Tl494 Ltspice -

is a versatile Pulse-Width Modulation (PWM) control circuit widely used in switch-mode power supplies (SMPS) for its fixed-frequency operation and dual output capability. Integrating it into

is essential for power electronics design, though it requires specific handling due to the lack of a native model in the standard LTspice library. MK Dynamics Availability of TL494 LTspice Models no official LTspice model

provided by the manufacturer (Texas Instruments). Designers typically rely on the following: MK Dynamics Third-Party Subcircuits : Unofficial models, such as those found on MK Dynamics or community forums like LTspice@groups.io , are commonly used. PSPICE Conversions

: Models designed for PSPICE (often found in OrCAD libraries) can be imported into LTspice by manually creating a matching schematic symbol. Subcircuit Structure

: A typical TL494 subcircuit includes internal components like two error amplifiers, a sawtooth oscillator, a dead-time control (DTC) comparator, and output steering flip-flops. How to Integrate TL494 into LTspice

To use a TL494 model in your simulation, follow these steps: Electronics - Hacking the TL494 LTSpice Model - MK Dynamics

Simulating the in LTspice is a common task for power electronics, but it requires specific third-party models because Texas Instruments does not provide an official SPICE model [13, 19, 27]. Finding and Installing the Model Since there is no built-in component, you must source a (subcircuit) or (schematic-based) model from the community: LTspice Groups.io LTspice Groups.io

forum is the most reliable repository for these models [10]. Search for "TL494" in their file section to find optimized versions [17, 23]. Third-Party Repositories : Sites like MK Dynamics

provide subcircuit models, though some users report needing to "hack" or adjust them to get accurate output voltages (some models incorrectly cap output at 4.8V instead of the expected higher saturation level) [7, 22]. Implementation : To use it, place the file in your project directory and add the SPICE directive .include TL494.sub to your schematic [23]. Key Simulation Challenges Convergence & Speed tl494 ltspice

: Users often report extremely slow simulation times (e.g., 10ns per second) when using complex bootstrap driver configurations with the Output Mode Bugs : Some community models struggle with the OUTPUT CTRL

pin; they may only function in push-pull mode even when configured for parallel operation by switching the pin from cap V sub r e f end-sub to GND [3]. Waveform Overlap

: Achieving high-frequency PWM (e.g., 120kHz) can sometimes result in waveform overlap or unexpected offsets in the simulated output [12]. Common Troubleshooting Tips Driver Stage

uses open-collector outputs (Pins 8 and 11). In LTspice, you must provide external pull-up resistors (like a 1k cap V sub i n end-sub

) or a totem-pole driver stage (NPN/PNP pair) to see a switching waveform at these pins [6]. Pin 4 (Dead-Time Control)

: Ensure this pin is tied to GND for maximum duty cycle or biased with a voltage to set a specific dead-time, otherwise, the PWM may not start [8, 15]. Wait for Stabilization

: Start your simulation with a long enough time (e.g., 10ms-20ms) to allow the internal

reference and oscillator to stabilize before checking the PWM output [1]. for a buck converter using the AI responses may include mistakes. Learn more is a versatile Pulse-Width Modulation (PWM) control circuit

Here’s a draft piece for a TL494 SPICE model in LTspice — useful if you’re simulating a PWM controller for switching power supplies.

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Chapter 2: Test Circuit – Buck Converter

Create a schematic (or netlist) named TL494_buck.asc:

* LTspice Circuit: Buck Converter with TL494
VCC VCC 0 DC 15
VIN VIN 0 DC 24


TL494 connections
XTL494 1IN+ 1IN- 2IN+ 2IN- FB COMP CT RT GND C1 C2 VCC OUT1 OUT2 TL494


Oscillator timing
R_RT RT 0 10K
C_CT CT 0 0.01uF   ; ~10kHz


Error amplifier 1: voltage feedback
R1 FB 0 10K
R2 OUT_FB FB 10K   ; voltage divider from output
V_REF 1IN- 0 DC 5   ; reference voltage
R_FB 1IN+ FB 1K


COMP pin compensation
C_COMP COMP 0 0.1uF
R_COMP COMP FB 10K


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


Use OUT1 only in single-ended mode


Power stage
M1 SW GATE 0 0 NMOS (Vto=3)
L1 SW OUT_FB 100uH
C_OUT OUT_FB 0 470uF
R_LOAD OUT_FB 0 10


Freewheel diode
D1 0 SW D1N4148


Current sense (optional)


Not used in this basic example


.model NMOS NMOS (Vto=3 Rd=0.1)
.model D1N4148 D
.tran 0 5m 0 1u
.ic V(OUT_FB)=0
.probe
.backanno
.end

Mastering Power Supply Design: A Complete Guide to the TL494 in LTspice

Setting up PWM regulation:

• Error amp 1: IN1+ (pin 1) = voltage reference (e.g., 2.5V from divider), IN1- (pin 2) = feedback from output.
• Feedback pin (3) is internally connected to error amp outputs (open collector). Add a small pull-up (10k to VREF) if not already in model.

TL;DR — Key points

• TL494 can be modeled in LTSpice with an analog behavioral subcircuit that reproduces its main functions: error amplifier pair, oscillator, PWM comparator with deadtime, current‑limit (via COMP/ILIM), soft‑start and an open‑collector output stage.
• Use averaged PWM or switch‑level model depending on analysis: averaged for control‑loop design and fast convergence; detailed switch model for transient, startup, EMI and switching loss studies.
• Include gate/driver delays, MOSFET Rds(on), and realistic parasitics for credible results.
• Simulate Bode (AC small‑signal) on the error‑amp loop using an averaged model; verify with transient injection on the switch model.

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Frequency formula:

[ f_osc = \frac1R_T \cdot C_T ] (For RT in ohms, CT in farads, f in Hz)
Actual output frequency = ( f_osc ) in single-ended mode, ( f_osc/2 ) in push-pull. Chapter 2: Test Circuit – Buck Converter Create

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