Tl494 Ltspice [patched] May 2026

The TL494 is a classic PWM control IC widely used in power electronics, such as inverters and DC-DC converters. While it is not a native component in the standard LTspice library, it can be simulated by importing third-party SPICE models. 1. TL494 Core Architecture

Sawtooth oscillator on CT pin (pin 7)

• Replace switches with a controlled current/voltage source that outputs D·Vin across inductor.
• Model PWM as a gain of (Vcomp→duty): K_pwm ≈ 1/Vramp (Vramp = CT ramp amplitude). For TL494, Vramp ≈ Vref amplitude; set K_pwm = Kc (adjust per subckt).
• Build power stage small‑signal transfer Gvd(s) from duty to Vout (use linearized inductor/capacitor impedances).
• Multiply Gvd(s) by PWM gain and error amplifier gain to get open‑loop. Insert type‑II (or III) comp network on COMP pin.
• Run .ac analysis to plot magnitude/phase, tune crossover ~ 1/5 to 1/10 of switching frequency (for discrete converters use <fs/10).

Example 1 — Single‑switch buck converter (switch‑level TL494)

Purpose: verify startup, soft‑start and current‑limit. tl494 ltspice

Step 4: The LTSpice Simulation Commands

.tran 0 5m 0 1u startup
.step param Load Rload list 5 1 10

The Model Code: 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 TL494 is a classic PWM control IC