LF347-N: Triangle Wave Generator

Michael,

Please see the document on Analog Pulse Width Modulation for details on calculating the values of the components to achieve a desired frequency. Additionally, to help verify your design could you please provide supply voltages so we can check the design in simulation?

Best,
Jerry

Hi Jerry,

The supply voltage is +- 12V.

Thank you,

Michael

Michael,

Is there a particular reason you are using a 4 amp design to make a triangle wave as opposed to a 2 amp or 1 amp triangle wave generator?

Best,
Jerry

Hi Jerry,

The design is from a legacy product.  The engineer has moved on to another job.  I assume he was using the first two amps to control the amplitude of the triangle wave?  We need the minimum to be about 3V and about 9V maximum. 

I am open to trying a different design. We are trying to avoid a revision of the PCB.  The LF347 looked like a pin for pin drop in.  I have also ordered the LM324N to try as a pin for pin drop in - due in Friday. 

Any luck with the simulation?

Thanks again,

Michael

Michael,

Could you please tell me what FAULT6_COM is connected to?

Also due to this model being created for a legacy device, there are certain parameters missing which prevent the simulation of this design. I am able to simulate it with newer models. LM324 is also available in PDIP, as well as the BOM cross tool lists the TL3474 as a pin to pin replacement.

Best,
Jerry

Hi Michael,

michael_lf347.TSC

Please note that the simulation will fail with a +/-12V supply voltage.

Kai

Hi Jerry,

FAULT6_COM and FAULT6_NC are the normally closed contacts of a relay.

Thanks for providing another possible alternate to test.  The datasheet actually lists the part as an alternate to MC34074.

I could of sworn I searched Google and TI for alternates.  Anyway, thanks again.

Also, I misspoke about the supply.  We are using +12V and -12V to get 24V.  -12V is used as DC common instead of 0V. 

Thank you,

Michael

Hi Kai,

Thank you for the simulation.  Also, is VG1 +12V.  Your comment made me realize our supply is 24V.

We are using +12V and -12V to get 24V.  -12V is used as DC common instead of 0V.

Is there an APP to open the .TSC files?

Thank you,

Michael 

Kai,

Thank you for the help with simulating the device. My mistake was not including the cap because I did not know where it was connected to, but knew it wasn't simulating because there was some delay missing somewhere which was present when using one of the newer models, I thought this was attributed to the model.

Michael,

You can open .tsc files using TINA TI which I've linked here, as well as the simulation with the LF347 with ±12V supply

tri_wave_lf347.TSC/

Best,
Jerry

Hi Michael,

your scope plot shows a symmetrical triangle wave. This means that the output voltage must swing symmetrically arround the 6.2V reference voltage (V10 in my schematic). And this means that the supply voltages should be 0V and +12V. Only then the output can swing symmetrically arround 6.2V and generate a symmetric triangle wave with equal rise and fall times.

Kai