Keep the heavy power traces belonging to MOSFETs, diodes, and transformers entirely distinct from the sensitive control traces around Pins 1, 2, 5, and 6. Use a single-point "star" ground to eliminate ground loops.
Internal 5V reference voltage output. It provides a stable voltage source for error amplifiers and external bias circuits.
The TL494 features two internal operational amplifiers whose outputs are logically ORed together.
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The Error Amplifiers monitor the output voltage. A resistor divider connected to Pin 1 compares the output voltage against the internal 5V reference.
Prevents "shoot-through" (where two transistors are on at once) by enforcing a mandatory "off" period between pulses. Uncommitted Output Transistors:
For a application (where Output Control is grounded), the switching frequency equals the oscillator frequency: Keep the heavy power traces belonging to MOSFETs,
Non-inverting and inverting inputs for Error Amplifier 1. Typically used for voltage regulation. Pin 4 (DTC):
The TL494 comes in a 16-pin package (DIP or SOP). Understanding the function of each pin is crucial for constructing any TL494 circuit diagram. Description IN+1, IN-1 Input terminals for Error Amplifier 1 Feedback terminal, output of both error amplifiers Dead-Time Control; sets minimum dead time Timing capacitor connector Timing resistor connector Ground terminal Collector and Emitter of Output Transistor 1 Emitter and Collector of Output Transistor 2 Supply voltage (input) OUTPUT CTRL Output mode selection (Push-pull or Single-ended) Reference Output IN-2, IN+2 Input terminals for Error Amplifier 2 Core TL494 Circuit Components
Fixed at roughly 50Hz for standard mains inversion. This is achieved using a 100kΩ resistor ( RTcap R sub cap T ) and a 4.7nF capacitor ( CTcap C sub cap T Dead-Time Adjustment (Pin 4): A voltage divider ( R2cap R sub 2 R6cap R sub 6 It provides a stable voltage source for error
A standard TL494 circuit consists of the following key functional blocks: An external capacitor ( CTcap C sub cap T ) and resistor ( RTcap R sub cap T ) set the operating frequency.
Pin 14 provides a stable 5V output (accurate within 5%) used to bias external components and provide a reference for the error amplifiers.