Set up the to regulate the output voltage, typically using a voltage divider from the output to 1IN- . Step 3: Running a Transient Simulation To see the PWM signals:
.subckt TL494 VCC GND RT CT DTC FB1 FB2 OUT1 OUT2
+----\/----+ Error Amp 1+ | 1 16 | Error Amp 2+ Error Amp 1- | 2 15 | Error Amp 2- Feedback | 3 14 | REF (5V) Dead-Time Control | 4 13 | Output Control CT | 5 12 | VCC RT | 6 11 | C1 (Collector 1) GND | 7 10 | E1 (Emitter 1) C2 (Coll. 2) | 8 9 | E2 (Emitter 2) +----------+
Simulation steps:
. In simulation, small parasitic capacitances can shift your frequency, so verify the timing ramp at the CT pin (Pin 5) first. 4. Common Use Cases to Simulate tl494 ltspice
Have you simulated the TL494 in LTSpice? Share your convergence tricks and custom models in the comments below.
Texas Instruments provides a robust TL494 PSpice model. While PSpice and LTSpice have different syntaxes, you can convert or directly use the .lib file.
The TL494 shines in push-pull because of its alternating output stages.
13 = OUT1 14 = OUT2
Output Collector/Emitter (Push-Pull or Parallel) VCC (Pin 12): Supply Voltage REF (Pin 14): 5V Reference Output Setting up the Test Circuit (e.g., Buck Converter): Place a Voltage Source (V1) for VCCcap V sub cap C cap C end-sub (e.g., 12V-30V).
Search reputable electronics simulation communities, open-source repositories (such as GitHub), or DIY audio/power electronics forums for a verified TL494 SPICE subcircuit. You will need two files:
Notes: This is a condensed, pragmatic starting point — refine slopes, gains, and the oscillator to match TL494 datasheet values (osc frequency set by RT/CT, deadtime control range, internal reference ≈5V, EA gains, output transistor drive limits).
The TI PSpice model uses charge-controlled switches. Add options reltol=1e-3 vntol=1e-4 to your simulation directive. Set up the to regulate the output voltage,
This is perhaps the most frequent complaint. Users report seeing a constant 12V at the emitter pins with no switching activity.
Purpose: verify startup, soft‑start and current‑limit.
| 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. |