Overview
The NCP1234AD100R2G is a fixed-frequency current-mode controller designed for flyback converter applications, manufactured by ON Semiconductor. This device is pin-to-pin compatible with the previous NCP12xx families, making it an excellent choice for upgrading existing designs. The NCP1234AD100R2G features Dynamic Self-Supply (DSS), which simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal startup current source during transients. This controller is optimized for high efficiency, low standby power consumption, and robust fault protection, making it suitable for a wide range of power supply applications.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Oscillator Frequency | 65 kHz or 100 kHz | kHz |
| VCC Operation Range | –0.3 to 28 | V |
| Peak Source/Sink Current Drive Capability | ±500 mA | mA |
| High Voltage Pin Range | –0.3 to 500 | V |
| Driver Pin Range | –0.3 to 20 | V |
| Operating Junction Temperature Range | –40 to +150 | °C |
| Storage Temperature Range | –60 to +150 | °C |
| Thermal Resistance (Junction-to-Air) | 115 to 162 | °C/W |
| ESD Capability (Human Body Model) | 2000 V | V |
Key Features
- Fixed-Frequency Current-Mode Operation with Built-In Ramp Compensation: Ensures stable operation and prevents sub-harmonic oscillations.
- Frequency Foldback then Skip Mode for Light Load and Standby Conditions: Maximizes efficiency and reduces switching losses in light load conditions.
- Timer-Based Overload Protection with Latched (Option A) or Auto-Recovery (Option B) Operation: Provides robust fault detection independent of auxiliary winding conditions.
- High-Voltage Current Source with Dynamic Self-Supply: Simplifies the design of the VCC capacitor and ensures clean start-up.
- Frequency Modulation for Softened EMI Signature: Helps in passing EMI limits by spreading out the energy content of frequency peaks.
- Adjustable Overpower Compensation: Allows adjustment of the current sense voltage offset proportional to the input voltage.
- Latch-Off Input for Severe Fault Conditions: Enables direct connection of an NTC for overtemperature protection.
- VCC Operation up to 28 V with Overvoltage Detection: Ensures safe operation with a high supply voltage range.
- 4.0 ms Soft-Start: Gradually increases the peak current during start-up to minimize stress on power components.
- Internal Thermal Shutdown: Protects the controller against self-overheating by shutting down circuitries when the die temperature is too high.
Applications
The NCP1234AD100R2G is particularly well-suited for applications where low part count and high safety are critical. It is ideal for:
- Flyback Converters: Optimized for fixed-frequency current-mode operation, making it suitable for a variety of flyback converter designs.
- Low-Cost Power Supplies: The device's ability to minimize component count without sacrificing safety makes it a cost-effective solution.
- High-Efficiency Power Supplies: Features like frequency foldback and skip mode ensure high efficiency under all load conditions.
- Applications Requiring Robust Fault Protection: The timer-based overload protection and internal thermal shutdown ensure reliable operation in demanding environments.
Q & A
- What is the oscillator frequency of the NCP1234AD100R2G?
The oscillator frequency is available in two versions: 65 kHz and 100 kHz.
- What is the VCC operation range of the NCP1234AD100R2G?
The VCC operation range is from –0.3 V to 28 V.
- What is the peak source/sink current drive capability of the NCP1234AD100R2G?
The peak source/sink current drive capability is ±500 mA.
- How does the Dynamic Self-Supply (DSS) function work?
The DSS function activates the internal startup current source to supply the controller during transients, simplifying the design of the auxiliary supply and the VCC capacitor.
- What is the purpose of the frequency foldback and skip mode in the NCP1234AD100R2G?
The frequency foldback and skip mode maximize efficiency in light load conditions by reducing switching losses.
- How does the timer-based overload protection work?
The overload protection depends only on the FB signal and can operate in either latched or auto-recovery modes, ensuring detection of overload independently of an auxiliary winding.
- What is the purpose of the latch-off input?
The latch-off input allows for severe fault conditions to be detected, including overtemperature protection using an NTC directly connected to the latch pin.
- What is the soft-start duration of the NCP1234AD100R2G?
The soft-start duration is 4.0 ms, during which the peak current is gradually increased to minimize stress on power components.
- How does the internal thermal shutdown protect the controller?
The internal thermal shutdown protects the controller by shutting down all circuitries if the die temperature is too high, allowing the silicon to cool down before attempting to restart.
- Is the NCP1234AD100R2G RoHS compliant?
Yes, the NCP1234AD100R2G is Pb-free, halogen-free/BFR-free, and RoHS compliant.
