Tl494 Ltspice [best]

If Pin 1 or Pin 16 is floating or tied incorrectly, the internal error amplifiers might force the feedback pin (Pin 3) to its absolute maximum limit, fully shutting down the PWM comparator. Tie unused error amplifier inputs to safe reference potentials (e.g., non-inverting to GND, inverting to REF). Share public link

The TL494 is a legacy yet industry-standard pulse-width modulation (PWM) control circuit. This paper details the methodology for simulating the TL494 in LTspice, interpreting its internal block diagram, and designing a functional buck converter. We will explore the creation of a behavioral subcircuit model, the theory of dead-time control, and frequency compensation techniques.

Outputs drive MOSFET (simplified) R_GATE OUT1 0 100 R_GATE2 OUT2 0 100

In LTspice, go to File -> New Symbol , draw the 16-pin IC, and name it TL494 . Ensure the pins map to the .subckt nodes: 1IN+: Non-Inverting Error Amp 1 1IN-: Inverting Error Amp 1 FB: Feedback DTC: Deadtime Control CT: Timing Capacitor RT: Timing Resistor GND: Ground C1/E1, C2/E2: Collector/Emitter Outputs VCC: Supply Voltage OC: Output Control (Single/Parallel) REF: Reference Voltage 2IN-, 2IN+: Error Amp 2

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 ). tl494 ltspice

Current sense (optional)

Configure a transient analysis to observe the startup behavior of the chip: Click > Edit Simulation Cmd . Select Transient and set the Stop Time to 5ms . Place a voltage probe on Pin 5 ( CTcap C sub cap T ) to observe the clean, linear sawtooth ramp.

Since Analog Devices (LTspice) does not include the TL494 in its standard library, users must source external subcircuit ( .sub ) and symbol ( .asy ) files.

Output Stage Logic & Dead Time

.ENDS TL494

on this pin, it will completely shut down the outputs. Ensure it is connected firmly to ground for standard test runs. ✅ Summary of TL494 Simulation Setup

fosc=1.2RT×CTf sub o s c end-sub equals the fraction with numerator 1.2 and denominator cap R sub cap T cross cap C sub cap T end-fraction 2. Output Control (Pin 13)

Ground the OC pin for push-pull, or connect to VREFcap V sub cap R cap E cap F end-sub for single-ended. If Pin 1 or Pin 16 is floating

Open LTspice and go to . Change the file type filter to all files and open your saved tl494.lib file.

Output Transistors (Open Collector) Q1 8 104 9 NPN Q2 11 104 12 NPN .MODEL NPN NPN

: The graphical symbol file used to place the component on your LTspice schematic. 2. Map the Files to Your LTspice Directories