Tl494 Ltspice Work Access
The most widely used and respected TL494 SPICE model comes from Valentin Volodin (also known as Bordodynov), who created a comprehensive library of models for LTspice. This library includes the TL494, SG3525A, UC3825, UC3846, UC3875, UC3879, and many other power supply ICs. The library was last updated in January 2021.
(Note: The code above is a highly simplified behavioral model for demonstration. For precision engineering, download the official PSpice model from Texas Instruments and convert the syntax.)
The TL494 can be modeled efficiently in LTspice to predict the real-world performance of vintage and modern switch-mode power supplies.
Below is a functional SPICE model for the TL494 that can be used in LTspice. Copy the text below and save it as a file named TL494.sub in your LTspice library folder (typically C:\Users\<User>\Documents\LTspiceXVII\lib\sub ).
The sharp switching edges inside the macromodel's logic gates can stall the SPICE solver engine. tl494 ltspice
Locate a .subckt file for the TL494. If you have the raw text code, follow these steps: Open a text editor (like Notepad). Paste the TL494 SPICE text code.
Click the button (the running person icon) and probe the following key nodes to ensure the TL494 model behaves like the physical silicon:
If Pin 4 is floating, it may drift high, reducing the duty cycle to zero. Ensure it is explicitly grounded or biased.
The frequency of the internal oscillator is set by the classic formula: The most widely used and respected TL494 SPICE
Based on community experience, here’s a summary of best practices:
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To use the TL494 in LTspice, you must download two files—the subcircuit (.sub) symbol (.asy)
+5V (REF) | [R_DTC] | DTC (Pin 4) +------[R_GND]----+ | v GND Oscillator Frequency (RT and CT) (Note: The code above is a highly simplified
Modulation of output pulses is accomplished by comparing the sawtooth waveform from the oscillator to control signals from the error amplifiers or the DTC input. The output stage is enabled when the sawtooth voltage is greater than these control signals. This mechanism allows for precise duty cycle control from nearly 0% to 49% per output in push-pull mode.
.ENDS TL494
: PWM simulations create steep, fast-switching edges that can choke the SPICE solver. To fix this, change your simulation options. Add the directive .options noopiter or alter the solver in your settings to Alternate ( Control Panel > SPICE > Solver: Alternate ). Error: Outputs are stuck low/high
+--------------------------------------------+ | TL494 | | | | [1] 1IN+ (V_FB) VCC [12] <--+--- VDC (+12V) | [2] 1IN- (V_REF) GND [11] <--+--- GND | [3] FEEDBACK C1 [8] ----> Output Switch 1 | [4] DTC (GND) E1 [9] | [5] CT (To C_ext) C2 [11] ----> Output Switch 2 | [6] RT (To R_ext) E2 [10] | [14] REF (5V Out) OUT_CTRL [13] ----> V_REF (Push-Pull) +--------------------------------------------+ Essential Pin Connections for the Simulation: : Connect Pin 12 ( VCC ) to a DC source. Connect Pin 7 ( GND ) to the SPICE ground ( G ). Oscillator Setup : Connect Pin 5 ( CT ) to a capacitor to ground. Connect Pin 6 ( RT ) to a resistor to ground.
Set to 10m (10 milliseconds) to allow the oscillator and internal reference voltages to settle. Set Time to Start Saving Data to 0 .
