Overview
The NCP1236DD65R2G is a fixed-frequency current-mode controller developed by onsemi, designed for use in flyback converters. This device is part of the NCP1236 family and is pin-to-pin compatible with the previous NCP12xx series. It 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. The controller is optimized for high efficiency in light load conditions and low standby power consumption, making it suitable for various power supply applications.
Key Specifications
| Characteristic | Unit | Typical | Minimum | Maximum |
|---|---|---|---|---|
| Oscillator Frequency | kHz | 65 | - | - |
| Frequency Foldback Start Threshold | V | 2.0 | 1.8 | 2.2 |
| Frequency Foldback End Threshold | V | 1.35 | 1.22 | 1.48 |
| Minimum Switching Frequency | kHz | 27 | 22 | 32 |
| Peak Source / Sink Current Drive Capability | mA | - | - | 500 |
| Soft-Start Time | ms | 4.0 | - | - |
| VCC Operation Range | V | - | - | 28 |
| Overvoltage Detection Threshold | V | - | - | 26.5 |
| Operating Temperature Range | °C | - | -40 | 125 |
Key Features
- Fixed-Frequency Current-Mode Operation with Built-In Ramp Compensation: Ensures maximum safety and prevents sub-harmonic oscillations.
- Frequency Foldback and Skip Mode: Maximizes performance in light load and standby conditions.
- Timer-Based Overload Protection: Available in latched or auto-recovery modes, with shortened overload timer for increased safety.
- High-Voltage Current Source with Brown-Out Detection and 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 compensation based on the input voltage.
- Latch-Off Input for Severe Fault Conditions: Enables direct connection of an NTC for overtemperature protection.
- Internal Thermal Shutdown: Protects the device against self-overheating.
- Pin-to-Pin Compatibility with Existing NCP12xx Series: Facilitates easy migration and design.
- Pb-Free, Halogen Free/BFR Free and RoHS Compliant: Meets environmental and regulatory standards.
Applications
- AC-DC Adapters for Notebooks, LCD, and Printers: Suitable for various portable and consumer electronics.
- Offline Battery Chargers: Ideal for charging applications requiring efficient and safe power conversion.
- Consumer Electronic Power Supplies: Used in a wide range of household and consumer electronic devices.
- Auxiliary/Housekeeping Power Supplies: Provides reliable power for auxiliary systems and housekeeping functions.
Q & A
- What is the primary function of the NCP1236DD65R2G?
The NCP1236DD65R2G is a fixed-frequency current-mode controller designed for use in flyback converters, ensuring efficient and safe power conversion.
- What are the available oscillator frequencies for the NCP1236?
The NCP1236 is available in 65 kHz and 100 kHz oscillator frequency options.
- How does the frequency foldback feature work?
The frequency foldback feature reduces the switching frequency to minimize losses in light load conditions, and it can further enter a skip mode for extremely low loads.
- What is the purpose of the Dynamic Self-Supply (DSS) function?
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.
- How does the overload protection work in the NCP1236?
The overload protection is timer-based and depends solely on the feedback signal. It can operate in latched or auto-recovery modes, with options for shortened overload timers.
- What is the role of the high-voltage sensing circuitry?
The high-voltage sensing circuitry monitors the input voltage and can turn the controller off if the input voltage is too low (brown-out condition), and it also provides overpower protection.
- Can the NCP1236 be used with standard MOSFETs?
Yes, the NCP1236 features a clamped driver stage that safely limits the voltage on the DRV pin to below 16 V, allowing the use of any standard MOSFET.
- How does the soft-start feature work?
The soft-start feature gradually increases the peak current over a 4.0 ms period at every start-up to minimize stress on power components.
- What is the purpose of the internal thermal shutdown?
The internal thermal shutdown protects the device against self-overheating by shutting down all circuitries if the die temperature becomes too high.
- Is the NCP1236 environmentally compliant?
Yes, the NCP1236 is Pb-Free, Halogen Free/BFR Free, and RoHS compliant.
