The Original TL494CN Switching PWM Controller is an industry-standard fixed-frequency pulse-width modulation (PWM) control integrated circuit manufactured by Texas Instruments / ON Semiconductor. Encapsulated in a standard DIP-16 through-hole package, it incorporates all the primary functions required in the construction of switch-mode power supply (SMPS) control circuits on a single monolithic chip. Operating across a wide supply voltage range of 7V to 40V DC, the TL494CN features an on-chip precision 5.0V linear regulator (±5% initial accuracy), a linear sawtooth oscillator capable of frequencies up to 300 kHz, dual uncommitted error amplifiers, an adjustable dead-time control (DTC) comparator, an internal pulse-steering flip-flop, and dual uncommitted output transistors capable of sourcing or sinking up to 200mA each. It is widely utilized in PC ATX power supplies, push-pull DC-DC converters, half-bridge/full-bridge inverters, battery chargers, and high-power motor drivers.

Specifications

• Part Number / Model: TL494CN (Commercial Temperature Range)
• Device Function: Fixed-Frequency Pulse-Width Modulation (PWM) Control Circuit
• Package Type: DIP-16 
• Supply Voltage Range (Vcc / Pin 12): 7.0V to 40V DC (Absolute Max: 41V)
• Collector Output Voltage (Vc1, Vc2 / Pins 8 & 11): Up to 40V DC (Absolute Max: 41V)
• Output Transistor Current (Ic1, Ic2): Continuous: 200mA (Max per transistor) / Peak: 500mA
• Reference Voltage Output (Vref / Pin 14): Typ. 5.0V / Range 4.75V to 5.25V (±5% initial accuracy)
• Reference Output Current: Up to 10mA DC
• Oscillator Frequency Range: 1.0 kHz to 300 kHz (Programmed via external RT and CT)
• Output Control Mode (Pin 13 - Output Ctrl): Ground (0V) for Single-Ended / Parallel mode (0% to 90% Max Duty Cycle); Tied to Vref (+5V) for Push-Pull / Interleaved mode (0% to 45% Max Duty Cycle per output)
• Dead-Time Control Input (DTC / Pin 4): 0V to 3.3V (0V input sets minimum ~3% to 4% internal dead time; 3.3V sets 100?ad time / 0% duty cycle)
• Error Amplifier Common-Mode Input Voltage: -0.3V to (Vcc - 2.0V)
• Error Amplifier Open-Loop Voltage Gain: Typ. 95 dB (at Vout = 0.5V to 3.5V)
• Error Amplifier Unity Gain Bandwidth: Typ. 800 kHz
• Output Saturation Voltage (Common-Emitter Mode): Typ. 1.1V / Max. 1.3V (at Ic = 200mA)
• Output Saturation Voltage (Emitter-Follower Mode): Typ. 1.5V / Max. 2.5V (at Ie = 200mA)
• Total Quiescent Current: Typ. 9.0mA / Max. 15mA (at Vcc = 15V)
• Total Power Dissipation (Pd): 1000mW (at Ta = 25°C)
• Operating Ambient Temperature (Ta): 0°C to +70°C
• Storage Temperature Range (Tstg): -65°C to +150°C
• Thermal Resistance, Junction to Ambient (Rth(j-a)): 70°C/W to 80°C/W
• Pinout Configuration:
  • Pin 1: Non-Inverting Input, Error Amp 1 (1IN+)
  • Pin 2: Inverting Input, Error Amp 1 (1IN-)
  • Pin 3: Feedback / PWM Comparator Input (FEEDBACK / COMP)
  • Pin 4: Dead-Time Control (DTC)
  • Pin 5: Timing Capacitor (CT)
  • Pin 6: Timing Resistor (RT)
  • Pin 7: Ground (GND)
  • Pin 8: Collector Output 1 (C1)
  • Pin 9: Emitter Output 1 (E1)
  • Pin 10: Emitter Output 2 (E2)
  • Pin 11: Collector Output 2 (C2)
  • Pin 12: Operating Supply Voltage (VCC)
  • Pin 13: Output Control Mode (OUTPUT CTRL)
  • Pin 14: Reference Voltage Output (+5.0V VREF)
  • Pin 15: Inverting Input, Error Amp 2 (2IN-)
  • Pin 16: Non-Inverting Input, Error Amp 2 (2IN+)

Features

• Dual Uncommitted Error Amplifiers: Two independent wide-bandwidth error amplifiers allow simultaneous, independent regulation of output voltage and cycle-by-cycle current limiting.
• Flexible Output Configurations: Uncommitted collector and emitter terminals on both output transistors allow configuration as push-pull, half-bridge, single-ended buck/boost, or emitter-follower driver topologies.
• Built-in Pulse-Steering Flip-Flop: Prevents multiple pulsing of either output transistor during high-frequency switching and guarantees alternating half-cycle drive in push-pull mode.
• Adjustable Dead-Time Control (DTC): Pin 4 provides linear adjustment of dead time from minimum 3% up to 100%, preventing shoot-through current in totem-pole and bridge inverter stages.
• Selectable Push-Pull or Parallel Drive: Setting Pin 13 (Output Control) HIGH sets alternating push-pull drive (up to 45% duty cycle each); setting Pin 13 LOW enables parallel single-ended operation (up to 90% duty cycle).
• Precision 5V Reference Generator: On-chip linear reference provides a stable, temperature-compensated 5.0V source to bias voltage divider networks and error amp inputs.

Common Applications

• ATX Desktop & Server Power Supplies: Main PWM controller managing the primary half-bridge power transformer and feedback regulation stages.
• Push-Pull DC-DC Boost Converters: 12V/24V to 220V/310V step-up power inverter boards for solar and off-grid power systems.
• Lead-Acid & Lithium Battery Chargers: Constant-Voltage / Constant-Current (CC/CV) multi-stage charging controllers using dual onboard error amplifiers.
• High-Power Pure & Modified Sine Wave Inverters: High-frequency front-end DC bus voltage boost controllers.
• Industrial Switch-Mode Power Supplies: Forward, flyback, and full-bridge industrial power converter racks.

Usage Tips

• Oscillator Calculation Formula: Set the switching frequency using: f_osc = 1 / (RT × CT) for single-ended mode, or f_out = 1 / (2 × RT × CT) per output in push-pull mode. Recommended values are RT = 1kΩ to 500kΩ and CT = 470pF to 10µF (typical RT = 10kΩ to 100kΩ, CT = 1nF to 10nF).
• Configuring Output Control (Pin 13): For push-pull, half-bridge, or full-bridge circuits, wire Pin 13 directly to Pin 14 (+5V Vref) to enable alternating flip-flop drive. For single-ended buck, boost, or parallel drive, connect Pin 13 directly to Pin 7 (GND).
• Soft-Start Circuit Implementation: To implement power-on soft-start, connect an electrolytic capacitor (e.g., 10µF) between Pin 14 (Vref) and Pin 4 (DTC), and place a 10kΩ resistor from Pin 4 (DTC) to Pin 7 (GND). Upon power-up, DTC starts at 5V (0% duty cycle) and smoothly decays to 0V (full duty cycle).
• Terminating Unused Error Amplifiers: If using only Error Amp 1 for voltage feedback, disable Error Amp 2 cleanly to avoid oscillation by tying Pin 16 (2IN+) to Pin 7 (GND) and Pin 15 (2IN-) to Pin 14 (Vref).
• Reference Noise Bypass: Place a 100nF low-ESR ceramic capacitor directly across Pin 14 (Vref) and Pin 7 (GND) to suppress high-frequency switching noise on the internal voltage reference rail.

Datasheet