02:32 pm
Quote from: Andy Watson on July 29, 2018, 02:11:14 pm
How are you measuring HO ? Remember that this output is relative to VS. Also, to properly function, the LO mosfet must conduct for a period such that the capacitor between Vb and Vs is charged.
the pin and the ground using oscilloscope
I tried the gate of the mosfet and same result
Title: Re: how to test IR2108 MOSFET driver
Post by: alsetalokin4017 on July 29, 2018, 06:46:12 pm
The "LIN" is an inverting input, right, indicated by the line above the letters?
Title: Re: how to test IR2108 MOSFET driver
Post by: hussamaldean on July 29, 2018, 06:56:45 pm
Quote from: alsetalokin4017 on July 29, 2018, 06:46:12 pm
The "LIN" is an inverting input, right, indicated by the line above the letters?

I used NAND gate to get the invert state (my NOT gate is burnt) and still no hope to get the output
Title: Re: how to test IR2108 MOSFET driver
Post by: alsetalokin4017 on July 29, 2018, 07:17:23 pm
OK, let's back up a moment. Forget about the NAND and inverting your input. What happens when you simply apply the +5V signal to _both_ control inputs at the same time? This should produce HO high level and LO low level.

And if you connect both inputs to COM (ground) you should see HO go low and LO go high.
Title: Re: how to test IR2108 MOSFET driver
Post by: alsetalokin4017 on July 29, 2018, 07:26:01 pm
Quote from: hussamaldean on July 29, 2018, 06:02:32 pm
Quote from: Andy Watson on July 29, 2018, 02:11:14 pm
How are you measuring HO ? Remember that this output is relative to VS. Also, to properly function, the LO mosfet must conduct for a period such that the capacitor between Vb and Vs is charged.
the pin and the ground using oscilloscope
I tried the gate of the mosfet and same result

Not ground, measure HO output relative to VS ! Which may or may not be at the same level as COM (ground). Measure LO output relative to COM (ground).
Title: Re: how to test IR2108 MOSFET driver
Post by: hussamaldean on July 30, 2018, 07:05:55 am
Quote from: alsetalokin4017 on July 29, 2018, 07:26:01 pm
Quote from: hussamaldean on July 29, 2018, 06:02:32 pm
Quote from: Andy Watson on July 29, 2018, 02:11:14 pm
How are you measuring HO ? Remember that this output is relative to VS. Also, to properly function, the LO mosfet must conduct for a period such that the capacitor between Vb and Vs is charged.
the pin and the ground using oscilloscope
I tried the gate of the mosfet and same result

Not ground, measure HO output relative to VS ! Which may or may not be at the same level as COM (ground). Measure LO output relative to COM (ground).

well, I will test it back when I get back from the vacation and I will update you