LMV393: LMV393

Also , what is the effective way of using 2 LMV393 in AND logic?

Hi Swathi,

Kai

Hello Swathi,

Can you provide a schematic? What is your supply votlage? Pull-up resistor value? Actual "High" and "Low" voltages?

At 10mA, the "low" should be around 200-250mV. Remember to also include the pull-up resistor current, too.

I'm not supposed to share the schematic. In the existing schematic we have used the following values.

pull up resistor - 180ohms

Vcc - 5V

high and Low voltage - 5 V and 0V

Also, Is that a good way to connect the O/P of two LMV393 ( in closed loop) directly ?

will that create stability problems ?

Hello Swathi,

You may tie as many open-drain (open collector) outputs together as you wish. They are designed to be "OR'ed.

Never tie a push-pull type output to any other output.

Comparators should not exhibit any "stability" issues with output loading.

A 180 ohms pull-up resistor is a fairly heavy load (27mA). We recommend a pull-up resistor current of around 1mA.

The output is sinking almost 28mA worth of current just from the pull-up resistor. That is before any gate current, The more current the output must sink, the higher the VOL will be.

Try changing the pull-up to 1k.

What are the actual measured VOH and VOL levels?

This is the block level  representation of our circuit.  The comparators are in positive feedback with 1.5K resistor. The problem with this circuit is TRIAC is not turned off for AND logic 0. 

Hello Swathi,

Wow... If there really are two pull-up resistors, then the total pull-up resistor value is 90 ohms! You only need one pull-up resistor.

5V / 90 ohms=55mA that either output would need to sink when low.

55mA is beyond the Figure 3 graph - but it looks like the output low voltage would be about 0.7V (assuming only one output is "low").

I assume the common is on MT2 of the TRIAC?

If so, then assuming the diode drop of MMBD diode, the terminal voltage when "low" would be about 1.4V.

What are you actually measuring at the gate? (Gate to MT2).

Hi Swathi,

have you thought about adding an Opto-Triac driver stage like the MOC3023, e.g.?

Kai