: Tie Pin 4 ( DTC ) directly to ground for minimum dead-time (
For advanced users, you can go beyond a fixed subcircuit and create a behavioral model of the TL494’s oscillator. One user shared an LTspice behavioral model for the TL494 oscillator that was configurable based on external R and C with the formula f = 1.2 / (R * C) . It also allowed for variable blanking time and peak voltage, giving the user complete control over the simulation of the oscillator core—useful for co-simulation or educational purposes.
Limit the maximum time-step in your simulation configuration directive. A command like .tran 0 2m 0 10n forces a tight 10-nanosecond window, preventing the solver from jumping past critical switching edges. tl494 ltspice
The TL494 has 16 pins, which must be correctly mapped in your simulation. 1IN+ / 1IN- (Pin 1/2): Error Amplifier 1 Input FB (Pin 3): Feedback/Compensation DTC (Pin 4): Dead-time Control CT / RT (Pin 5/6): Timing Capacitor & Resistor GND (Pin 7): Ground
A unique feature of the TL494 is the Dead-Time Control pin. It sets the minimum dead time (off-time) for the output transistors. This prevents "shoot-through" current in push-pull or bridge topologies. : Tie Pin 4 ( DTC ) directly
| 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. |
is a high-performance SPICE simulation software developed by Analog Devices, ideal for simulating switching converters due to its speed and accuracy. While LTspice excels at analog circuit modeling, simulating specialized ICs like the TL494 often requires importing external SPICE models. Step 1: Obtaining the TL494 Model for LTspice Limit the maximum time-step in your simulation configuration
LTSpice doesn’t include a built-in TL494 device, so you have three realistic options:
Instead of building from scratch, leverage existing work: