## Overview of the TL493CD The **TL493CD** is a pulse-width-modulation (PWM) control circuit designed primarily for power-supply control. It is very similar to the industry-standard TL494 but includes specific modifications, such as an internal current-limit amplifier and variations in the output control logic. The "CD" suffix indicates that the device is housed in a **SOIC (Small Outline Integrated Circuit)** package and is rated for a commercial temperature range (0°C to 70°C). --- ### Key Internal Components The TL493CD integrates several functional blocks onto a single chip to manage a switch-mode power supply (SMPS). | Component | Function | | :--- | :--- | | **Error Amplifiers** | Two high-gain amplifiers used to monitor voltage and current. They compare feedback to a reference. | | **5V Reference** | An internal linear regulator that provides a stable 5.0V output (Vref) for external use. | | **Oscillator** | Generates a sawtooth waveform. Frequency is set by an external Resistor ($R_T$) and Capacitor ($C_T$). | | **Dead-Time Comparator** | Provides a fixed or variable "off-time" to prevent simultaneous conduction of output transistors. | | **Output Transistors** | Two uncommitted transistors that can be used in push-pull or parallel (single-ended) mode. | | **Steering Flip-Flop** | Directs the PWM signal to either Output 1 or Output 2 for push-pull applications. | --- ### Technical Specifications | Parameter | Value (Typical) | | :--- | :--- | | **Supply Voltage ($V_{CC}$)** | 7V to 40V | | **Output Current (Source/Sink)** | 200 mA | | **Reference Voltage** | 5.0 V (±5% tolerance) | | **Oscillator Frequency Range** | 1 kHz to 300 kHz | | **Package Type** | SOIC-16 | --- ### Pin Configuration Summary The TL493CD typically uses a 16-pin layout. Below is the functional mapping for key pins: 1. **Pin 1 & 2:** Non-inverting/Inverting inputs for Error Amplifier 1 (usually Voltage Control). 2. **Pin 3:** Feedback/Compensation. 3. **Pin 4:** Dead-Time Control (DTC). 4. **Pin 5 & 6:** $C_T$ and $R_T$ (Timing components). 5. **Pin 7:** Ground. 6. **Pin 8 & 11:** Collector outputs ($C1$, $C2$). 7. **Pin 9 & 10:** Emitter outputs ($E1$, $E2$). 8. **Pin 12:** $V_{CC}$ (Power Input). 9. **Pin 13:** Output Control (Toggles between Push-Pull and Single-ended). 10. **Pin 14:** Reference Output (5V). 11. **Pin 15 & 16:** Error Amplifier 2 inputs (usually Current Control). --- ### Operating Principle The TL493CD controls the output power by modulating the **duty cycle**. 1. The **Oscillator** creates a ramp signal. 2. The **Error Amplifier** compares the output voltage of the power supply to the 5V reference. 3. The **PWM Comparator** compares the Error Amplifier output to the Oscillator ramp. 4. When the ramp voltage exceeds the error voltage, the output transistors switch states. --- ### Design Example: Oscillator Frequency The output frequency for a single-ended application is calculated using the following formula: ```math f = \frac{1.1}{R_T \times C_T} ``` *Note: For push-pull applications, the frequency per output transistor is half of the oscillator frequency.*