Tl494 Ltspice Now

The TL494 oscillation frequency ($f_osc$) is determined by two external components: a timing capacitor ($C_T$) and a timing resistor ($R_T$). The oscillator charges $C_T$ with a constant current determined by $R_T$.

The approximate frequency is given by: $$f_osc \approx \frac1.1R_T \cdot C_T$$ In LTspice, this is modeled using a current source charging a capacitor, with a Schmitt trigger to reset the capacitor once the voltage threshold is reached. tl494 ltspice

Let's verify the model by building a simple open-loop Buck converter. The TL494 oscillation frequency ($f_osc$) is determined by

Components needed:

Schematic Netlist Example: If you were to textually describe the connections for the simulation command: Schematic Netlist Example: If you were to textually

X1 IN1 IN2 FB DTC CT RT GND C1 E1 C2 E2 VCC OC VREF IN2_NEG IN1_NEG TL494
V1 VCC GND 15
R_RT RT GND 15k
C_CT CT GND 10n
R_pullup VCC C1 1k
R_load Out 0 10
L1 C1 Out 100u
C1 Out 0 47u

Texas Instruments provides a robust TL494 PSpice model. While PSpice and LTSpice have different syntaxes, you can convert or directly use the .lib file.

Sweep the voltage at pin 4 from 0V to 3V using .step param V_DT 0 3 0.5. Watch the maximum duty cycle drop from 96% to 0%. This is invaluable for transformer-based designs like push-pull or forward converters.