Tl494 - Ltspice

Verify FB pin is not pulled above ~3.5V, and COMP pin voltage is below sawtooth peak.

Unlike many Linear Technology parts, the is a Texas Instruments component, meaning it is not included in the default LTspice library. You must use an external SPICE model ( .subckt ). Step-by-Step Model Implementation:

For permanent installation (so the TL494 appears in the component selection menu): tl494 ltspice

Error Amplifiers (Simplified) E_amp1 100 0 VALUE=LIMIT((V(1)-V(2))*100000, 0, 5) E_amp2 101 0 VALUE=LIMIT((V(16)-V(15))*100000, 0, 5)

Right-click the component, select "Open Symbol", and ensure the "ModelFile" attribute points to your tl494.sub . 3. Basic TL494 Simulation Example: Buck Converter Verify FB pin is not pulled above ~3

| Error Message | Likely Cause | Solution | |---------------|--------------|----------| | "Time step too small" | Fast switching + floating node | Add 1MEG resistors from each output to GND. Reduce maxstep in .tran . | | "Singular matrix" | Missing DC path to GND | Check the voltage feedback divider; ensure error amp inputs are not floating. | | Output always high or always low | Dead-time pin too high (>3V) or wrong oscillator | Set DTC <0.6V for max duty cycle. Verify RT/CT values. | | No oscillation at pin 5 | Missing ic initial condition | Add .ic V(osc_pin)=0.3V or use startup flag. |

To simulate a TL494 circuit in LTSpice, you will need to create a schematic diagram of the circuit and specify the component values and parameters. Here are the general steps to follow: Reduce maxstep in

If your simulation runs but the output is stuck high or low, inspect the following:

) of the TL494 macromodel is dictated by the values chosen for RTcap R sub cap T CTcap C sub cap T . The mathematical relationship is expressed as:

Now for the practical application. We will simulate a buck converter stepping down 24V to 5V at 1A.

If the output oscillates wildly, your feedback compensation network is not optimized. Start by adding a capacitor in parallel with the feedback resistor to create a simple lag compensator.