Overview
The UC3843NG4 is a current-mode PWM (Pulse Width Modulator) controller integrated circuit produced by Unitrode, now part of Texas Instruments. This IC is designed to provide efficient and cost-effective solutions for power supply applications, including off-line converters and DC-DC regulators. The UC3843NG4 is part of the UC384x series, which is optimized for operation from 0°C to 70°C, making it suitable for a wide range of environmental conditions.
The device features a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high-gain error amplifier, and a current sensing comparator. These features enable the UC3843NG4 to offer high performance with minimal external components, making it an ideal choice for designers seeking to balance electrical performance and cost.
Key Specifications
| Parameter | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply Voltage | VCC | - | - | 30 | V |
| Output Current | IO | - | - | ±1 A | A |
| Analog Input Voltage | V(ANA) | -0.3 | - | 6.3 | V |
| Error Amp Output Sink Current | ISINK (E.A) | - | - | 10 mA | mA |
| Operating Temperature Range | TA | 0 | - | 70 | °C |
| Storage Temperature Range | TSTG | -65 | - | 150 | °C |
| Reference Output Voltage | VREF | 4.9 | 5 | 5.1 | V |
| Oscillator Frequency | fOSC | 100 | - | 500 kHz | kHz |
| Maximum Duty Cycle | D(MAX) | 95 | 97 | 100% | % |
| Start-Up Current | IST | - | - | 1 mA | mA |
| Operating Supply Current | ICC(OPR) | - | 14 | 17 mA | mA |
Key Features
- Trimmed Oscillator: Allows for precise duty cycle control up to 500 kHz.
- Temperature Compensated Reference: Provides a stable reference voltage across the operating temperature range.
- High Gain Error Amplifier: Ensures accurate feedback and control in the power supply circuit.
- Current Sensing Comparator: Enables external current-to-voltage conversion for current limiting and sensing.
- Under-Voltage Lockout (UVLO): Ensures the IC is fully operational before enabling the output stage, with hysteresis to prevent Vcc oscillations.
- Low Start-Up Current: Less than 1 mA, facilitating efficient bootstrapping from the rectified input of an off-line converter.
- High Current Totem-Pole Output: Capable of driving power MOSFETs or transistors).
Applications
- Off-Line Converters: Suitable for designing efficient and cost-effective off-line power supplies).
- DC-DC Regulators: Ideal for use in DC-DC conversion applications requiring precise control and high efficiency).
- Power Sequencing: Optimized for efficient power sequencing in various power supply configurations).
- Driving Power MOSFETs or Transistors: Capable of handling the high current requirements of power MOSFETs and transistors).
Q & A
- What is the operating temperature range of the UC3843NG4?
The UC3843NG4 operates from 0°C to 70°C).
- What is the maximum duty cycle of the UC3843NG4?
The maximum duty cycle of the UC3843NG4 is approximately 100%).
- What is the purpose of the Under-Voltage Lockout (UVLO) feature?
The UVLO ensures that the IC is fully operational before enabling the output stage, preventing Vcc oscillations during power sequencing).
- How is the oscillator frequency programmed in the UC3843NG4?
The oscillator frequency is programmed using the timing resistor (RT) and capacitor (CT), with the formula Fosc (kHz) = 1.72 / (RT (k) × CT (pf))).
- What is the typical operating supply current of the UC3843NG4?
The typical operating supply current is 14 mA).
- What are the UVLO thresholds for the UC3843NG4?
The UVLO thresholds are 8.5V (on) and 7.9V (off)).
- Can the UC3843NG4 drive power MOSFETs or transistors?
Yes, the UC3843NG4 has a high current totem-pole output capable of driving power MOSFETs or transistors).
- What is the maximum output current of the UC3843NG4?
The maximum output current is ±1 A).
- What is the reference output voltage of the UC3843NG4?
The reference output voltage is 4.9V to 5.1V).
- What are some common applications of the UC3843NG4?
Common applications include off-line converters, DC-DC regulators, and power sequencing in various power supply configurations).
